Modulation of Autonomic Function and Heart Rate Variability by Transcutaneous Spinal Cord Stimulation and Physical Therapy in Individuals with Chronic Spinal Cord Injury

Modulation of Autonomic Function and Heart Rate Variability by Transcutaneous Spinal Cord Stimulation and Physical Therapy in Individuals with Chronic Spinal Cord Injury | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Modulation of Autonomic Function and Heart Rate Variability by Transcutaneous Spinal Cord Stimulation and Physical Therapy in Individuals with Chronic Spinal Cord Injury Adriana Pliego-Carrillo, Daniella Pinto, Alejandra Méndez, Marina Girault, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8398767/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Spinal cord injury causes motor, sensory, and autonomic impairments. Transcutaneous spinal cord stimulation (tSCS) has shown potential to improve autonomic regulation, particularly cardiovascular and bladder control. Heart rate variability (HRV) serves as a non-invasive marker of autonomic balance, reflecting modulation of cardiac sympathetic and parasympathetic activity. The purpose of this study was to evaluate the effect of combined tSCS and physical therapy (tSCS + PT) on HRV and autonomic function metrics in chronic spinal cord injury. Methods. Eight participants (2 with tetraplegia, 6 with paraplegia) received tSCS at 30 Hz targeting T11–L1 or C5–T1, depending on injury level. Each underwent two tSCS + PT sessions per week for 12 weeks, followed by a 4-week washout period. Autonomic assessments included the Autonomic Standard Evaluation Form (ASAF), Neurologic Bladder Symptoms Score (NBSS), blood pressure, heart rate, SpO2%, and core temperature. Electrocardiograms were recorded pre- and post-tSCS + PT at baseline, 12, and 16 weeks. Results. Baseline effects of tSCS + PT revealed increased time-domain HRV parameters, suggesting enhanced cardiac parasympathetic activation (PSA). After 12 weeks, these parameters decreased, suggesting reduced cardiac PSA and enhanced sympathetic activation (SA). Similar results were found with frequency-domain parameters. Time-and frequency-domain parameters tended to return toward baseline after the 4-week therapy suspension. Two commonly reported HRV parameters, SDNN and RMSSD, showed large effects (g = 1.64, CI 95% [0.30, 2.98], and g = 1.23, CI 95% [0.11, 2.42], respectively) at 12 weeks when comparing pre- vs. post-tSCS + PT. Moderate, subject-related differences across evaluations were found in ASAF and NBSS (p > 0.05). Physiological metrics across time points did not show statistically significant differences (p > 0.05). Physiological metrics across time points did not show statistically significant differences (p > 0.05). Conclusions Combined tSCS + PT elicited improvements in autonomic clinical measures, without statistically significant changes in time-domain or frequency-domain HRV parameters. Nonetheless, trends and size effect in SDNN and RMSSD suggested that tSCS + PT induced midterm SA and a transient PSA immediately post-tSCS + PT. The partial recovery of HRV after tSCS withdrawal indicates that the observed autonomic changes were therapy-related. spinal cord injury transcutaneous spinal cord stimulation non-invasive neuromodulation transspinal stimulation autonomic function physical therapy heart rate variability parasympathetic activity sympathetic activity tetraplegia paraplegia Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Background The sequelae of spinal cord injury (SCI) compromise motor, sensory, and autonomic functions. Global data from 1990 to 2021 indicate an increase in the prevalence and incidence of this condition, and, since there is no clinical treatment that effectively reverses or mitigates post-SCI dysfunction, complications in the chronic stage of SCI result in high medical care costs and diminish patients' quality of life [ 1 ]. Furthermore, these complications can prevent the patient from undergoing physical therapy (PT) due to autonomic dysfunction symptoms, including orthostatic hypotension, sudden increase in blood pressure (BP) caused by peripheral stimulation, loss of sphincter control, inappropriate sweating, and altered thermoregulation [ 2 ]. The evaluation of the autonomic nervous system (ANS) is not routinely or clinically exhaustively evaluated, posing a challenge for specialists due to the need for standardized assessment tools [ 3 ]. However, heart rate variability (HRV) analysis, an indirect assessment of cardiac autonomic balance, provides insight into the relative predominance of sympathetic (SA) versus parasympathetic activation (PSA) influencing cardiac and vascular function. Time-domain and frequency-domain HRV parameters have been widely investigated and characterized for their association with sympathetic and parasympathetic branches of the autonomic nervous system in the regulation of cardiac function [ 4 ]. For example, while a reduction in time-domain parameters (RMSSD, SDNN, and pNN50) suggests a predominance of sympathetic cardiac activity, an increase in high-frequency (HF) activity (0.15–0.4 Hz), derived from the R-R interval power spectrum, from the QRS complex, is associated with parasympathetic modulation mediated by vagal activity [ 5 ]. Previous evidence indicates that a decrease in HRV occurs within the 24 months following SCI [ 6 ]. In addition, differences in HRV parameters have been consistently reported in the literature for injured subjects compared to uninjured controls, showing that HRV is lower in individuals with SCI, as revealed by 24-hour Holter monitoring [ 7 ]. In addition, reductions in low-frequency (LF) and HF components have been reported in individuals with SCI compared to controls [ 8 ]. Similarly, Rodriguez et al. (2016) reported significantly lower LF and LF/HF ratios in paraplegia and tetraplegia than in able-bodied individuals during a fatigue test; on the other hand, HF did not show significant differences between groups [ 9 ]. These results suggested the presence of cardiac autonomic dysfunction, particularly in tetraplegia, as reported by Malmqvist et al. (2015) in acute SCI [ 6 ]. The combination of postural maneuvers with electrocardiographic (ECG) recordings contributes to the study of cardiovascular autonomic responses in SCI, complementing evidence from resting HRV parameter analysis. For instance, Park et al. (2025) investigated the HRV in two groups of individuals with complete and incomplete SCI, categorized by the presence or absence of orthostatic hypotension (OH). They found that the OH group exhibited lower index values, such as RMSSD and SDNN, in the supine position, suggesting a reduced influence of cardiac PSA [ 10 ]. The evidence suggests that, in patients with SCI, the interplay between SA and PSA in cardiac modulation is impaired, depending on the complexity of the physical task. Particularly, the diminished sympathetic tone, evidenced by the high OH prevalence and generalized low mean BP values, could reflect a state of critical cardiovascular vulnerability. In addition, low values of HRV assessment appear similar to those observed in high-risk conditions such as myocardial infarction or sudden cardiac death [11–13In addition, experts have suggested that metrics typically considered 'normal' in the general population do not apply directly to individuals with SCI [ 14 , 15 ] underscoring the need to develop parameters tailored to their condition. Transcutaneous spinal cord stimulation (tSCS) is a non-invasive neuromodulation technique that delivers electrical current via electrodes placed on the skin. It has shown improvements in cardiovascular function by normalizing BP during the sit-up test [ 16 ] and mitigating autonomic dysreflexia [ 17 ]. In addition, tSCS benefits urinary [ 18 – 20 ] and anorectal functions [ 21 ]. Although the results above show promise for improving autonomic function, the effects of tSCS combined with physical therapy (tSCS + PT) on HRV and on immediate and midterm cardiovascular sympathetic and parasympathetic parameters in individuals with SCI have not yet been described. In this study, our primary goal was to evaluate the effect of pre- and post-tSCS + PT on HRV at baseline, 12 weeks, and after suspending the intervention for 4 weeks to assess the persistence of effects (16 weeks). Secondarily, we aimed to evaluate changes in autonomic function using validated scales and physiological parameters. 2. Methods This study was a prospective, single-arm trial. The protocol was approved by the Research and Ethics Committees of Universidad Anáhuac México (ID 202209, approval date: May 31, 2022). All procedures were conducted at the Movement Analysis Laboratory, Universidad Anáhuac México. Individuals aged 18–30 years of either sex were included if they were at least one year post-SCI and had an injury below the C3 level of any severity, as classified by AIS. Subjects were excluded if they presented with pressure ulcers, unresolved infections, unhealed or recent fractures, demyelinating processes, or any other condition that prevented participation in PT or exposure to electrical stimulation. Participants were excluded from the final analysis if they missed two consecutive sessions or more than four sessions in total. Eight male subjects with paraplegia (p004, p007, p008, p009, p010, and p011) and 2 subjects with tetraplegia (p012 and p013) were included in the study after providing informed consent. According to the AIS, six participants were classified as A, one as B, and one as C (Individual sensory and motor scores are included in Appendix B, Table B1, Individual baseline AIS scores). Six participants had thoracic injuries between T2 and T10, and two patients had cervical injuries. The median age of the subjects was 28.5 years (range 21–50), and the median of years after SCI was 2.5. All SCIs were caused by trauma. The demographic and clinical characteristics of the participants are shown in Table 1 . Heart rate (HR), BP, SpO2%, and core temperature (°C) were recorded at the beginning and end of each tSCS + PT session. The Autonomic Standard Assessment Form (ASAF) and the Neurogenic Bladder Symptom Score (NBSS) were applied at Baseline, 12, and 16 weeks as shown in Fig. 1 A. tSCS was applied by two self-adhesive electrodes used as cathodes (2.5 cm diameter, Medstar) that were placed in the intervertebral spaces T11-12 and T12-L1 for subjects with paraplegia, and in C5-6 and C6-7 in subjects with quadriplegia, while two rectangular electrodes (4 x 8 cm, MedStar) used as anodes were placed on the iliac crests for subjects with paraplegia and over the middle third of the clavicles in subjects with quadriplegia (Fig. 1 B). The stimulation current for each participant was determined based on spinal cord motor-evoked potentials (SCMEPs) recorded at baseline. Briefly, with the same electrode configuration described above, current pulses were applied at 0.2 Hz in 5 mA steps until SCMEPs were observed in at least one registered muscle. The muscles recorded bilaterally were the medial portion of the deltoid, biceps brachii, triceps brachii, and common flexor digitorum in the case of individuals with quadriplegia (n = 2). For subjects with paraplegia (n = 6), the muscles recorded were rectus femoris, biceps femoris, tibialis anterior, and lateral gastrocnemius. The signals were recorded at a sampling rate of 10 kHz (PowerLab, ADInstruments®) and visualized in real time within a 50-ms window. Finally, the current intensity corresponding to the SCMEP threshold of the first responsive muscle in each patient was reduced by 10%. This value was applied at 30 Hz (symmetrical biphasic pulses, 280 us per phase, DS8R Digitimer®) during tSCS + PT in both tetraplegia and paraplegia. Subjects received two tSCS + PT sessions per week for 12 weeks. The intervention was then suspended for 4 weeks, and subjects were reevaluated (Fig. 1 A). Subjects with paraplegia underwent trunk control exercises in a sitting position on a Bobath table while subjects with tetraplegia performed arm and hand exercises in their wheelchairs (Appendix A). Exercises were performed according to each patient's capabilities and were supervised by a physical therapist. tSCS + PT sessions lasted 30–40 minutes. Table 1 Demographic and clinical characteristics of the participants. Patient ID Sex and age (years old) AIS-grade Neurological level Years post-SCI SCI cause P004 Male – 50 A T10 1.2 Trauma from a falling weight directly onto the spine P007 Male – 20 A T2 2 Gunshot injury P008 Male – 40 A T4 8 Motorcycle accident P009 Male – 24 B T3 1 Motorcycle accident P010 Male – 31 A T4 1.7 Gunshot injury P011 Male – 36 A T10 5 Gunshot injury P012 Male – 26 C C3 3 Car Accident P013 Male – 26 A C4 4.1 Gunshot injury An Electrocardiogram (ECG) was recorded for 5 minutes in the 5th intercostal space along the midclavicular line corresponding to the V4 precordial lead with the subject lying in supine position (sampling frequency 1 kHz, ADInstruments®) (Fig. 1 C). ECG recordings were performed before (pre-tSCS + PT) and immediately after tSCS (post-tSCS + PT) at a) Baseline to assess acute effects; b) after 12 weeks of receiving tSCS + PT, to assess mid-term effects, and c) after 16 weeks (4 weeks after suspending the intervention to assess persistence of effects). Participants were requested to refrain from consuming caffeinated and alcoholic beverages at least 24 h prior to ECG recordings. The protocol timeline is shown in Fig. 1 A. 2.1 Data analysis BP, HR, SpO2% and core temperature (°C) were taken at the beginning and after each tSCS + PT session. Mean arterial pressure (MAP) was determined according to the formula: MAP = DBP + (1/3) * (SBP - DBP), where DBP is the diastolic blood pressure and SBP is the systolic blood pressure. The values corresponding to 4, 8, 12, and 16 weeks of the intervention were averaged to assess whether significant changes or trends occurred over time. ECG preprocessing began with a visual selection of a continuous 5-minute segment of the main recording to exclude motion artifacts. Subsequently, the Pan-Tompkins algorithm was applied in MATLAB to extract the R-R interval sequence. The latter was analyzed using Kubios HRV Scientific (Kubios, Finland) [ 4 ], estimating the typical time-domain variables (Mean RR, SDNN, RMSSD, NN50, pNN50, RRTI, TINN), frequency-domain variables (VLF peak, LF peak, HF Peak, Total Power, and the LF/HF ratio), SI (Baevsky’s Stress Index), Parasympathetic Nervous System (PNS), and Sympathetic Nervous System (SNS) indexes for sympathetic/parasympathetic balance behavior in cardiac regulation. In patient p010, no baseline ECG recordings were obtained due to a residual scar at the ECG electrode placement site. After 3 months, scar healing allowed for the ECG recordings. Patient p009 did not return for the 16-week follow-up evaluations. Since only two subjects with tetraplegia were recruited, no comparisons were made between this group and the paraplegia group. The results for each variable were analyzed as a single group. 2.2 Statistical Analysis Descriptive statistics were obtained for quantitative variables. The ANOVA or Kruskal-Wallis test was used, depending on the data distribution, after applying the Shapiro-Wilk test. Next, the Equal Variance Test (Brown-Forsythe) was performed. If differences in the median or mean values were observed, a post-hoc analysis was carried out using Dunn's test with Bonferroni correction. The effect size for paired comparisons was calculated using Cohen’s d and the bias-corrected Hedges’ g. Subsequently, 95% confidence intervals (CI 95%) were computed. Hedges’ g values greater than 0.40 were considered to represent a large effect among the comparisons. Statistical tests and plots were performed in SigmaPlot 14.0 (SigmaStat). 3. Results 3.1 Autonomic evaluations The ASAF evaluations at baseline, 12, and 16 weeks are shown in Table 2 . In three subjects (p004, p007, and p008), the general and sacral autonomic sections remained unchanged at 16 weeks. Two participants (p009 and p011) increased by 1 pt. in the general autonomic section, while a decrease of 1 pt. occurred in p012. Four individuals (p009, p010, p012, and p013) showed an increase of at least 1 pt. in the sacral autonomic section; however, in p012, this increase was not sustained at 16 weeks. No significant differences were found when comparing the total score at baseline (median 11.0, P25-P75: 10.75-11.0), 12 (median 11.0, P25-P75: 10.75-11.0), and 16 (median 11.0, P25-P75: 10.75-11.0) weeks in the general autonomic function (p > 0.05) (Table 2 ). Similarly, no significant statistical differences were found when comparing the scores of sacral autonomic functions at baseline (median 3.5, P25-P75: 1.5-4.0), 12 (median 3.5, P25-P75: 2.5–4.5), and 16 (median 3.5, P25-P75: 1.75–5.25) weeks (p > 0.05) (Table 2 ). Regarding the Hedges’ g values for the General Autonomic Section, these were < 0.4 in the comparisons of Baseline total scores vs. 12 weeks (g = 0.34, CI 95% [-0.593, 1.273]) and Baseline vs. 16 weeks (g = 0.0, CI 95% [-0.927, 0.927]). Similarly, when comparing the Hedges’ g values for the total scores of the Sacral Autonomic Section, values < 0.4 were found for Baseline vs. 12 weeks (g = -0.197, CI 95% [-1.126, 0.732]) and Baseline vs. 16 weeks (g = -2.05, CI 95% [-1.133, 0.723]). Individual ASAF scores are included in the Appendix B, Table B2, ASAF individual scores at baseline; Table B3, ASAF individual scores at 12 weeks, and Table B4, ASAF individual scores at 16 week. Table 2 ASAF scores at baseline, 12, and 16 weeks. Patient ID Baseline 12 weeks 16 weeks Total Score General Autonomic Section Total Score Sacral Autonomic Section Total Score General Autonomic Section Total Score Sacral Autonomic Section Total Score General Autonomic Section Total Score Sacral Autonomic Section P004 11 4 11 4 11 4 P007 10 7 10 7 10 7 P008 11 3 11 3 11 3 P009 9 4 10 6 10 6 P010 11 4 11 4 11 5 P011 11 0 11 0 12 0 P012 12 2 11 3 11 2 P013 11 0 11 1 11 1 Median P25 , P75 SD 11.0 10.75 11.0 0.88 3.5 1.5 4.0 2.32 11.0 10.75 11.0 0.46 3.5 2.5 4.5 2.32 11.0 10.75 11.0 0.64 3.5 1.75 5.25 2.44 ASAF, Autonomic Standard Assessment Form. The results at baseline, 12, and 16 weeks of the total NBSS for each participant are shown in Fig. 2 . Regarding urinary function, three subjects (p007, p009, and p010) showed improvement in NBSS at 16 weeks compared to baseline. One participant (p004) improved considerably at 12 weeks, and then the score increased markedly in the final evaluation. In this case, the patient reported a urinary infection between 12 and 16 weeks, which likely contributed to the worsening of the NBSS. In one individual, the total NBSS remained unchanged (p013), and 3 subjects (p012, p008, and p011) worsened their scores at 16 weeks. Specifically, p008 and p012 used a permanent urinary catheter and reported urinary infections during the intervention. p011 had a stoma and reported greater scores at 12 weeks due to an increase in storing, combined with an increase in voiding sensation. No significant differences were found when comparing the total NBSS at baseline (median, 14.5; P25-P75: 9-29.5), 12 (median, 18.0, P25-P75: 10.0-26.75), and 16 weeks (median, 19.5; P25-P75:14.0-24.5) (p > 0.05). Hedges’ g values for the NBSS resulted in no size effect in the comparisons of baseline total scores versus 12 weeks (g = -0.043, CI 95% [-0.970, 0.884]) and baseline versus 16 weeks (g =-0.08, CI 95% [-1.011, 0.843]). Individual NBSS scores are included in Appendix B, Table B5, NBSS individual scores at baseline, 12 and 16 weeks. The MAP, HR, SpO2(%), and core temperature (°C) mean values across time points are shown in Fig. 3 . Data were obtained pre- and post-tSCS + PT at each session and averaged every 4 weeks to allow comparisons. MAP and HR (pre- and post-tSCS + PT) showed a slight tendency to increase after 4 weeks compared to baseline. In particular, the increase in HR was sustained through the final evaluation at 16 weeks (Fig. 3 ). SpO2 (%) and body core temperature (°C) remained stable across all time points. No significant differences were found between pre- and post-tSCS + PT values at any time point for any parameter (MAP, HR, SpO2 (%), and core temperature), as shown in Fig. 3 . 3.2 Heart Rate Variability HRV time- and frequency-domain evaluations and corresponding indexes were performed pre-and post-tSCS + PT at baseline, 12, and 16 weeks (Fig. 4 and Table 3 ). At baseline, the acute effect of tSCS + PT showed a slight increase in HRV in the post-tSCS + PT compared to pre-tSCS in all time-domain parameters (Fig. 4 A-D, Table 3 ). Consistently, the SI showed a slight decrease, suggesting a decrease in sympathetic activity immediately after stimulation (Fig. 4 F). Interestingly, the midterm effect of pre-tSCS + PT after 12 weeks on HRV time-domain parameters decreased compared to baseline values, suggesting a consistent cardiac SA (Fig. 4 A-D, Table 3 ). However, the post-tSCS + PT effect on HRV at this point indicated a greater PSA predominance than pre-tSCS + PT. At 16 weeks, time-domain parameters (Fig. 4 A-D, Table 3 ) and the SI index (Fig. 4 F) showed a tendency to revert to baseline values. The observed HRV pattern supports the hypothesis that alterations in HRV are primarily induced by the intervention (tSCS + PT), with transient effects dissipating after ceasing the intervention for 4 weeks. When analyzing the time-domain HRV parameters at the pre-tSCS + PT (Baseline) and pre-tSCS + PT (12 and 16 weeks) periods, the results suggest that, in the resting state, individuals with SCI generally exhibit an exacerbation of sympathetic cardiovascular modulation. This predominance appears to be further intensified following exposure to tSCS + PT, leading to increased regularity of heartbeats, as evidenced by a reduction in HRV dispersion at 12 weeks (Fig. 4 A-D, Table 3 ). In our view, three events merit attention in time-domain HRV parameters: (1) during the pre-tSCS in the baseline and 12 weeks evaluation, a pronounced increase in HRV parameters is observed as a direct effect of tSCS + PT, suggesting plastic adaptations in autonomic regulatory pathways in response to tSCS exposure, particularly after the 12 weeks intervention; (2) in the mid-term response, following 12 weeks of continuous tSCS + PT, a reduction in the dispersion of beat-to-beat interval values is evident, indicating enhanced regularity in cardiac rhythm, particularly in the pre-tSCS-PT evaluation; and (3) after suspending the intervention for four weeks, HRV parameters tended to return to baseline levels, suggesting the transient nature of the intervention’s physiological effects. The pre-tSCS + PT effect analysis is particularly interesting, showing a change in the ratio percentage for the pNN50, a metric associated with cardiac parasympathetic influence, of 35.5% at Baseline, 160.3% at 12 weeks, and − 44% at 16 weeks, further supporting the notion that the observed effects are attributable to the tSCS + PT intervention (Fig. 4 D and Table 3 ). Based on the duration of the ECG recordings, the frequency-domain analysis focused on parameters within the LF and HF bands. The peak values of the power spectrum with-in the LF and HF bands, associated with sympathetic and parasympathetic cardiovascular modulation, respectively, showed no changes in median values when comparing pre-tSCS + PT and post-tSCS + PT recordings at baseline, 12, and 16 weeks (Table 3 ). Consequently, no significant differences were found among time points (p > 0.05). The power of the LF and HF bands, which provide more comprehensive information on sympathetic and parasympathetic cardiac modulation respectively, exhibited a change ratio, shown as pre-tSCS + PT- post-tSCS + PT/pre-tSCS + PT of 0.229 at Baseline, 1.539 at 12 weeks, and 0.137 at 16 weeks for LF, and 0.248 at Baseline, 2.775 at 12 weeks, and − 0.239 at 16 weeks for HF. Consistent with the time-domain parameters, a more pronounced shift toward parasympathetic modulation was observed for the immediate response (pre vs. post-tSCS + PT) at 12 weeks, as reflected by the increase in HF power (Table 3 ). However, the overall midterm effect of the intervention appears to suggest a slight enhancement in sympathetic predominance. This observation is further supported by the increase in the LF/HF ratio at 12 weeks compared to both Baseline and 16 weeks, indicating a shift towards sympathetic dominance following the intervention (Fig. 4 E and Table 3 ). Regarding the HRV indexes, the comparison of pre- and post-tSCS + PT values at baseline and after 12 weeks revealed a shift toward zero (Fig. 4 F-H and Table 3 ), indicating a trend toward values observed in healthy individuals [ 22 ]. Interestingly, the comparison of pre-tSCS + PT values indicated a less parasympathetic (negative) and more sympathetic (positive) influence on heartbeat regulation, with this difference in cardiac autonomic predominance more pronounced at 12 weeks than at baseline or 16 weeks (Fig. 4 F-H and Table 3 ). However, no significant differences were found when comparing SI, SNS, and PNS indexes at any time point in both pre-and post-tSCS + PT (p > 0.05) (Fig. 4 F-H and Table 3 ). Table 3 HRV analysis: time- and frequency-domains, SI and PNS and SNS indexes in pre- and post-tSCS + PT at baseline, 12, and 16 weeks. Parameter Baseline Acute effects 12 weeks Midterm effects 16 weeks Persistance of effects p value Time-domain Median P25 P75 Pre- tSCS Post- tSCS Pre- tSCS + PT Post- tSCS + PT Pre- tSCS Post- tSCS Mean RR (ms) 808.00 701.50 915.50 965.50 873.00 1383.00 827.00 683.00 867.00 836.00 745.00 890.00 830.00 756.00 954.00 823.5 753.00 943.00 p > 0.05 SDNN (ms) 38.00 18.35 48.42 41.05 20.62 56.65 29.4 19.7 31.80 38.20 30.50 48.50 40.85 15.27 61.27 37.90 20.15 59.92 p > 0.05 NN50 (ms) 44.00 0.75 112.5 49.50 0.75 130.25 14.00 3.00 31.00 32.00 28.00 73.00 61.50 0.00 107.5 33.50 0.00 117.75 p > 0.05 RMSSD (ms) 33.00 10.92 55.50 38.40 13.52 66.75 21.20 17.30 29.90 30.80 26.40 39.90 39.55 13.47 55.72 27.70 12.82 61.12 p > 0.05 pNN50 (%) 12.18 0.15 37.80 16.52 0.21 45.50 3.20 0.69 8.59 8.33 7.16 19.25 17.32 0.00 34.69 9.61 0.00 36.28 p > 0.05 RR TI (%) 7.99 6.82 11.79 10.44 7.71 12.71 7.62 4.66 9.83 10.21 8.04 12.45 10.12 7.61 13.40 8.22 6.23 15.22 p > 0.05 TINN (ms) 184.5 91.00 233.25 205.50 101.25 277.00 157.00 98.00 178.00 198.00 140.00 251.00 199.50 76.75 274.50 190.50 98.50 297.25 p > 0.05 Frequency-domain LF peak 0.05 0.04 0.07 0.06 0.05 0.07 0.04 0.04 0.05 0.05 0.04 0.07 0.05 0.04 0.08 0.06 0.04 0.09 p > 0.05 HF peak 0.26 0.25 0.30 0.23 0.21 0.24 0.26 0.16 0.35 0.16 0.15 0.24 0.24 0.17 0.29 0.20 0.16 0.24 p > 0.05 LF power 732.5 315.25 1088.25 900.5 447.75 1122.25 245 182 477 622 469 1088.5 389.5 145.5 1385.75 443 250.5 1357 p > 0.05 HF power 523.5 77 1039.75 653.5 158 1441.5 111 74.5 250.5 419 242 652 480 189.5 1169.5 365.5 87.25 1357 p > 0.05 LF/HF 1.26 1.14 4.45 1.19 0.70 2.67 2.63 1.10 7.04 2.80 1.11 3.57 1.20 0.67 6.98 2.21 0.84 8.20 p > 0.05 Indexes SI 11.80 8.07 22.25 10.00 6.97 19.92 14.50 12.50 21.30 11.00 7.90 14.40 9.80 7.30 26.47 13.40 7.20 19.55 p > 0.05 PNS -0.77 -1.52 0.47 -0.22 -1.14 0.70 -1.12 -1.69 -0.87 -0.75, -1.08 -0.48 -0.44 -1.28 0.26 -0.95 -1.69 0.25 p > 0.05 SNS 0.94 -0.39 2.34 0.30 -0.67 1.54 1.25 0.96 3.02 0.80 0.19 1.33 0.37 -0.24 2.89 1.28 -0.19 2.66 p > 0.05 Hedges’ g was calculated to estimate the effect size for pre- and post-tSCS + PT measures at baseline, 12 weeks, and 16 weeks for time- and frequency-domain HRV parameters. Only Hedges’ g values > 0.4 are reported next, across all possible pair-wise comparisons. For SDNN, a large effect was found at 12 weeks for pre- vs. post-tSCS + PT (g = 1.64, CI 95% [0.30, 2.98]). Comparable findings were obtained for RMSSD at 12 weeks, pre-vs post-tSCS + PT (g = 1.23, CI 95% [0.11, 2.42]). For the remaining parameters, high variability was observed; consequently, the mean differences were not statistically significant at the 95% confidence level. 4. Discussion SCI is a complex condition that impairs motor and sensory functions below the lesion level, as well as autonomic functions involving the cardiovascular and bronchopulmonary systems, thermoregulation, sweating, sphincter control, and sexual function. Autonomic complications, such as orthostatic hypotension and autonomic dysreflexia, can limit the patient’s ability to engage in physical activity and rehabilitation, ultimately reducing quality of life and life expectancy [ 23 ]. In recent years, tSCS + PT has shown significant functional improvements following SCI. While most studies have focused on motor outcomes, fewer have addressed autonomic function, particularly cardiac autonomic modulation. The present study is the first to investigate both the baseline (acute) and mid-term (12 weeks) effects of tSCS + PT on HRV and autonomic function, as well as the persistence of these effects 4 weeks after the intervention ended (a total of 16 weeks) in individuals with paraplegia and tetraplegia. Importantly, HRV parameters were evaluated alongside validated measures of autonomic function, providing a novel and integrative contribution to understanding the overall impact of this therapeutic intervention. Regarding autonomic outcomes, the most prominent improvements were observed in sacral autonomic function, particularly in gastrointestinal function and bladder filling sensation in three participants (p009, p010, and p013) (Appendix B, Tables B3, B4, and B5). For p009 and p010, these improvements were also reflected in reduced NBSS values (Fig. 2 , Appendix B, Table B5). Importantly, p010 and p007 both achieved NBSS reductions of more than 5 points, representing a clinically significant change [ 24 ]. Although in this study we did not employ quantitative parameters of autonomic function, our results confirm previous findings that tSCS at 30 Hz benefits motor, sensory, and autonomic systems [ 20 , 25 – 31 ]. Although no statistically significant differences were found between time points in the time-domain HRV indexes, tSCS + PT appears to have increased sympathetic influence on cardiac modulation when comparing pre-tSCS values at Baseline vs. 12 weeks, meaning that a potential decrease in parasympathetic cardiac modulation is reflected in the changes observed in RMSSD, NN50, and pNN50 at 12 weeks. After this period, a tendency to return toward Baseline values by 16 weeks was observed (Fig. 4 and Table 3 ). Serra-Añó et al. (2015) reported that individuals with paraplegia exhibited lower time-domain HRV values than able-bodied controls; however, physical activity further reduced these values. Although current evidence remains inconclusive, it is hypothesized that, in paraplegia, a more pronounced sympathetic drive may represent a beneficial cardiovascular adaptation rather than an indicator of increased risk [ 14 ]. In the frequency domain, previous evidence has shown significant differences in the LF band between individuals with SCI and able-bodied controls. In addition, the HF band exhibited greater variability, particularly between tetraplegic and paraplegic patients [ 32 ]. In our study, we computed the power values for the LF and HF bands, representing the peak amplitude and the area under the curve. Baseline pre-tSCS + PT responses revealed a marked increase in both LF and HF power compared to post-tSCS + PT. This increase was also reflected in the LF/HF ratio, with the most notable change occurring at 12 weeks. In contrast, after 12 weeks, results showed a reduction in LF and HF power in both pre- and post-tSCS-PT, followed by a moderate elevation at 16 weeks (pre-tSCS + PT). Interestingly, our results resemble those obtained in SCI subjects after two sessions of 32 minutes of transcranial direct current stimulation, showing a significant increase in the LF/HF coefficient and a decrease in the HF band (33). The simultaneous power decrease at midterm and the acute increase in both bands suggest a joint enhancement of baroreflex and parasympathetic modulation. Again, as with time-domain parameters, frequency-domain results indicated increased sympathetic modulation. However, these frequency-domain findings may instead reflect a vagal tone reinforcement due to tSCS + PT. The increase in HRV observed when comparing pre-tSCS + PT to post-tSCS + PT at 12 weeks is similar to the increase in SDANN observed in 50 individuals with SCI over a 5-week period immediately after injury. The significant increase in this SDANN, measured using a Holter monitor, was interpreted as a compensatory cardiovascular response, modulated by a plastic changing system formed by the damaged axons aimed at restoring function [ 6 ]. The combination of physical exercises performed during PT sessions and tSCS has attracted significant interest, as evidenced by a recent protocol integrating tSCS with upper-limb exercise [ 33 ]. In this sense, we do not exclude the possibility that physical activity may have contributed to the changes observed in HRV parameters. Individuals with tetraplegia and paraplegia who exercised using a standing frame exhibited lower HR values and higher HF power, suggesting enhanced parasympathetic modulation associated with upright posture and active engagement [ 34 ]. Interestingly, with tSCS, the parasympathetic response appears to be stimulation frequency-dependent, as SDNN and pNN50 increased significantly in able-bodied volunteers with 45 Hz stimulation, while HF power decreased at 7 Hz [ 35 ]. Considering the above, further research is needed to determine whether interventions aimed at reinforcing vagal tone in SCI, such as physical exercise or targeted autonomic maneuvers, increase HRV or whether the observed changes predominantly reflect a shift toward sympathetic modulation. The lack of statistically significant differences in time-domain and frequency-domain parameters in our study may be attributed to the small sample size and/or the limited duration of the intervention. Considering the latter, 12 weeks of exposure to tSCS (two sessions per week) might not be sufficient to induce profound changes in cardiac autonomic modulation. Previous studies have emphasized that frequency-domain analysis may be low in sensitivity to short-term interventions and therefore recommend the use of nonlinear methods to better capture subtle autonomic changes [ 36 ]. Interestingly, the acute effect of tSCS at baseline had the opposite effect on HRV than the typically observed in SCI patients. Other neuromodulation strategies, such as transauricular Vagus Nerve Stimulation, have assessed vagal tone in individuals with SCI using RMSSD and HF power parameters. A significant increase in vagal tone was observed 24 hours after stimulation, compared with the sham group, in this population [ 37 ]. Therefore, we may interpret the increase in these values observed during the acute response following tSCS at 12 weeks as related to an increase in vagal tone. It remains to be determined whether the increase in vagal tone induced by tSCS also affects pain sensitivity, as observed in participants engaged in intense physical activity compared to those involved in more moderate forms of exercise [ 38 ]. As expected, the SI was the only parameter that showed the opposite behavior to the other time-domain parameters during pre-tSCS periods. This index reflects sympathetic predominance and is particularly relevant during orthostatic challenges [ 16 ]. However, in individuals with SCI, the restoration of sympatho-inhibition is impaired, which may exacerbate autonomic dysreflexia [39 Finally, the analysis of PNS and SNS indicators across the three pre-tSCS periods revealed a sustained increase in the SNS index up to 16 weeks, accompanied by a decrease in the PNS index. However, when examining the response between pre- and post-tSCS at baseline and 12 weeks, both indices tend to converge toward central values. This suggests a shift toward patterns observed in the restive values of the normative population, as proposed by the Kubios HRV developers’ User’s Guide [ 4 ]. These findings support the hypothesis that individuals with SCI may require alternative metrics distinct from normative standards, particularly regarding the predominance of sympatho-excitatory activity [ 40 ]. Although there is evidence supporting the beneficial effects of tSCS on autonomic dysreflexia [ 17 ], recent findings in two complete AIS-A subjects suggest that tSCS does not improve cardiovascular autonomic regulation, particularly at frequencies above 30 Hz with a 5 kHz carrier frequency [ 39 ]. Further studies are necessary to disclose the effects of tSCS on the ANS in large samples with varying levels of injury, as well as other clinical characteristics of the subjects (for example, time since injury, cause of injury, age of participants, etc.), to understand the cellular mechanisms by which benefits have been reported in subjects with SCI, while at the same time ruling out possible secondary harm to patients. In this sense, Soriano et al. (2025) described a neuronal circuit involved in autonomic dysreflexia using cutting-edge techniques in SCI animal models, which may be critical for improving neuromodulation strategies in the near future. Although Soriano et al. employed epidural stimulation [ 41 ], the principles described in their work could also benefit non-invasive neuromodulation strategies, such as those used in this study. Our study included six participants with complete injury and two with incomplete injury (AIS B and C). Similarly, six of the eight participants had thoracic injuries, and two had cervical injuries. The time since SCI ranged from 1.2 to 8 years. This variability is consistent with case series reported in the literature on tSCS [ 27 , 42 – 44 ]. However, an important difference in our study is that participants received two sessions per week, in contrast to intensive protocols that have primarily focused on motor outcomes [ 25 , 29 , 45 , 46 ]. Therefore, future studies may examine whether a more intensive tSCS + PT regimen could elicit more substantial changes than those observed in our intervention. Recently, Suggit et al. (2025) suggested that the benefits of tSCS, particularly motor function, become more evident after more than 60 sessions [ 30 ]. We acknowledge that our study has additional limitations, as previously reported in a meta-analysis aimed at elucidating the effect of tSCS on HRV parameters, including small sample size, high inter-individual variability in results, and the absence of a control group [ 47 ]. However, we observed the same sympathetic exacerbation of cardiac activity after 12 weeks, as previously described in the literature and attributed to various etiologies, such as loss of the descending inhibitory pathway, increased afferent sprouting and nerve growth factor, increased propriospinal neurons below the injury level, among others [ 48 ]. Taken together, our findings should be interpreted with caution, as the current literature on the effects of tSCS on objective indicators of autonomic function remains limited, consisting primarily of case reports and small case series. Moreover, variability in stimulation protocols (e.g., spinal level, number of electrodes, session frequency) and sample heterogeneity (e.g., complete vs. incomplete injuries, time since injury) further constrain the generalizability of results. Recently, Solinsky et al. (2025) proposed a battery of assessments to evaluate residual autonomic function in individuals with spinal cord injury, emphasizing the need for standardized testing tailored to this population, with HRV serving as a key reference metric [ 40 ]. 5. Conclusions Autonomic changes resulting from SCI are influenced by factors such as injury severity and level. tSCS is currently employed primarily to promote recovery of muscle tone and voluntary motor activity; however, it also exerts measurable effects on autonomic function. Our findings on improvements in autonomic function, despite variability among individuals, are in line with previous literature. Regarding HRV, studies have reported heterogeneous findings, most of which lack statistical significance. Nonetheless, these results support the hypothesis of a prevailing sympathetic tendency. To better understand the potential of plastic changes in cardiac modulation induced by tSCS, it is important to consider the timing between tSCS treatment and ECG recording. Our findings showed an increase in sympathetic activity, as reflected in both time-domain and frequency-domain HRV parameters when assessing long-term effects. In contrast, acute responses reveal a parasympathetic predominance immediately after the tSCS + PT session, following a 12-week therapy period (two sessions per week). This suggests that tSCS + PT may serve as a vagal tone enhancer in individuals with SCI. It is possible that, in this population, such modulation manifests as increased sympathetic activity, as evidenced by the improvements in other autonomic function indicators. However, this autonomic sympathetic/parasympathetic balance differs from that observed in able-bodied individuals, underscoring the need for SCI-specific metrics and interpretations. Abbreviations SCI Spinal Cord Injury PT Physical therapy BP Blood pressure ANS Autonomic Nervous System HRV Heart Rate Variability SA Sympathetic Autonomy PSA Parasympathetic Activity HF High frequency LF Low frequency ECG Electrocardiogram OH Orthostatic hypotension tSCS Transcutaneous Spinal Cord Stimulation tSCS+PT Transcutaneous Spinal Cord Stimulation and Physical Therapy ASAF Autonomic Assessment Standard Form NBSS Neurogenic Bladder Symptoms Score AIS American Spinal Cord Injury Association Impairment Scale HR Heart rate SCMEPS Spinal Cord Motor Evoked Potentials DBP Diastolic blood pressure SBP Systolic blood pressure ANOVA Analysis of Variance LT Light touch PP Pinprick Declarations Ethics approval and consent to participate: The study was conducted in accordance with the Declaration of Helsinki (2024) and approved by the Ethics Committee of the Faculty of Health Sciences of the Universidad Anáhuac México (protocol code 202209, approval date: May 31st, 2022). Informed consent was obtained from all subjects involved in the study . Clinical trial number: not applicable. Consent for publication: All study participants provided written informed consent prior to study enrollment and for the publication of their data. Data Availability Statement: The dataset supporting the conclusions of this article is available in the https://github.com/adriap3/Ingenier-a-en-Sistemas-Biom-dicos-FACMED/blob/fd96eac5845bb9a91f617a34a8c552a29d250024/Acute%20and%20Medium-Term%20Effects%20of%20Transcutaneous%20Spinal_p006-p010.zip Competing interest: The authors declare that they have no competing interests. Funding: This work was supported by the Universidad Anáhuac México through the Research Office. Author's contributions: APC, A, IL and C.AC. conceptualized the study. APC, DP, AM MG, ES, FR, and CAC participated in data acquisition. DP, AM, MG, ES, and FR, assisted with the physical therapy. APC, DP, AM, MG, ES, FR, and CAC participated in data curation., APC, AM, MG, ES, FR, and CAC, wrote and prepared the original draft. ACP, AI, and CAC; supervised the study. CAC has administered the study. AI and CAC, had a role for funding acquisition. All authors read and approved the final manuscript. Acknowledgments: We deeply thank the participants of our study and their caregivers. We recognize and underscore the substantial contributions of Omar Miranda-Ortega, Carim A. Ramírez-Sánchez, and Álvaro Rodríguez-Romero, for their role on the computational HRV data analysis. We also thank Frida Bailey, Pablo Latapí and Eduardo Monzalvo, Monserrat Martínez, Karla Jiménez, Lorermy Villalobos, and Aldo Chimal for their support during physical therapy sessions. Finally, we thank Dulce Vargas and Mariana Valdivieso for their support with administrative and logistical tasks during the conduct of this study. References Wang S, Chen S, Fan W, Chen T, Hu X, Li C, et al. 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Consequences of spinal cord injury on the sympathetic nervous system. Front Cell Neurosci. 2023;17:999253. Additional Declarations No competing interests reported. Supplementary Files Pliegoetal2025Supplementary.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 24 Feb, 2026 Reviews received at journal 02 Feb, 2026 Reviews received at journal 19 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers invited by journal 06 Jan, 2026 Editor assigned by journal 23 Dec, 2025 Submission checks completed at journal 23 Dec, 2025 First submitted to journal 18 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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1","display":"","copyAsset":false,"role":"figure","size":685913,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Flow chart of the protocol. (B). tSCS electrodes placement in paraplegia (T11-12, T12-L1) and tetraplegia (C5-6, C6-7). Cathodes, blue and orange circles; anodes, orange and blue rectangles. (C) ECG lead recording (ground, black circle; anode, gray circle; cathode, red circle.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/209a6c570eb68b6c135313c2.png"},{"id":100007594,"identity":"06fb3ce2-f82e-479a-a867-6f93f0076c50","added_by":"auto","created_at":"2026-01-12 05:50:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":216088,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTotal NBSS scores at baseline, 12, and 16 weeks (n=8).\u003c/strong\u003eNo significant differences (NS) were found when comparing total scores at baseline, 12, and 16 weeks (p\u0026gt;0.05, One Way ANOVA). Black and red lines in box graphs represent the median and mean, respectively.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/c0acc036bfa932491b4cd721.png"},{"id":100360901,"identity":"8c8d673c-9685-455f-aa0b-b247373b4656","added_by":"auto","created_at":"2026-01-16 07:44:09","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":307000,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAcute and midterm effect of tSCS+PT on mean MAP (mm Hg), HR (bpm), SpO2%, and body core temperature (°C) across time points (n=8).\u003c/strong\u003eNo significant differences were found in any parameter across 16 weeks (p\u0026gt;0.05, One Way ANOVA). NS, not statistically significant.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/7f20dbbcd8723c6e28f2a0aa.png"},{"id":100007602,"identity":"f0501b54-2fe9-44fa-8118-c6bcfe67491e","added_by":"auto","created_at":"2026-01-12 05:50:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":713543,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of tSCS+PT on HRV time-domain parameters (A-D), Ratio LF/HF, a frequency-domain parameter (E), and indexes SI (F), SND (G), and PNS (H).\u003c/strong\u003e Data were obtained pre- and post-SCS+PT at baseline, 12, and 16 weeks. No significant differences (p\u0026gt;0.05, One Way ANOVA) were found in any parameter between time points (NS). The black and red lines indicate the median and mean values, respectively.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/feaec07dc46e063d23467bfa.png"},{"id":100381328,"identity":"b3425af0-945f-405b-bfae-b9e09ff23ba8","added_by":"auto","created_at":"2026-01-16 10:38:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3309410,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/069dd9aa-ea6d-40c6-a739-fef3f4abf8f3.pdf"},{"id":100361120,"identity":"67bbee39-025d-4c16-8dea-22eccd11d05d","added_by":"auto","created_at":"2026-01-16 07:44:28","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":24019,"visible":true,"origin":"","legend":"","description":"","filename":"Pliegoetal2025Supplementary.docx","url":"https://assets-eu.researchsquare.com/files/rs-8398767/v1/ad706f528a6330bd968ac25f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Modulation of Autonomic Function and Heart Rate Variability by Transcutaneous Spinal Cord Stimulation and Physical Therapy in Individuals with Chronic Spinal Cord Injury","fulltext":[{"header":"1. Background","content":"\u003cp\u003eThe sequelae of spinal cord injury (SCI) compromise motor, sensory, and autonomic functions. Global data from 1990 to 2021 indicate an increase in the prevalence and incidence of this condition, and, since there is no clinical treatment that effectively reverses or mitigates post-SCI dysfunction, complications in the chronic stage of SCI result in high medical care costs and diminish patients' quality of life [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Furthermore, these complications can prevent the patient from undergoing physical therapy (PT) due to autonomic dysfunction symptoms, including orthostatic hypotension, sudden increase in blood pressure (BP) caused by peripheral stimulation, loss of sphincter control, inappropriate sweating, and altered thermoregulation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The evaluation of the autonomic nervous system (ANS) is not routinely or clinically exhaustively evaluated, posing a challenge for specialists due to the need for standardized assessment tools [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, heart rate variability (HRV) analysis, an indirect assessment of cardiac autonomic balance, provides insight into the relative predominance of sympathetic (SA) versus parasympathetic activation (PSA) influencing cardiac and vascular function. Time-domain and frequency-domain HRV parameters have been widely investigated and characterized for their association with sympathetic and parasympathetic branches of the autonomic nervous system in the regulation of cardiac function [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. For example, while a reduction in time-domain parameters (RMSSD, SDNN, and pNN50) suggests a predominance of sympathetic cardiac activity, an increase in high-frequency (HF) activity (0.15\u0026ndash;0.4 Hz), derived from the R-R interval power spectrum, from the QRS complex, is associated with parasympathetic modulation mediated by vagal activity [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePrevious evidence indicates that a decrease in HRV occurs within the 24 months following SCI [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In addition, differences in HRV parameters have been consistently reported in the literature for injured subjects compared to uninjured controls, showing that HRV is lower in individuals with SCI, as revealed by 24-hour Holter monitoring [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In addition, reductions in low-frequency (LF) and HF components have been reported in individuals with SCI compared to controls [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Similarly, Rodriguez et al. (2016) reported significantly lower LF and LF/HF ratios in paraplegia and tetraplegia than in able-bodied individuals during a fatigue test; on the other hand, HF did not show significant differences between groups [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. These results suggested the presence of cardiac autonomic dysfunction, particularly in tetraplegia, as reported by Malmqvist et al. (2015) in acute SCI [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe combination of postural maneuvers with electrocardiographic (ECG) recordings contributes to the study of cardiovascular autonomic responses in SCI, complementing evidence from resting HRV parameter analysis. For instance, Park et al. (2025) investigated the HRV in two groups of individuals with complete and incomplete SCI, categorized by the presence or absence of orthostatic hypotension (OH). They found that the OH group exhibited lower index values, such as RMSSD and SDNN, in the supine position, suggesting a reduced influence of cardiac PSA [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe evidence suggests that, in patients with SCI, the interplay between SA and PSA in cardiac modulation is impaired, depending on the complexity of the physical task. Particularly, the diminished sympathetic tone, evidenced by the high OH prevalence and generalized low mean BP values, could reflect a state of critical cardiovascular vulnerability. In addition, low values of HRV assessment appear similar to those observed in high-risk conditions such as myocardial infarction or sudden cardiac death [11\u0026ndash;13In addition, experts have suggested that metrics typically considered 'normal' in the general population do not apply directly to individuals with SCI [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] underscoring the need to develop parameters tailored to their condition.\u003c/p\u003e \u003cp\u003eTranscutaneous spinal cord stimulation (tSCS) is a non-invasive neuromodulation technique that delivers electrical current via electrodes placed on the skin. It has shown improvements in cardiovascular function by normalizing BP during the sit-up test [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] and mitigating autonomic dysreflexia [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In addition, tSCS benefits urinary [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] and anorectal functions [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough the results above show promise for improving autonomic function, the effects of tSCS combined with physical therapy (tSCS\u0026thinsp;+\u0026thinsp;PT) on HRV and on immediate and midterm cardiovascular sympathetic and parasympathetic parameters in individuals with SCI have not yet been described. In this study, our primary goal was to evaluate the effect of pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT on HRV at baseline, 12 weeks, and after suspending the intervention for 4 weeks to assess the persistence of effects (16 weeks). Secondarily, we aimed to evaluate changes in autonomic function using validated scales and physiological parameters.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003eThis study was a prospective, single-arm trial. The protocol was approved by the Research and Ethics Committees of Universidad An\u0026aacute;huac M\u0026eacute;xico (ID 202209, approval date: May 31, 2022). All procedures were conducted at the Movement Analysis Laboratory, Universidad An\u0026aacute;huac M\u0026eacute;xico. Individuals aged 18\u0026ndash;30 years of either sex were included if they were at least one year post-SCI and had an injury below the C3 level of any severity, as classified by AIS. Subjects were excluded if they presented with pressure ulcers, unresolved infections, unhealed or recent fractures, demyelinating processes, or any other condition that prevented participation in PT or exposure to electrical stimulation. Participants were excluded from the final analysis if they missed two consecutive sessions or more than four sessions in total.\u003c/p\u003e \u003cp\u003eEight male subjects with paraplegia (p004, p007, p008, p009, p010, and p011) and 2 subjects with tetraplegia (p012 and p013) were included in the study after providing informed consent. According to the AIS, six participants were classified as A, one as B, and one as C (Individual sensory and motor scores are included in Appendix B, Table B1, Individual baseline AIS scores). Six participants had thoracic injuries between T2 and T10, and two patients had cervical injuries. The median age of the subjects was 28.5 years (range 21\u0026ndash;50), and the median of years after SCI was 2.5. All SCIs were caused by trauma. The demographic and clinical characteristics of the participants are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eHeart rate (HR), BP, SpO2%, and core temperature (\u0026deg;C) were recorded at the beginning and end of each tSCS\u0026thinsp;+\u0026thinsp;PT session. The Autonomic Standard Assessment Form (ASAF) and the Neurogenic Bladder Symptom Score (NBSS) were applied at Baseline, 12, and 16 weeks as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA.\u003c/p\u003e \u003cp\u003etSCS was applied by two self-adhesive electrodes used as cathodes (2.5 cm diameter, Medstar) that were placed in the intervertebral spaces T11-12 and T12-L1 for subjects with paraplegia, and in C5-6 and C6-7 in subjects with quadriplegia, while two rectangular electrodes (4 x 8 cm, MedStar) used as anodes were placed on the iliac crests for subjects with paraplegia and over the middle third of the clavicles in subjects with quadriplegia (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). The stimulation current for each participant was determined based on spinal cord motor-evoked potentials (SCMEPs) recorded at baseline. Briefly, with the same electrode configuration described above, current pulses were applied at 0.2 Hz in 5 mA steps until SCMEPs were observed in at least one registered muscle. The muscles recorded bilaterally were the medial portion of the deltoid, biceps brachii, triceps brachii, and common flexor digitorum in the case of individuals with quadriplegia (n\u0026thinsp;=\u0026thinsp;2). For subjects with paraplegia (n\u0026thinsp;=\u0026thinsp;6), the muscles recorded were rectus femoris, biceps femoris, tibialis anterior, and lateral gastrocnemius. The signals were recorded at a sampling rate of 10 kHz (PowerLab, ADInstruments\u0026reg;) and visualized in real time within a 50-ms window. Finally, the current intensity corresponding to the SCMEP threshold of the first responsive muscle in each patient was reduced by 10%. This value was applied at 30 Hz (symmetrical biphasic pulses, 280 us per phase, DS8R Digitimer\u0026reg;) during tSCS\u0026thinsp;+\u0026thinsp;PT in both tetraplegia and paraplegia. Subjects received two tSCS\u0026thinsp;+\u0026thinsp;PT sessions per week for 12 weeks. The intervention was then suspended for 4 weeks, and subjects were reevaluated (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). Subjects with paraplegia underwent trunk control exercises in a sitting position on a Bobath table while subjects with tetraplegia performed arm and hand exercises in their wheelchairs (Appendix A). Exercises were performed according to each patient's capabilities and were supervised by a physical therapist. tSCS\u0026thinsp;+\u0026thinsp;PT sessions lasted 30\u0026ndash;40 minutes.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic and clinical characteristics of the participants.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient ID\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSex and age (years old)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAIS-grade\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNeurological level\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eYears post-SCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSCI cause\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTrauma from a falling weight directly onto the spine\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGunshot injury\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMotorcycle accident\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMotorcycle accident\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGunshot injury\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eT10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGunshot injury\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCar Accident\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale \u0026ndash; 26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGunshot injury\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAn Electrocardiogram (ECG) was recorded for 5 minutes in the 5th intercostal space along the midclavicular line corresponding to the V4 precordial lead with the subject lying in supine position (sampling frequency 1 kHz, ADInstruments\u0026reg;) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). ECG recordings were performed before (pre-tSCS\u0026thinsp;+\u0026thinsp;PT) and immediately after tSCS (post-tSCS\u0026thinsp;+\u0026thinsp;PT) at a) Baseline to assess acute effects; b) after 12 weeks of receiving tSCS\u0026thinsp;+\u0026thinsp;PT, to assess mid-term effects, and c) after 16 weeks (4 weeks after suspending the intervention to assess persistence of effects). Participants were requested to refrain from consuming caffeinated and alcoholic beverages at least 24 h prior to ECG recordings. The protocol timeline is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Data analysis\u003c/h2\u003e \u003cp\u003eBP, HR, SpO2% and core temperature (\u0026deg;C) were taken at the beginning and after each tSCS\u0026thinsp;+\u0026thinsp;PT session. Mean arterial pressure (MAP) was determined according to the formula: MAP\u0026thinsp;=\u0026thinsp;DBP + (1/3) * (SBP - DBP), where DBP is the diastolic blood pressure and SBP is the systolic blood pressure. The values corresponding to 4, 8, 12, and 16 weeks of the intervention were averaged to assess whether significant changes or trends occurred over time.\u003c/p\u003e \u003cp\u003eECG preprocessing began with a visual selection of a continuous 5-minute segment of the main recording to exclude motion artifacts. Subsequently, the Pan-Tompkins algorithm was applied in MATLAB to extract the R-R interval sequence. The latter was analyzed using Kubios HRV Scientific (Kubios, Finland) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], estimating the typical time-domain variables (Mean RR, SDNN, RMSSD, NN50, pNN50, RRTI, TINN), frequency-domain variables (VLF peak, LF peak, HF Peak, Total Power, and the LF/HF ratio), SI (Baevsky\u0026rsquo;s Stress Index), Parasympathetic Nervous System (PNS), and Sympathetic Nervous System (SNS) indexes for sympathetic/parasympathetic balance behavior in cardiac regulation. In patient p010, no baseline ECG recordings were obtained due to a residual scar at the ECG electrode placement site. After 3 months, scar healing allowed for the ECG recordings. Patient p009 did not return for the 16-week follow-up evaluations. Since only two subjects with tetraplegia were recruited, no comparisons were made between this group and the paraplegia group. The results for each variable were analyzed as a single group.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Statistical Analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics were obtained for quantitative variables. The ANOVA or Kruskal-Wallis test was used, depending on the data distribution, after applying the Shapiro-Wilk test. Next, the Equal Variance Test (Brown-Forsythe) was performed. If differences in the median or mean values were observed, a post-hoc analysis was carried out using Dunn's test with Bonferroni correction. The effect size for paired comparisons was calculated using Cohen\u0026rsquo;s d and the bias-corrected Hedges\u0026rsquo; g. Subsequently, 95% confidence intervals (CI 95%) were computed. Hedges\u0026rsquo; g values greater than 0.40 were considered to represent a large effect among the comparisons. Statistical tests and plots were performed in SigmaPlot 14.0 (SigmaStat).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Autonomic evaluations\u003c/h2\u003e \u003cp\u003eThe ASAF evaluations at baseline, 12, and 16 weeks are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In three subjects (p004, p007, and p008), the general and sacral autonomic sections remained unchanged at 16 weeks. Two participants (p009 and p011) increased by 1 pt. in the general autonomic section, while a decrease of 1 pt. occurred in p012. Four individuals (p009, p010, p012, and p013) showed an increase of at least 1 pt. in the sacral autonomic section; however, in p012, this increase was not sustained at 16 weeks. No significant differences were found when comparing the total score at baseline (median 11.0, P25-P75: 10.75-11.0), 12 (median 11.0, P25-P75: 10.75-11.0), and 16 (median 11.0, P25-P75: 10.75-11.0) weeks in the general autonomic function (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Similarly, no significant statistical differences were found when comparing the scores of sacral autonomic functions at baseline (median 3.5, P25-P75: 1.5-4.0), 12 (median 3.5, P25-P75: 2.5\u0026ndash;4.5), and 16 (median 3.5, P25-P75: 1.75\u0026ndash;5.25) weeks (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Regarding the Hedges\u0026rsquo; g values for the General Autonomic Section, these were \u0026lt;\u0026thinsp;0.4 in the comparisons of Baseline total scores vs. 12 weeks (g\u0026thinsp;=\u0026thinsp;0.34, CI 95% [-0.593, 1.273]) and Baseline vs. 16 weeks (g\u0026thinsp;=\u0026thinsp;0.0, CI 95% [-0.927, 0.927]). Similarly, when comparing the Hedges\u0026rsquo; g values for the total scores of the Sacral Autonomic Section, values\u0026thinsp;\u0026lt;\u0026thinsp;0.4 were found for Baseline vs. 12 weeks (g = -0.197, CI 95% [-1.126, 0.732]) and Baseline vs. 16 weeks (g = -2.05, CI 95% [-1.133, 0.723]). Individual ASAF scores are included in the Appendix B, Table B2, ASAF individual scores at baseline; Table B3, ASAF individual scores at 12 weeks, and Table B4, ASAF individual scores at 16 week.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eASAF scores at baseline, 12, and 16 weeks.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePatient ID\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eBaseline\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e12 weeks\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e16 weeks\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal Score General Autonomic Section\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal Score Sacral\u003c/p\u003e \u003cp\u003eAutonomic Section\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTotal Score General Autonomic Section\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal Score Sacral\u003c/p\u003e \u003cp\u003eAutonomic Section\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eTotal Score General\u003c/p\u003e \u003cp\u003eAutonomic Section\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eTotal Score\u003c/p\u003e \u003cp\u003eSacral\u003c/p\u003e \u003cp\u003eAutonomic\u003c/p\u003e \u003cp\u003eSection\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMedian P25\u003c/b\u003e,\u003c/p\u003e \u003cp\u003e\u003cb\u003eP75\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eSD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e10.75\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.88\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e1.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e4.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e2.32\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e10.75\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.46\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e3.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e2.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e4.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e2.32\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e10.75\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e11.0\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e0.64\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e3.5\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e1.75\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e5.25\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e2.44\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eASAF, Autonomic Standard Assessment Form.\u003c/p\u003e \u003cp\u003eThe results at baseline, 12, and 16 weeks of the total NBSS for each participant are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Regarding urinary function, three subjects (p007, p009, and p010) showed improvement in NBSS at 16 weeks compared to baseline. One participant (p004) improved considerably at 12 weeks, and then the score increased markedly in the final evaluation. In this case, the patient reported a urinary infection between 12 and 16 weeks, which likely contributed to the worsening of the NBSS. In one individual, the total NBSS remained unchanged (p013), and 3 subjects (p012, p008, and p011) worsened their scores at 16 weeks. Specifically, p008 and p012 used a permanent urinary catheter and reported urinary infections during the intervention. p011 had a stoma and reported greater scores at 12 weeks due to an increase in storing, combined with an increase in voiding sensation. No significant differences were found when comparing the total NBSS at baseline (median, 14.5; P25-P75: 9-29.5), 12 (median, 18.0, P25-P75: 10.0-26.75), and 16 weeks (median, 19.5; P25-P75:14.0-24.5) (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Hedges\u0026rsquo; g values for the NBSS resulted in no size effect in the comparisons of baseline total scores versus 12 weeks (g = -0.043, CI 95% [-0.970, 0.884]) and baseline versus 16 weeks (g =-0.08, CI 95% [-1.011, 0.843]). Individual NBSS scores are included in Appendix B, Table B5, NBSS individual scores at baseline, 12 and 16 weeks.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe MAP, HR, SpO2(%), and core temperature (\u0026deg;C) mean values across time points are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Data were obtained pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT at each session and averaged every 4 weeks to allow comparisons. MAP and HR (pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT) showed a slight tendency to increase after 4 weeks compared to baseline. In particular, the increase in HR was sustained through the final evaluation at 16 weeks (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). SpO2 (%) and body core temperature (\u0026deg;C) remained stable across all time points. No significant differences were found between pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT values at any time point for any parameter (MAP, HR, SpO2 (%), and core temperature), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Heart Rate Variability\u003c/h2\u003e \u003cp\u003eHRV time- and frequency-domain evaluations and corresponding indexes were performed pre-and post-tSCS\u0026thinsp;+\u0026thinsp;PT at baseline, 12, and 16 weeks (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). At baseline, the acute effect of tSCS\u0026thinsp;+\u0026thinsp;PT showed a slight increase in HRV in the post-tSCS\u0026thinsp;+\u0026thinsp;PT compared to pre-tSCS in all time-domain parameters (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-D, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Consistently, the SI showed a slight decrease, suggesting a decrease in sympathetic activity immediately after stimulation (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF). Interestingly, the midterm effect of pre-tSCS\u0026thinsp;+\u0026thinsp;PT after 12 weeks on HRV time-domain parameters decreased compared to baseline values, suggesting a consistent cardiac SA (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-D, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). However, the post-tSCS\u0026thinsp;+\u0026thinsp;PT effect on HRV at this point indicated a greater PSA predominance than pre-tSCS\u0026thinsp;+\u0026thinsp;PT. At 16 weeks, time-domain parameters (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-D, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and the SI index (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF) showed a tendency to revert to baseline values. The observed HRV pattern supports the hypothesis that alterations in HRV are primarily induced by the intervention (tSCS\u0026thinsp;+\u0026thinsp;PT), with transient effects dissipating after ceasing the intervention for 4 weeks.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhen analyzing the time-domain HRV parameters at the pre-tSCS\u0026thinsp;+\u0026thinsp;PT (Baseline) and pre-tSCS\u0026thinsp;+\u0026thinsp;PT (12 and 16 weeks) periods, the results suggest that, in the resting state, individuals with SCI generally exhibit an exacerbation of sympathetic cardiovascular modulation. This predominance appears to be further intensified following exposure to tSCS\u0026thinsp;+\u0026thinsp;PT, leading to increased regularity of heartbeats, as evidenced by a reduction in HRV dispersion at 12 weeks (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-D, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In our view, three events merit attention in time-domain HRV parameters: (1) during the pre-tSCS in the baseline and 12 weeks evaluation, a pronounced increase in HRV parameters is observed as a direct effect of tSCS\u0026thinsp;+\u0026thinsp;PT, suggesting plastic adaptations in autonomic regulatory pathways in response to tSCS exposure, particularly after the 12 weeks intervention; (2) in the mid-term response, following 12 weeks of continuous tSCS\u0026thinsp;+\u0026thinsp;PT, a reduction in the dispersion of beat-to-beat interval values is evident, indicating enhanced regularity in cardiac rhythm, particularly in the pre-tSCS-PT evaluation; and (3) after suspending the intervention for four weeks, HRV parameters tended to return to baseline levels, suggesting the transient nature of the intervention\u0026rsquo;s physiological effects. The pre-tSCS\u0026thinsp;+\u0026thinsp;PT effect analysis is particularly interesting, showing a change in the ratio percentage for the pNN50, a metric associated with cardiac parasympathetic influence, of 35.5% at Baseline, 160.3% at 12 weeks, and \u0026minus;\u0026thinsp;44% at 16 weeks, further supporting the notion that the observed effects are attributable to the tSCS\u0026thinsp;+\u0026thinsp;PT intervention (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBased on the duration of the ECG recordings, the frequency-domain analysis focused on parameters within the LF and HF bands. The peak values of the power spectrum with-in the LF and HF bands, associated with sympathetic and parasympathetic cardiovascular modulation, respectively, showed no changes in median values when comparing pre-tSCS\u0026thinsp;+\u0026thinsp;PT and post-tSCS\u0026thinsp;+\u0026thinsp;PT recordings at baseline, 12, and 16 weeks (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Consequently, no significant differences were found among time points (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The power of the LF and HF bands, which provide more comprehensive information on sympathetic and parasympathetic cardiac modulation respectively, exhibited a change ratio, shown as pre-tSCS\u0026thinsp;+\u0026thinsp;PT- post-tSCS\u0026thinsp;+\u0026thinsp;PT/pre-tSCS\u0026thinsp;+\u0026thinsp;PT of 0.229 at Baseline, 1.539 at 12 weeks, and 0.137 at 16 weeks for LF, and 0.248 at Baseline, 2.775 at 12 weeks, and \u0026minus;\u0026thinsp;0.239 at 16 weeks for HF. Consistent with the time-domain parameters, a more pronounced shift toward parasympathetic modulation was observed for the immediate response (pre vs. post-tSCS\u0026thinsp;+\u0026thinsp;PT) at 12 weeks, as reflected by the increase in HF power (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). However, the overall midterm effect of the intervention appears to suggest a slight enhancement in sympathetic predominance. This observation is further supported by the increase in the LF/HF ratio at 12 weeks compared to both Baseline and 16 weeks, indicating a shift towards sympathetic dominance following the intervention (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegarding the HRV indexes, the comparison of pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT values at baseline and after 12 weeks revealed a shift toward zero (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF-H and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), indicating a trend toward values observed in healthy individuals [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Interestingly, the comparison of pre-tSCS\u0026thinsp;+\u0026thinsp;PT values indicated a less parasympathetic (negative) and more sympathetic (positive) influence on heartbeat regulation, with this difference in cardiac autonomic predominance more pronounced at 12 weeks than at baseline or 16 weeks (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF-H and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). However, no significant differences were found when comparing SI, SNS, and PNS indexes at any time point in both pre-and post-tSCS\u0026thinsp;+\u0026thinsp;PT (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF-H and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHRV analysis: time- and frequency-domains, SI and PNS and SNS indexes in pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT at baseline, 12, and 16 weeks.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eBaseline\u003c/p\u003e \u003cp\u003eAcute effects\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e12 weeks\u003c/p\u003e \u003cp\u003eMidterm effects\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e16 weeks\u003c/p\u003e \u003cp\u003ePersistance of effects\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eTime-domain\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003cp\u003eP25\u003c/p\u003e \u003cp\u003eP75\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre-\u003c/p\u003e \u003cp\u003etSCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePost-\u003c/p\u003e \u003cp\u003etSCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePre-\u003c/p\u003e \u003cp\u003etSCS\u0026thinsp;+\u0026thinsp;PT\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePost-\u003c/p\u003e \u003cp\u003etSCS\u0026thinsp;+\u0026thinsp;PT\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePre-\u003c/p\u003e \u003cp\u003etSCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePost-\u003c/p\u003e \u003cp\u003etSCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMean RR\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e808.00\u003c/p\u003e \u003cp\u003e701.50 915.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e965.50\u003c/p\u003e \u003cp\u003e873.00 1383.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e827.00\u003c/p\u003e \u003cp\u003e683.00\u003c/p\u003e \u003cp\u003e867.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e836.00\u003c/p\u003e \u003cp\u003e745.00\u003c/p\u003e \u003cp\u003e890.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e830.00\u003c/p\u003e \u003cp\u003e756.00 954.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e823.5\u003c/p\u003e \u003cp\u003e753.00 943.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSDNN\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.00\u003c/p\u003e \u003cp\u003e18.35 48.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e41.05\u003c/p\u003e \u003cp\u003e20.62\u003c/p\u003e \u003cp\u003e56.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.4\u003c/p\u003e \u003cp\u003e19.7\u003c/p\u003e \u003cp\u003e31.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e38.20\u003c/p\u003e \u003cp\u003e30.50\u003c/p\u003e \u003cp\u003e48.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40.85\u003c/p\u003e \u003cp\u003e15.27\u003c/p\u003e \u003cp\u003e61.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e37.90\u003c/p\u003e \u003cp\u003e20.15\u003c/p\u003e \u003cp\u003e59.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNN50\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.00\u003c/p\u003e \u003cp\u003e0.75\u003c/p\u003e \u003cp\u003e112.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49.50\u003c/p\u003e \u003cp\u003e0.75\u003c/p\u003e \u003cp\u003e130.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.00\u003c/p\u003e \u003cp\u003e3.00\u003c/p\u003e \u003cp\u003e31.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32.00\u003c/p\u003e \u003cp\u003e28.00\u003c/p\u003e \u003cp\u003e73.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e61.50\u003c/p\u003e \u003cp\u003e0.00\u003c/p\u003e \u003cp\u003e107.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e33.50\u003c/p\u003e \u003cp\u003e0.00\u003c/p\u003e \u003cp\u003e117.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRMSSD\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33.00\u003c/p\u003e \u003cp\u003e10.92 55.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.40\u003c/p\u003e \u003cp\u003e13.52\u003c/p\u003e \u003cp\u003e66.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.20\u003c/p\u003e \u003cp\u003e17.30\u003c/p\u003e \u003cp\u003e29.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30.80\u003c/p\u003e \u003cp\u003e26.40\u003c/p\u003e \u003cp\u003e39.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e39.55\u003c/p\u003e \u003cp\u003e13.47\u003c/p\u003e \u003cp\u003e55.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e27.70\u003c/p\u003e \u003cp\u003e12.82\u003c/p\u003e \u003cp\u003e61.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003epNN50\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.18\u003c/p\u003e \u003cp\u003e0.15\u003c/p\u003e \u003cp\u003e37.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.52\u003c/p\u003e \u003cp\u003e0.21\u003c/p\u003e \u003cp\u003e45.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.20\u003c/p\u003e \u003cp\u003e0.69\u003c/p\u003e \u003cp\u003e8.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.33\u003c/p\u003e \u003cp\u003e7.16\u003c/p\u003e \u003cp\u003e19.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17.32\u003c/p\u003e \u003cp\u003e0.00\u003c/p\u003e \u003cp\u003e34.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9.61\u003c/p\u003e \u003cp\u003e0.00\u003c/p\u003e \u003cp\u003e36.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRR TI\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.99\u003c/p\u003e \u003cp\u003e6.82\u003c/p\u003e \u003cp\u003e11.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.44\u003c/p\u003e \u003cp\u003e7.71\u003c/p\u003e \u003cp\u003e12.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.62\u003c/p\u003e \u003cp\u003e4.66\u003c/p\u003e \u003cp\u003e9.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.21\u003c/p\u003e \u003cp\u003e8.04\u003c/p\u003e \u003cp\u003e12.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.12\u003c/p\u003e \u003cp\u003e7.61 13.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.22\u003c/p\u003e \u003cp\u003e6.23\u003c/p\u003e \u003cp\u003e15.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTINN\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(ms)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e184.5\u003c/p\u003e \u003cp\u003e91.00 233.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e205.50 101.25 277.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e157.00\u003c/p\u003e \u003cp\u003e98.00 178.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e198.00\u003c/p\u003e \u003cp\u003e140.00\u003c/p\u003e \u003cp\u003e251.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e199.50\u003c/p\u003e \u003cp\u003e76.75\u003c/p\u003e \u003cp\u003e274.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e190.50\u003c/p\u003e \u003cp\u003e98.50 297.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFrequency-domain\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLF peak\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003cp\u003e0.05\u003c/p\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003cp\u003e0.04\u003c/p\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHF peak\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003cp\u003e0.25\u003c/p\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003cp\u003e0.21\u003c/p\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003cp\u003e0.16\u003c/p\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003cp\u003e0.15\u003c/p\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003cp\u003e0.17\u003c/p\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003cp\u003e0.16\u003c/p\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLF power\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e732.5\u003c/p\u003e \u003cp\u003e315.25\u003c/p\u003e \u003cp\u003e1088.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e900.5\u003c/p\u003e \u003cp\u003e447.75\u003c/p\u003e \u003cp\u003e1122.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e245\u003c/p\u003e \u003cp\u003e182\u003c/p\u003e \u003cp\u003e477\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e622\u003c/p\u003e \u003cp\u003e469\u003c/p\u003e \u003cp\u003e1088.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e389.5\u003c/p\u003e \u003cp\u003e145.5\u003c/p\u003e \u003cp\u003e1385.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e443\u003c/p\u003e \u003cp\u003e250.5\u003c/p\u003e \u003cp\u003e1357\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHF power\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e523.5\u003c/p\u003e \u003cp\u003e77\u003c/p\u003e \u003cp\u003e1039.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e653.5\u003c/p\u003e \u003cp\u003e158\u003c/p\u003e \u003cp\u003e1441.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e111\u003c/p\u003e \u003cp\u003e74.5\u003c/p\u003e \u003cp\u003e250.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e419\u003c/p\u003e \u003cp\u003e242\u003c/p\u003e \u003cp\u003e652\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e480\u003c/p\u003e \u003cp\u003e189.5\u003c/p\u003e \u003cp\u003e1169.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e365.5\u003c/p\u003e \u003cp\u003e87.25\u003c/p\u003e \u003cp\u003e1357\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLF/HF\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.26\u003c/p\u003e \u003cp\u003e1.14\u003c/p\u003e \u003cp\u003e4.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.19\u003c/p\u003e \u003cp\u003e0.70\u003c/p\u003e \u003cp\u003e2.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.63\u003c/p\u003e \u003cp\u003e1.10\u003c/p\u003e \u003cp\u003e7.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.80\u003c/p\u003e \u003cp\u003e1.11\u003c/p\u003e \u003cp\u003e3.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.20\u003c/p\u003e \u003cp\u003e0.67\u003c/p\u003e \u003cp\u003e6.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.21\u003c/p\u003e \u003cp\u003e0.84\u003c/p\u003e \u003cp\u003e8.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIndexes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSI\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.80\u003c/p\u003e \u003cp\u003e8.07\u003c/p\u003e \u003cp\u003e22.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.00\u003c/p\u003e \u003cp\u003e6.97\u003c/p\u003e \u003cp\u003e19.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.50\u003c/p\u003e \u003cp\u003e12.50\u003c/p\u003e \u003cp\u003e21.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.00\u003c/p\u003e \u003cp\u003e7.90\u003c/p\u003e \u003cp\u003e14.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.80\u003c/p\u003e \u003cp\u003e7.30\u003c/p\u003e \u003cp\u003e26.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e13.40\u003c/p\u003e \u003cp\u003e7.20\u003c/p\u003e \u003cp\u003e19.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePNS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.77\u003c/p\u003e \u003cp\u003e-1.52\u003c/p\u003e \u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.22\u003c/p\u003e \u003cp\u003e-1.14\u003c/p\u003e \u003cp\u003e0.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-1.12\u003c/p\u003e \u003cp\u003e-1.69\u003c/p\u003e\u003cp\u003e-0.87\u003c/p\u003e\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.75,\u003c/p\u003e \u003cp\u003e-1.08\u003c/p\u003e \u003cp\u003e-0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.44\u003c/p\u003e \u003cp\u003e-1.28\u003c/p\u003e \u003cp\u003e0.26\u003c/p\u003e\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.95\u003c/p\u003e \u003cp\u003e-1.69\u003c/p\u003e \u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSNS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.94\u003c/p\u003e \u003cp\u003e-0.39\u003c/p\u003e \u003cp\u003e2.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003cp\u003e-0.67\u003c/p\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003cp\u003e0.96\u003c/p\u003e \u003cp\u003e3.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003cp\u003e0.19\u003c/p\u003e \u003cp\u003e1.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003cp\u003e-0.24\u003c/p\u003e \u003cp\u003e2.89\u003c/p\u003e\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003cp\u003e-0.19\u003c/p\u003e \u003cp\u003e2.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eHedges\u0026rsquo; g was calculated to estimate the effect size for pre- and post-tSCS\u0026thinsp;+\u0026thinsp;PT measures at baseline, 12 weeks, and 16 weeks for time- and frequency-domain HRV parameters. Only Hedges\u0026rsquo; g values\u0026thinsp;\u0026gt;\u0026thinsp;0.4 are reported next, across all possible pair-wise comparisons. For SDNN, a large effect was found at 12 weeks for pre- vs. post-tSCS\u0026thinsp;+\u0026thinsp;PT (g\u0026thinsp;=\u0026thinsp;1.64, CI 95% [0.30, 2.98]). Comparable findings were obtained for RMSSD at 12 weeks, pre-vs post-tSCS\u0026thinsp;+\u0026thinsp;PT (g\u0026thinsp;=\u0026thinsp;1.23, CI 95% [0.11, 2.42]). For the remaining parameters, high variability was observed; consequently, the mean differences were not statistically significant at the 95% confidence level.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eSCI is a complex condition that impairs motor and sensory functions below the lesion level, as well as autonomic functions involving the cardiovascular and bronchopulmonary systems, thermoregulation, sweating, sphincter control, and sexual function. Autonomic complications, such as orthostatic hypotension and autonomic dysreflexia, can limit the patient\u0026rsquo;s ability to engage in physical activity and rehabilitation, ultimately reducing quality of life and life expectancy [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In recent years, tSCS\u0026thinsp;+\u0026thinsp;PT has shown significant functional improvements following SCI. While most studies have focused on motor outcomes, fewer have addressed autonomic function, particularly cardiac autonomic modulation. The present study is the first to investigate both the baseline (acute) and mid-term (12 weeks) effects of tSCS\u0026thinsp;+\u0026thinsp;PT on HRV and autonomic function, as well as the persistence of these effects 4 weeks after the intervention ended (a total of 16 weeks) in individuals with paraplegia and tetraplegia. Importantly, HRV parameters were evaluated alongside validated measures of autonomic function, providing a novel and integrative contribution to understanding the overall impact of this therapeutic intervention.\u003c/p\u003e \u003cp\u003e Regarding autonomic outcomes, the most prominent improvements were observed in sacral autonomic function, particularly in gastrointestinal function and bladder filling sensation in three participants (p009, p010, and p013) (Appendix B, Tables B3, B4, and B5). For p009 and p010, these improvements were also reflected in reduced NBSS values (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Appendix B, Table B5). Importantly, p010 and p007 both achieved NBSS reductions of more than 5 points, representing a clinically significant change [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Although in this study we did not employ quantitative parameters of autonomic function, our results confirm previous findings that tSCS at 30 Hz benefits motor, sensory, and autonomic systems [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan additionalcitationids=\"CR26 CR27 CR28 CR29 CR30\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough no statistically significant differences were found between time points in the time-domain HRV indexes, tSCS\u0026thinsp;+\u0026thinsp;PT appears to have increased sympathetic influence on cardiac modulation when comparing pre-tSCS values at Baseline vs. 12 weeks, meaning that a potential decrease in parasympathetic cardiac modulation is reflected in the changes observed in RMSSD, NN50, and pNN50 at 12 weeks. After this period, a tendency to return toward Baseline values by 16 weeks was observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Serra-A\u0026ntilde;\u0026oacute; et al. (2015) reported that individuals with paraplegia exhibited lower time-domain HRV values than able-bodied controls; however, physical activity further reduced these values. Although current evidence remains inconclusive, it is hypothesized that, in paraplegia, a more pronounced sympathetic drive may represent a beneficial cardiovascular adaptation rather than an indicator of increased risk [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the frequency domain, previous evidence has shown significant differences in the LF band between individuals with SCI and able-bodied controls. In addition, the HF band exhibited greater variability, particularly between tetraplegic and paraplegic patients [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. In our study, we computed the power values for the LF and HF bands, representing the peak amplitude and the area under the curve. Baseline pre-tSCS\u0026thinsp;+\u0026thinsp;PT responses revealed a marked increase in both LF and HF power compared to post-tSCS\u0026thinsp;+\u0026thinsp;PT. This increase was also reflected in the LF/HF ratio, with the most notable change occurring at 12 weeks. In contrast, after 12 weeks, results showed a reduction in LF and HF power in both pre- and post-tSCS-PT, followed by a moderate elevation at 16 weeks (pre-tSCS\u0026thinsp;+\u0026thinsp;PT). Interestingly, our results resemble those obtained in SCI subjects after two sessions of 32 minutes of transcranial direct current stimulation, showing a significant increase in the LF/HF coefficient and a decrease in the HF band (33). The simultaneous power decrease at midterm and the acute increase in both bands suggest a joint enhancement of baroreflex and parasympathetic modulation. Again, as with time-domain parameters, frequency-domain results indicated increased sympathetic modulation. However, these frequency-domain findings may instead reflect a vagal tone reinforcement due to tSCS\u0026thinsp;+\u0026thinsp;PT. The increase in HRV observed when comparing pre-tSCS\u0026thinsp;+\u0026thinsp;PT to post-tSCS\u0026thinsp;+\u0026thinsp;PT at 12 weeks is similar to the increase in SDANN observed in 50 individuals with SCI over a 5-week period immediately after injury. The significant increase in this SDANN, measured using a Holter monitor, was interpreted as a compensatory cardiovascular response, modulated by a plastic changing system formed by the damaged axons aimed at restoring function [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe combination of physical exercises performed during PT sessions and tSCS has attracted significant interest, as evidenced by a recent protocol integrating tSCS with upper-limb exercise [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In this sense, we do not exclude the possibility that physical activity may have contributed to the changes observed in HRV parameters. Individuals with tetraplegia and paraplegia who exercised using a standing frame exhibited lower HR values and higher HF power, suggesting enhanced parasympathetic modulation associated with upright posture and active engagement [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Interestingly, with tSCS, the parasympathetic response appears to be stimulation frequency-dependent, as SDNN and pNN50 increased significantly in able-bodied volunteers with 45 Hz stimulation, while HF power decreased at 7 Hz [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Considering the above, further research is needed to determine whether interventions aimed at reinforcing vagal tone in SCI, such as physical exercise or targeted autonomic maneuvers, increase HRV or whether the observed changes predominantly reflect a shift toward sympathetic modulation. The lack of statistically significant differences in time-domain and frequency-domain parameters in our study may be attributed to the small sample size and/or the limited duration of the intervention. Considering the latter, 12 weeks of exposure to tSCS (two sessions per week) might not be sufficient to induce profound changes in cardiac autonomic modulation. Previous studies have emphasized that frequency-domain analysis may be low in sensitivity to short-term interventions and therefore recommend the use of nonlinear methods to better capture subtle autonomic changes [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInterestingly, the acute effect of tSCS at baseline had the opposite effect on HRV than the typically observed in SCI patients. Other neuromodulation strategies, such as transauricular Vagus Nerve Stimulation, have assessed vagal tone in individuals with SCI using RMSSD and HF power parameters. A significant increase in vagal tone was observed 24 hours after stimulation, compared with the sham group, in this population [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Therefore, we may interpret the increase in these values observed during the acute response following tSCS at 12 weeks as related to an increase in vagal tone. It remains to be determined whether the increase in vagal tone induced by tSCS also affects pain sensitivity, as observed in participants engaged in intense physical activity compared to those involved in more moderate forms of exercise [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. As expected, the SI was the only parameter that showed the opposite behavior to the other time-domain parameters during pre-tSCS periods. This index reflects sympathetic predominance and is particularly relevant during orthostatic challenges [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. However, in individuals with SCI, the restoration of sympatho-inhibition is impaired, which may exacerbate autonomic dysreflexia [39 Finally, the analysis of PNS and SNS indicators across the three pre-tSCS periods revealed a sustained increase in the SNS index up to 16 weeks, accompanied by a decrease in the PNS index. However, when examining the response between pre- and post-tSCS at baseline and 12 weeks, both indices tend to converge toward central values. This suggests a shift toward patterns observed in the restive values of the normative population, as proposed by the Kubios HRV developers\u0026rsquo; User\u0026rsquo;s Guide [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These findings support the hypothesis that individuals with SCI may require alternative metrics distinct from normative standards, particularly regarding the predominance of sympatho-excitatory activity [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Although there is evidence supporting the beneficial effects of tSCS on autonomic dysreflexia [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], recent findings in two complete AIS-A subjects suggest that tSCS does not improve cardiovascular autonomic regulation, particularly at frequencies above 30 Hz with a 5 kHz carrier frequency [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Further studies are necessary to disclose the effects of tSCS on the ANS in large samples with varying levels of injury, as well as other clinical characteristics of the subjects (for example, time since injury, cause of injury, age of participants, etc.), to understand the cellular mechanisms by which benefits have been reported in subjects with SCI, while at the same time ruling out possible secondary harm to patients. In this sense, Soriano et al. (2025) described a neuronal circuit involved in autonomic dysreflexia using cutting-edge techniques in SCI animal models, which may be critical for improving neuromodulation strategies in the near future. Although Soriano et al. employed epidural stimulation [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e], the principles described in their work could also benefit non-invasive neuromodulation strategies, such as those used in this study.\u003c/p\u003e \u003cp\u003eOur study included six participants with complete injury and two with incomplete injury (AIS B and C). Similarly, six of the eight participants had thoracic injuries, and two had cervical injuries. The time since SCI ranged from 1.2 to 8 years. This variability is consistent with case series reported in the literature on tSCS [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan additionalcitationids=\"CR43\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. However, an important difference in our study is that participants received two sessions per week, in contrast to intensive protocols that have primarily focused on motor outcomes [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Therefore, future studies may examine whether a more intensive tSCS\u0026thinsp;+\u0026thinsp;PT regimen could elicit more substantial changes than those observed in our intervention. Recently, Suggit et al. (2025) suggested that the benefits of tSCS, particularly motor function, become more evident after more than 60 sessions [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe acknowledge that our study has additional limitations, as previously reported in a meta-analysis aimed at elucidating the effect of tSCS on HRV parameters, including small sample size, high inter-individual variability in results, and the absence of a control group [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. However, we observed the same sympathetic exacerbation of cardiac activity after 12 weeks, as previously described in the literature and attributed to various etiologies, such as loss of the descending inhibitory pathway, increased afferent sprouting and nerve growth factor, increased propriospinal neurons below the injury level, among others [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Taken together, our findings should be interpreted with caution, as the current literature on the effects of tSCS on objective indicators of autonomic function remains limited, consisting primarily of case reports and small case series. Moreover, variability in stimulation protocols (e.g., spinal level, number of electrodes, session frequency) and sample heterogeneity (e.g., complete vs. incomplete injuries, time since injury) further constrain the generalizability of results. Recently, Solinsky et al. (2025) proposed a battery of assessments to evaluate residual autonomic function in individuals with spinal cord injury, emphasizing the need for standardized testing tailored to this population, with HRV serving as a key reference metric [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eAutonomic changes resulting from SCI are influenced by factors such as injury severity and level. tSCS is currently employed primarily to promote recovery of muscle tone and voluntary motor activity; however, it also exerts measurable effects on autonomic function. Our findings on improvements in autonomic function, despite variability among individuals, are in line with previous literature. Regarding HRV, studies have reported heterogeneous findings, most of which lack statistical significance. Nonetheless, these results support the hypothesis of a prevailing sympathetic tendency. To better understand the potential of plastic changes in cardiac modulation induced by tSCS, it is important to consider the timing between tSCS treatment and ECG recording. Our findings showed an increase in sympathetic activity, as reflected in both time-domain and frequency-domain HRV parameters when assessing long-term effects. In contrast, acute responses reveal a parasympathetic predominance immediately after the tSCS\u0026thinsp;+\u0026thinsp;PT session, following a 12-week therapy period (two sessions per week). This suggests that tSCS\u0026thinsp;+\u0026thinsp;PT may serve as a vagal tone enhancer in individuals with SCI. It is possible that, in this population, such modulation manifests as increased sympathetic activity, as evidenced by the improvements in other autonomic function indicators. However, this autonomic sympathetic/parasympathetic balance differs from that observed in able-bodied individuals, underscoring the need for SCI-specific metrics and interpretations.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"524\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eSCI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eSpinal Cord Injury\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003ePT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003ePhysical therapy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eBP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eBlood pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eANS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eAutonomic Nervous System\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eHRV\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eHeart Rate Variability\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eSA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eSympathetic Autonomy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003ePSA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eParasympathetic Activity\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eHF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eHigh frequency\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eLF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eLow frequency\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eECG\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eElectrocardiogram\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eOH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eOrthostatic hypotension\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003etSCS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eTranscutaneous Spinal Cord Stimulation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003etSCS+PT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eTranscutaneous Spinal Cord Stimulation and Physical Therapy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eASAF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eAutonomic Assessment Standard Form\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eNBSS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eNeurogenic Bladder Symptoms Score\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eAIS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eAmerican Spinal Cord Injury Association Impairment Scale\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eHR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eHeart rate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eSCMEPS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eSpinal Cord Motor Evoked Potentials\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eDBP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eDiastolic blood pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eSBP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eSystolic blood pressure\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eANOVA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eAnalysis of Variance\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003eLT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003eLight touch\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16.2214%;\"\u003e\n \u003cp\u003ePP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83.7786%;\"\u003e\n \u003cp\u003ePinprick\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate: The study was conducted in accordance with the Declaration of Helsinki (2024) and approved by the Ethics Committee of the Faculty of Health Sciences of the Universidad An\u0026aacute;huac M\u0026eacute;xico (protocol code 202209, approval date: May 31st, 2022). Informed consent was obtained from all subjects involved in the study\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u0026nbsp;\u003c/strong\u003enot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e All study participants provided written informed consent prior to study enrollment and for the publication of their data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement:\u0026nbsp;\u003c/strong\u003eThe dataset supporting the conclusions of this article is available in the https://github.com/adriap3/Ingenier-a-en-Sistemas-Biom-dicos-FACMED/blob/fd96eac5845bb9a91f617a34a8c552a29d250024/Acute%20and%20Medium-Term%20Effects%20of%20Transcutaneous%20Spinal_p006-p010.zip\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This work was supported by the Universidad An\u0026aacute;huac M\u0026eacute;xico through the Research Office.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026apos;s contributions:\u003c/strong\u003e APC, A, IL and C.AC. conceptualized the study. \u0026nbsp;APC, DP, AM MG, ES,\u0026nbsp;FR, and CAC participated in data acquisition. \u0026nbsp;DP, AM, MG, ES, and FR, assisted with the physical therapy. APC, DP, AM, MG, ES, FR, and CAC participated in data curation., APC, AM, MG, ES, FR, and CAC, wrote and prepared the original draft. ACP, AI, and CAC; supervised the study. CAC has administered the study. AI and CAC, had a role for funding acquisition. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e We deeply thank the participants of our study and their caregivers. We recognize and underscore the substantial contributions of Omar Miranda-Ortega, Carim A. Ram\u0026iacute;rez-S\u0026aacute;nchez, and \u0026Aacute;lvaro Rodr\u0026iacute;guez-Romero, for their role on the computational HRV data analysis. We also thank Frida Bailey, Pablo Latap\u0026iacute; and Eduardo Monzalvo, Monserrat Mart\u0026iacute;nez, Karla Jim\u0026eacute;nez, Lorermy Villalobos, and Aldo Chimal for their support during physical therapy sessions. Finally, we thank Dulce Vargas and Mariana Valdivieso for their support with administrative and logistical tasks during the conduct of this study.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWang S, Chen S, Fan W, Chen T, Hu X, Li C, et al. Global inequalities in the burden of traumatic spinal cord injury from 1990 to 2021: findings from the global burden of disease study 2021. Neuroepidemiology. 2025 Sept 25;1\u0026ndash;26.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGunduz H, Fidan Binak D. Autonomic dysreflexia: An important cardiovascular complication in spinal cord injury patients. Cardiol J. 2012;19(2):215\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYadav RL, Martin JC, Galea MP. Evaluation and management of autonomic functions in patients with spinal cord injury: A scoping review. 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Front Cell Neurosci. 2023;17:999253.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-medical-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejmr","sideBox":"Learn more about [European Journal of Medical Research](http://eurjmedres.biomedcentral.com)","snPcode":"40001","submissionUrl":"https://submission.nature.com/new-submission/40001/3","title":"European Journal of Medical Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"spinal cord injury, transcutaneous spinal cord stimulation, non-invasive neuromodulation, transspinal stimulation, autonomic function, physical therapy, heart rate variability, parasympathetic activity, sympathetic activity, tetraplegia, paraplegia","lastPublishedDoi":"10.21203/rs.3.rs-8398767/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8398767/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSpinal cord injury causes motor, sensory, and autonomic impairments. Transcutaneous spinal cord stimulation (tSCS) has shown potential to improve autonomic regulation, particularly cardiovascular and bladder control. Heart rate variability (HRV) serves as a non-invasive marker of autonomic balance, reflecting modulation of cardiac sympathetic and parasympathetic activity. The purpose of this study was to evaluate the effect of combined tSCS and physical therapy (tSCS + PT) on HRV and autonomic function metrics in chronic spinal cord injury.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEight participants (2 with tetraplegia, 6 with paraplegia) received tSCS at 30 Hz targeting T11–L1 or C5–T1, depending on injury level. Each underwent two tSCS + PT sessions per week for 12 weeks, followed by a 4-week washout period. Autonomic assessments included the Autonomic Standard Evaluation Form (ASAF), Neurologic Bladder Symptoms Score (NBSS), blood pressure, heart rate, SpO2%, and core temperature. Electrocardiograms were recorded pre- and post-tSCS + PT at baseline, 12, and 16 weeks.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBaseline effects of tSCS + PT revealed increased time-domain HRV parameters, suggesting enhanced cardiac parasympathetic activation (PSA). After 12 weeks, these parameters decreased, suggesting reduced cardiac PSA and enhanced sympathetic activation (SA). Similar results were found with frequency-domain parameters. Time-and frequency-domain parameters tended to return toward baseline after the 4-week therapy suspension. Two commonly reported HRV parameters, SDNN and RMSSD, showed large effects (g = 1.64, CI 95% [0.30, 2.98], and g = 1.23, CI 95% [0.11, 2.42], respectively) at 12 weeks when comparing pre- vs. post-tSCS + PT. Moderate, subject-related differences across evaluations were found in ASAF and NBSS (p \u0026gt; 0.05). Physiological metrics across time points did not show statistically significant differences (p \u0026gt; 0.05). Physiological metrics across time points did not show statistically significant differences (p \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCombined tSCS + PT elicited improvements in autonomic clinical measures, without statistically significant changes in time-domain or frequency-domain HRV parameters. Nonetheless, trends and size effect in SDNN and RMSSD suggested that tSCS + PT induced midterm SA and a transient PSA immediately post-tSCS + PT. The partial recovery of HRV after tSCS withdrawal indicates that the observed autonomic changes were therapy-related.\u003c/p\u003e","manuscriptTitle":"Modulation of Autonomic Function and Heart Rate Variability by Transcutaneous Spinal Cord Stimulation and Physical Therapy in Individuals with Chronic Spinal Cord Injury","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 05:50:22","doi":"10.21203/rs.3.rs-8398767/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-24T13:36:04+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-02T17:35:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-20T02:57:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"326609274218009834317222557245396740507","date":"2026-01-09T01:56:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"334806195770286656303554598637221624191","date":"2026-01-07T15:00:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T00:55:16+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-23T10:44:30+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-23T10:42:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Medical Research","date":"2025-12-18T20:28:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-medical-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejmr","sideBox":"Learn more about [European Journal of Medical Research](http://eurjmedres.biomedcentral.com)","snPcode":"40001","submissionUrl":"https://submission.nature.com/new-submission/40001/3","title":"European Journal of Medical Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b104772e-2e0f-4cb9-a797-1c42fa8c716f","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-30T12:38:35+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 05:50:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8398767","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8398767","identity":"rs-8398767","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}