Influence of body mass index and waist-to-height ratio on cardiac autonomic responses in young adult healthy men

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Araújo, Nilo M. Okuno, Julio C. Schamne This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6631247/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose The present study aimed to verify the influence of body mass index (BMI) and waist-to-height ratio (WHR) on rest and recovery cardiac autonomic control in young healthy adults. Methods Eighteen eutrophic individuals with WHR < 0.5 (G1) and thirteen obese individuals with WHR ≥ 0.5 (G2) took part in this study. All participants visit to the laboratory. Anthropometric (body mass, height, and waist circumference), body composition, blood pressure at rest, and resting heart rate variability (HRV) measures were initially performed. After this, the participants were submitted to an incremental test on a treadmill, followed by a period of recovery with an HRV record (300 s active recovery + 300 s passive recovery). Results The parasympathetic indexes of HRV (RMSSD and lnHF) were lower in G2 in comparison to G1 at rest (p < 0.05). During the recovery period, it was also observed in G2 lower values of RMSSD, lnHF, and HF (nu), but with higher values of LF (nu) and LF/HF (p < 0.05) when compared with G1. It was observed in G2 that lower RMSSD60 values were observed in some moments during active and passive recovery compared to G1 (p 0.05). Conclusion Thus, it was observed that obese individuals with WHR ≥ 0.5 presented a lower rest and recovery vagal activity and a higher recovery sympathetic activity, indicating a cardiac autonomic dysfunction. heart rate control young adults body mass index autonomic nervous system Figures Figure 1 Figure 2 Introduction Cardiac autonomic control can be evaluated using a heart rate (HR) monitor in stationary (rest) and non-stationary (post-exercise) conditions. The resting and post-exercise HR and HR variability (HRV) recordings provide useful information about the sympathetic and parasympathetic components of the autonomic nervous system [ 1 ]. Many studies have documented abnormal resting [ 2 , 3 ] and post-exercise [ 4 – 6 ] cardiac autonomic responses in individuals with a wide range of disease conditions. Impaired cardiac autonomic control is also observed in obese individuals [ 7 , 8 ]. The use of body mass index (BMI) to discriminate health status might be the main factor underlying these inconsistencies [ 8 ]. The amount of fat located in the central region of the body (i.e., visceral fat) has been shown to have a greater impact on cardiac autonomic activity than fat distributed throughout the body [ 9 – 11 ]. Thus, the waist-to-height ratio (WHR) may be a better anthropometric tool than BMI for discriminating health status in young people [ 12 ]. Studies demonstrated no difference in HRV at rest[ 13 ] and HRV recovery[ 14 , 15 ] in healthy young men compared with healthy obese young men. In these studies, the individuals were divided according to their BMI. Another study compared cardiac autonomic recovery in young men based on WHR [ 16 ]. An impaired cardiac autonomic recovery was demonstrated after maximal treadmill exercise in young men with high WHR, but with no significant group effect (lower vs. higher WHR) [ 16 ]. It is unknown whether the cardiac autonomic dysfunction in adult obese people is due to the amount of body fat per se or the associated chronic diseases (e.g., hypertension, type 2 diabetes) [ 13 , 14 ]. Moreover, the studies use only BMI or WHR to classify groups of healthy young men and healthy obese young men. Therefore, considering that waist circumference is strongly correlated to visceral obesity [ 17 ], maybe a relativized index (WHR) + BMI could be a good index to distinguish better the cardiac autonomic health status in young people. Thus, this study aimed to compare the response of various resting and post-exercise indexes of cardiac autonomic activity between eutrophic young men with low WHR and obese young men with high WHR. Methods Participants Thirty-one male individuals (19 to 34 years old) volunteered to participate in this study (Table 1 ). The subjects were recruited according to their body mass index (BMI) and waist-stature ratio (WSR) and then divided into two groups: G1 (n = 18), BMI 18.5 to 24.99 kg/m 2 and WSR < 0.5; G2 (n = 13), BMI ≥ 30 kg/m 2 and WSR ≥ 0.5. The exclusion criteria were: (a) the presence of any cardiovascular or metabolic disease, (b) articular or bone injury, (c) using any medication that could influence cardiovascular response, and (d) tobacco usage. All participants were aware of the procedures and risks of the experiment and signed an informed consent. The study was approved by the local Ethics Committee (number protocol approved 1.912.887) and performed following the ethical standards. All procedures were executed according to the 2013 Helsinki Declaration from the World Medical Association. The participants were instructed not to consume alcohol and caffeinated drinks and not to perform vigorous activities within 48 hours before the evaluations. Procedures All the participants visited the laboratory to collect data. Initially, an anamnesis was performed aiming to verify health history and the drugs used. After that, the procedures included anthropometric and body composition measurements, resting blood pressure, and heart rate variability (HRV) evaluation. Finally, they underwent a maximal incremental test on a treadmill followed by a recovery period. The height was determined on a stadiometer (Cardiomed, Curitiba, Brazil) with an accuracy of 0.1 cm, and the body mass was measured via a digital scale (Tanita, model UM-080, The Netherlands) with a precision of 0.1 kg. Using an inelastic tape measure, the waist circumference was verified at the middle point between the last ribs and the iliac crest [ 18 ]. The body composition (total fat and lean mass) was analyzed by tetrapolar bioimpedance analysis (Maltron, model BF906, UK) following pre-test instructions described by the manufacturer. The BMI and WSR were calculated via the following formulas: BMI = mass (kg) / height (m) 2 ; WSR = waist circumference (cm) / height (cm). The blood pressure was also measured through an automated blood pressure cuff (Omron HEM-631 INT, Digital BP monitor, Omron Healthcare, The Netherlands). While the subjects remained seated in a chair to perform the blood pressure measurement, the HRV was recorded continuously for 10 minutes through a portable HR monitor (Polar V800, Kempele, Finland) with a belt fastened around the participant’s chest. A schematic representation of the study protocol is presented in Fig. 1 . ************************** Fig. 1 ************************** Maximal Incremental Test The participants underwent a maximal incremental test (modified Bruce protocol) on a treadmill (Inbramed Millennium, model ATL, Porto Alegre, Brazil). The test started at 3.2 km.h − 1 with a constant slope of 0% and increments of 1.6 km.h − 1 every minute until the third minute. From the fourth minute, the speed remained constant, and the treadmill grade was increased (2% every minute) until voluntary exhaustion. The subjects performed an active recovery with a speed of 2.4 km.h − 1 and 2% of the slope during the first five minutes. The last five minutes of the recovery period were performed at rest in the seated position (passive recovery) [ 4 ]. Heart rate recovery assessment For assessing heart rate recovery (HRR) indices, the HR values at the time corresponding to recovery were initially calculated (HR = 60/R-R intervals). Then, the HRR indices were calculated: HR off-kinetics, ΔHR1, ΔHR2, and T30 10 − 40s . For the HR off-kinetics, it was considered the first 300 seconds of the HR values on the recovery onset period to calculate the fitting curve through the equation: HR (t ) = HR min + A off x exp [– (time – t )/ τ off ]. Where HR (t) represents the HR in corresponding time; HR min is the hypothetical HR level to which the computed exponential curve approaches asymptotically; A off is the amplitude of the HR response; t is the time of the recovery onset; and τ off is the time constant of the HR response [ 19 ]. The ΔHR1 and ΔHR2 were calculated as the difference between peak HR and the HR value at the first and second minute of recovery, respectively [ 4 ]. The T30 10 − 40s index was obtained by fitting the logarithm of HR (10th to 40th seconds of recovery) into a first-degree polynomial. The index is expressed as the negative reciprocal of the slope of the resulting line (-1 / slope) [ 1 , 5 ]. The first ten seconds were excluded from analyses because HR stabilizes at this time [ 1 ]. Heart rate variability The R-R intervals (RRi) were continuously recorded by a portable HR monitor (Polar V800, Kempele, Finland) at rest (before exercise), during, and after the maximal incremental treadmill test. The time and frequency domain indices of HRV were calculated using Kubios HRV software (version 3.1), considering the last 5 min window at rest and recovery. The ectopic beats were visually identified and manually excluded. The time domain indices analyzed were: RRi, SDNN (standard deviation of consecutive RRi), and RMSSD (root mean square successive differences between adjacent normal RRi). In the frequency domain, the high frequency (HF, 0.15–0.50 Hz) and low frequency (LF, 0.04–0.15 Hz) components were analyzed in both absolute and normalized units through Fast Fourier Transform (FFT). Additionally, the time-varying vagal-related index (RMSSD on subsequent 60 s non-overlapped segments – RMSSD 60s ) was calculated during active (5 min) and passive (5 min) recovery periods. Statistical Analyses The Shapiro-Wilk test was applied to check data distribution. The anthropometric characteristics between groups were compared with an unpaired sample Student t- test. Depending on the data distribution, the HRR indices, HRV indices, and RMSSD60s segments were compared through an unpaired sample Student t-test or Mann-Whitney. Moreover, Spearman correlations between anthropometric variables (BMI and WSR) and HRR (τ off , A off , HRmin, ΔHR1, ΔHR2, and T30 10 − 40s ) and HRV indices (RRi, SDNN, RMSSD, lnLF, lnHF, LF (nu), HF (nu), and LF/HF) were calculated for the entire group. Results Body mass, BMI, waist circumference, total body fat mass (kg), systolic and diastolic blood pressure were significantly higher (p < 0.05) in G2 compared to G1. Additionally, systolic and diastolic BP were significantly higher in G2 compared to G1 (Table 1 ). The total time to reach exhaustion during the incremental maximal test was lower in G2 (620 ± 151 s) compared to G1 (755 ± 122 s; p < 0.01). Table 1 Baseline subject characteristics. Group G1 (n = 18) G2 (n = 13) Age (years) 23.1 ± 4.1 24.8 ± 4.4 Height (m) 177.8 ± 5.1 175.8 ± 6.2 Body mass (kg) 71.1 ± 7.9 107.3 ± 7.4* Body mass index (kg/m 2 ) 22.4 ± 1.9 34.9 ± 3.7* Waist circumference (cm) 78.6 ± 6.5 107.6 ± 6.9* Waist-stature ratio 0.4 ± 0.1 0.6 ± 0.1* Total body fat mass (kg) 11.7 ± 4.3 43.9 ± 9.8* Total body lean mass (kg) 59.2 ± 5.1 63.7 ± 7.6 Systolic blood pressure (mmHg) 107.3 ± 12.7 118.5 ± 12.2* Diastolic blood pressure (mmHg) 66.3 ± 6.1 76.5 ± 12.1* * Significantly different from G1 (p < 0.05). ***************** [Table 1] ******************** The time and frequency domain indices of HRV are summarized in Table 2 . At rest, the RRi (ms), RMSSD (ms), and lnHF (ms 2 ) were significantly lower in G2 compared to G1 (p < 0.05). Furthermore, on post-exercise recovery, the RMSSD (ms), lnHF (ms 2 ), LF (nu), HF (nu), and LF/HF were all significantly different in G2 when compared to G1 (p < 0.05). Table 2 HRV indices at rest and after the maximal incremental test. Rest Recovery G1 G2 G1 G2 Time domain RRi (ms) 850.6 ± 96.2 757.7 ± 110.4* 561.1 ± 51.8 539.3 ± 38.2 SDNN (ms) 52.1 ± 12.5 40.4 ± 20.2 13.4 ± 6.4 9.5 ± 4.2 RMSSD (ms) 43.6 ± 13.9 30.9 ± 17.9* 7.6 ± 3.9 4.8 ± 1.9* Frequency domain lnLF (ms 2 ) 7.4 ± 0.7 6.6 ± 1.3 4.5 ± 1.1 4.1 ± 1.1 lnHF (ms 2 ) 6.4 ± 0.8 5.4 ± 1.4* 2.8 ± 1.3 1.9 ± 1.1* LF (nu) 70.3 ± 16.1 75.9 ± 12.3 83.5 ± 8.2 88.3 ± 7.2* HF (nu) 29.6 ± 15.9 24.1 ± 12.2 16.4 ± 8.2 11.6 ± 7.2* LF/HF 5.5 ± 6.1 7.1 ± 8.4 6.3 ± 2.9 10.6 ± 6.1* Values of mean ± SD. RRi = mean of normal R-R intervals; SDNN = standard deviation of normal RRi; RMSSD = root mean square of the successive differences between adjacent RRi; LF = low-frequency band; HF = high-frequency band. * Significantly different from G1 (p < 0.05). ***************** [Table 2 ] ******************** It was observed that significantly lower RMSSD 60s values in G2 in the third minute (p < 0.05) during active recovery (Fig. 2 a) and seventh, ninth, and tenth minutes (p < 0.05) during passive recovery (Fig. 2 b) when compared to G1. There was no significant difference in RMSSD 60s values between groups during the recovery period in the first, second, fourth, sixth, and eighth minutes (p > 0.05). ***************** [FIGURE 2 ] ******************** The HRR indices are summarized in Table 3 . It was observed that the amplitude (A off ) was significantly lower in G2 than in G1 (p 0.05). Table 3 HRR indices after incremental test. Group G1 G2 τ off (s) 105.9 ± 34.7 93.4 ± 33.4 HRmin (bpm) 116.9 ± 11.5 121.3 ± 7.4 A off (bpm) 65.6 ± 8.6 58.9 ± 9.1* ΔHR1 (bpm) 35.4 ± 6.9 32.4 ± 7.4 ΔHR2 (bpm) 52.5 ± 7.9 48.1 ± 8.5 T30 10 − 40s (s) 358.1 ± 169.7 384.8 ± 99.9 Values of mean ± SD. τoff = time constant of exponential curve; HRmin = value for the asymptotic portion of the curve; A off = amplitude of exponential curve; ΔHR1 = difference between peak HR at exercise and the HR value at the first minute of recovery; ΔHR2 = difference between peak HR at exercise and the HR value at the second minute of recovery; T30 10 − 40s = negative reciprocal of the slope obtained from a linear regression between natural logarithm transformed HR and the respective time. *Significantly different from G1 (p < 0.05). ***************** [Table 3 ] ******************** The correlations between anthropometric variables (BMI and WSR) with HRV and HRR indices are shown in Table 4 . The results demonstrated that BMI was inversely correlated with SDNN, RMSSD, LF, and HF indices. Meanwhile, BMI is inversely associated with RRi and RMSSD indices. Correlations between BMI and HRR parameters were not observed, but WSR was moderately correlated with HRmin and amplitude parameters. Table 4 Correlation between anthropometric variables and HRR and HRV indices. BMI WSR r p r p HRV indices RRi -0.32 0.08 -0.37* 0.04 SDNN -0.43* 0.02 -0.33 0.07 RMSSD -0.45* 0.01 -0.44* 0.01 LF -0.39* 0.03 -0.27 0.14 HF -0.40* 0.03 -0.31 0.09 LF/HF 0.24 0.20 0.24 0.20 HRR indices τ off 0.18 0.30 0.28 0.13 HRmin 0.33 0.07 0.47* 0.01 A off -0.21 0.26 -0.39* 0.03 ΔHR1 -0.31 0.91 -0.22 0.24 ΔHR2 -0.31 0.87 -0.27 0.14 T30 10s − 40s 0.21 0.25 0.19 0.30 RRi = mean of normal R-R intervals; SDNN = standard deviation of normal RRi intervals; RMSSD = root mean square of the successive differences between adjacent RRi; LF = low-frequency band; HF = high-frequency band; τoff = time constant of the exponential curve; HRmin = value for the asymptotic portion of the curve; A off = amplitude of exponential curve; ΔHR1 = difference between peak HR at exercise and the HR value at the first and minute of recovery; ΔHR2 = difference between peak HR at exercise and the HR value at the second and minute of recovery; T30 10 − 40s = negative reciprocal of the slope obtained from a linear regression between natural logarithm transformed HR and the respective time. * Significant correlation (p < 0.05). ******************** [Table 4 ] ******************** Discussion The main findings of the present study are that: (i) some parasympathetic indices were lower in obese young men at rest when compared with normal-weight young men; (ii) obese young men present changes in HRV RMSSD 60s at some moments after exercise recovery when compared with normal-weight young men; and (iii) obesity influences only the amplitude parameter of HR off-kinetics, but did not influence other HR off-kinetics and HRR parameters. Obesity associated with metabolic modifications may be associated with changes in cardiac autonomic modulation. These changes in cardiac autonomic modulation promote hyperactivity of the sympathetic nervous system and a reduction in the activity of the parasympathetic nervous system at rest [ 20 – 22 ]. Nonetheless, it is unclear whether obesity alone promotes these changes [ 13 , 14 ]. The present study verified that healthy obese young men had lower parasympathetic indices at rest compared to normal-weight young men. Thus, these results indicate that changes in cardiac autonomic modulation in adult obese people may result from the amount of body fat per se , but further studies are still needed to confirm and reinforce these findings. These results corroborate other studies that demonstrated changes in HRV indices in obese individuals compared to lean individuals [ 20 , 22 ]. However, these results did not corroborate with another study in which there was no difference in HRV indices at rest between healthy obese young men versus normal-weight young men [ 13 ]. A possible explanation for the differences found between the studies is classification criteria. The study of Araujo et al. [ 13 ] utilized only BMI, while this study used a relativized index of WHR + BMI. Post-exercise cardiac autonomic recovery is essential to verify the HR and HRV responses. After exercise, HR decreases due to a progressive reduction in metabolic activity. The HR recovery occurs exponentially, with a fast decay immediately after exercise (fast phase), which is determined predominantly by the parasympathetic reactivation, followed by a more gradual decay (slow phase), determined by the sympathetic withdrawal, until HR reaches its baseline values [ 1 ]. The present study observed differences in HRV indices (RMSSD, LF, HF, and LF/HF) and some moments of RMSSD 60s between healthy obese young men and normal-weight young men. These results demonstrated that parasympathetic parameters were lower and sympathetic parameters were higher in healthy obese young men when compared with normal-weight young men. This indicates a dysfunction in post-exercise cardiac autonomic recovery in obese young men. These results differ from previous studies that found no difference between healthy obese young men and normal-weight young men in HRV recovery [ 14 , 15 ]. Moreover, it corroborates with another study that demonstrated an impaired cardiac autonomic recovery after maximal treadmill exercise in young men with high WSR [ 16 ]. The classification criteria may have contributed to the difference in results. Some studies demonstrated that HRV is related to adiposity levels in healthy individuals [ 23 , 24 ]. The BMI may not provide accurate information for adiposity measurement [ 25 ]. It was suggested that abdominal obesity measured through WSR is more reliable than overall obesity quantified with BMI [ 26 ]. Thus, as used in this study, a relativized index (WHR + BMI) could be a better index to distinguish the cardiac autonomic health status in young men. Several indices have been proposed for HRR assessment, each derived through different methods [ 1 ]. Their physiological significance largely depends on the specific HRR phase being evaluated [ 1 ]. Some studies have shown that impaired HRR is associated with a higher BMI [ 27 ] and a higher percentage of body fat [ 28 ], indicating that obese individuals can exhibit cardiac autonomic modulation dysfunction. Unlike the articles cited above, we did not find significant associations between BMI and higher WRC with HRR indices. Some possible explanations for the differences are the age investigated, the exercise protocol, and the sample size used. This study's sample was much smaller than the previously cited studies. This study used different methods, such as HR off-kinetics, T30 10 − 40s, and decay of HR in the 30s (ΔHR 1 ) and 60s (ΔHR 2 ) after exercise. It was observed that only the amplitude parameter was different between obese young men when compared with normal-weight young men. These results are different from a previous study that showed a slower HRR after exercise in overweight/obese men when compared with the non-overweight/obese controls [ 29 ]. The exercise protocol was different between studies, which could explain these differences. The main limitation of the present study was that it did not measure other physiological parameters (i.e., HRV and HR on-kinetics). In addition, the lack of evaluation of HRR indices during submaximal exercises could provide further insights into the effects of obesity on HRR. Nevertheless, this study contributed to a better understanding of the impact of obesity on cardiac autonomic responses in young men. Further studies are required to investigate the effect of obesity at different intensities and with different exercise modalities. Conclusion In this study, obese individuals with WHR > 0.5 demonstrated impaired cardiac autonomic modulation, marked by reduced vagal activity both at rest and during recovery and elevated sympathetic activity during the recovery phase. These alterations suggest a potential predisposition to an increased risk of future cardiovascular complications. However, no significant differences were observed in heart rate recovery indices between obese (WHR > 0.5) and non-obese individuals (WHR < 0.5). Declarations Institutional review board statement This study and provided Resolution 466/2012 of the National Research Ethics Commission (CONEP) of the National Health Council and following the ethical principles of the Declaration of Helsinki (1964. revised in 2013) of the World Medical Association [2.3].The study was approved by the Research Ethics Committee of the State University of Ponta Grossa (number protocol approved 1.912.887). Ethical approval This study was conducted according to the Resolution 466/2012 of the National Research Ethics Commission (CONEP) of the National Health Council and following the ethical principles of the Declaration of Helsinki (1964revised in 2013) of the World Medical Association [2.3]. The study was approved by the Research Ethics Committee of the State University of Ponta Grossa (number protocol approved 1.912.887). Conflict of Interest Authors declare that they have no conflict of interest. Informed consent All participants voluntarily participated in this study and provided written informed consent. Author Contribution Conceptualization, A.C.A., A.FJ., J.C.S and N.M.O.; methodology, A.C.A., J.C.S and N.M.O.; data collection A.C.A. and N.M.O.; formal analysis, A.C.A., J.C.S and N.M.O.; writing—original draft preparation, A.FJ., J.C.S and N.M.O; writing—review and editing, all coauthors. All coauthors approved the submitted version. Acknowledgments We would like to thank the subjects for participating in this study and the Coordination for the Improvement of Higher Education Personnel (CAPES) for financial support. References Peçanha T, Bartels R, Brito LC, Paula-Ribeiro M, Oliveira RS, Goldberger JJ (2017) Methods of assessment of the post-exercise cardiac autonomic recovery: A methodological review. 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Arq Bras Cardiol 95:186–91. https://doi.org/10.1590/S0066-782X2010005000073 Barbosa Lins TC, Valente LM, Sobral Filho DC, Barbosa e Silva O (2015) Relação entre a frequência cardíaca de recuperação após teste ergométrico e índice de massa corpórea. Rev Port Cardiol 34:27–33. https://doi.org/10.1016/j.repc.2014.07.006 Silva CR da, Nascimento DC, Bicalho LCD, Tibana RA, Saraiva B, Willardson JM, et al (2017) Relationship between adiposity and heart rate recovery following an exercise stress test in obese older women. Braz J Kinathrop Hum Perform 19:554. https://doi.org/10.5007/1980-0037.2017v19n5p554 Dimkpa U, Godswill RC, Okonudo P, Ikwuka D (2023) Heart rate responses at rest, during exercise and after exercise periods in relation to adiposity levels among young nigerian adults. J Obes Metab Syndr 32:87–97. https://doi.org/10.7570/jomes22055 Additional Declarations No competing interests reported. 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Araújo","email":"","orcid":"","institution":"State University of Ponta Grossa","correspondingAuthor":false,"prefix":"","firstName":"Amanda","middleName":"C.","lastName":"Araújo","suffix":""},{"id":517273152,"identity":"781f08a6-48e3-4f5e-99a3-006f977d6cf3","order_by":2,"name":"Nilo M. Okuno","email":"","orcid":"","institution":"State University of Ponta Grossa","correspondingAuthor":false,"prefix":"","firstName":"Nilo","middleName":"M.","lastName":"Okuno","suffix":""},{"id":517273154,"identity":"26673cfc-ab57-4b6b-a8f8-397313faaa1e","order_by":3,"name":"Julio C. 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12:13:47","extension":"xml","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":102284,"visible":true,"origin":"","legend":"","description":"","filename":"2c5aed4956d24d458493db34aa75fe4e1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-6631247/v1/ce3a5caa5399da98702ddd82.xml"},{"id":91988490,"identity":"0f41da79-afa4-497f-b39b-5c318cbf7d4d","added_by":"auto","created_at":"2025-09-23 12:21:47","extension":"html","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":111610,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-6631247/v1/4ff4340334ebcfb496d359b1.html"},{"id":91988486,"identity":"8d8448c6-55bb-4aa0-ab24-641e47d545f3","added_by":"auto","created_at":"2025-09-23 12:21:47","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":117332,"visible":true,"origin":"","legend":"\u003cp\u003eProtocol of the study.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6631247/v1/ef0b6020f2269dae9e017a95.jpg"},{"id":91988124,"identity":"abd57b81-3133-4716-9081-b7d59588ae60","added_by":"auto","created_at":"2025-09-23 12:13:47","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":51064,"visible":true,"origin":"","legend":"\u003cp\u003eMean and SD of root-mean-square of successive differences in the RR intervals measured in successive 60s segments (RMSSD\u003csub\u003e60s\u003c/sub\u003e) during (a) 5 min active recovery and (b) 5 min passive recovery after the maximal incremental test for both G1 and G2 groups.\u003c/p\u003e\n\u003cp\u003e* Significantly different from G1 (p \u0026lt; 0.05).\u003c/p\u003e","description":"","filename":"OnlineFigure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6631247/v1/b8130effadf2a51524bf3e42.png"},{"id":96246290,"identity":"fd66251a-31f7-47d1-b8f6-a193d46504d6","added_by":"auto","created_at":"2025-11-19 07:25:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":873693,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6631247/v1/73691bff-5471-49d1-ba6a-f4835715168d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Influence of body mass index and waist-to-height ratio on cardiac autonomic responses in young adult healthy men","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCardiac autonomic control can be evaluated using a heart rate (HR) monitor in stationary (rest) and non-stationary (post-exercise) conditions. The resting and post-exercise HR and HR variability (HRV) recordings provide useful information about the sympathetic and parasympathetic components of the autonomic nervous system [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Many studies have documented abnormal resting [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and post-exercise [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] cardiac autonomic responses in individuals with a wide range of disease conditions. Impaired cardiac autonomic control is also observed in obese individuals [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe use of body mass index (BMI) to discriminate health status might be the main factor underlying these inconsistencies [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The amount of fat located in the central region of the body (i.e., visceral fat) has been shown to have a greater impact on cardiac autonomic activity than fat distributed throughout the body [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Thus, the waist-to-height ratio (WHR) may be a better anthropometric tool than BMI for discriminating health status in young people [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eStudies demonstrated no difference in HRV at rest[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] and HRV recovery[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] in healthy young men compared with healthy obese young men. In these studies, the individuals were divided according to their BMI. Another study compared cardiac autonomic recovery in young men based on WHR [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. An impaired cardiac autonomic recovery was demonstrated after maximal treadmill exercise in young men with high WHR, but with no significant group effect (lower vs. higher WHR) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIt is unknown whether the cardiac autonomic dysfunction in adult obese people is due to the amount of body fat \u003cem\u003eper se\u003c/em\u003e or the associated chronic diseases (e.g., hypertension, type 2 diabetes) [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Moreover, the studies use only BMI or WHR to classify groups of healthy young men and healthy obese young men. Therefore, considering that waist circumference is strongly correlated to visceral obesity [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], maybe a relativized index (WHR)\u0026thinsp;+\u0026thinsp;BMI could be a good index to distinguish better the cardiac autonomic health status in young people.\u003c/p\u003e\u003cp\u003eThus, this study aimed to compare the response of various resting and post-exercise indexes of cardiac autonomic activity between eutrophic young men with low WHR and obese young men with high WHR.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eParticipants\u003c/h2\u003e\u003cp\u003eThirty-one male individuals (19 to 34 years old) volunteered to participate in this study (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The subjects were recruited according to their body mass index (BMI) and waist-stature ratio (WSR) and then divided into two groups: G1 (n\u0026thinsp;=\u0026thinsp;18), BMI 18.5 to 24.99 kg/m\u003csup\u003e2\u003c/sup\u003e and WSR\u0026thinsp;\u0026lt;\u0026thinsp;0.5; G2 (n\u0026thinsp;=\u0026thinsp;13), BMI\u0026thinsp;\u0026ge;\u0026thinsp;30 kg/m\u003csup\u003e2\u003c/sup\u003e and WSR\u0026thinsp;\u0026ge;\u0026thinsp;0.5. The exclusion criteria were: (a) the presence of any cardiovascular or metabolic disease, (b) articular or bone injury, (c) using any medication that could influence cardiovascular response, and (d) tobacco usage. All participants were aware of the procedures and risks of the experiment and signed an informed consent. The study was approved by the local Ethics Committee (number protocol approved 1.912.887) and performed following the ethical standards. All procedures were executed according to the 2013 Helsinki Declaration from the World Medical Association. The participants were instructed not to consume alcohol and caffeinated drinks and not to perform vigorous activities within 48 hours before the evaluations.\u003c/p\u003e\n\u003ch3\u003eProcedures\u003c/h3\u003e\n\u003cp\u003eAll the participants visited the laboratory to collect data. Initially, an anamnesis was performed aiming to verify health history and the drugs used. After that, the procedures included anthropometric and body composition measurements, resting blood pressure, and heart rate variability (HRV) evaluation. Finally, they underwent a maximal incremental test on a treadmill followed by a recovery period.\u003c/p\u003e\u003cp\u003eThe height was determined on a stadiometer (Cardiomed, Curitiba, Brazil) with an accuracy of 0.1 cm, and the body mass was measured via a digital scale (Tanita, model UM-080, The Netherlands) with a precision of 0.1 kg. Using an inelastic tape measure, the waist circumference was verified at the middle point between the last ribs and the iliac crest [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The body composition (total fat and lean mass) was analyzed by tetrapolar bioimpedance analysis (Maltron, model BF906, UK) following pre-test instructions described by the manufacturer. The BMI and WSR were calculated via the following formulas: BMI\u0026thinsp;=\u0026thinsp;mass (kg) / height (m)\u003csup\u003e2\u003c/sup\u003e; WSR\u0026thinsp;=\u0026thinsp;waist circumference (cm) / height (cm).\u003c/p\u003e\u003cp\u003eThe blood pressure was also measured through an automated blood pressure cuff (Omron HEM-631 INT, Digital BP monitor, Omron Healthcare, The Netherlands). While the subjects remained seated in a chair to perform the blood pressure measurement, the HRV was recorded continuously for 10 minutes through a portable HR monitor (Polar V800, Kempele, Finland) with a belt fastened around the participant\u0026rsquo;s chest. A schematic representation of the study protocol is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e************************** Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e **************************\u003c/p\u003e\n\u003ch3\u003eMaximal Incremental Test\u003c/h3\u003e\n\u003cp\u003eThe participants underwent a maximal incremental test (modified Bruce protocol) on a treadmill (Inbramed Millennium, model ATL, Porto Alegre, Brazil). The test started at 3.2 km.h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a constant slope of 0% and increments of 1.6 km.h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e every minute until the third minute. From the fourth minute, the speed remained constant, and the treadmill grade was increased (2% every minute) until voluntary exhaustion. The subjects performed an active recovery with a speed of 2.4 km.h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2% of the slope during the first five minutes. The last five minutes of the recovery period were performed at rest in the seated position (passive recovery) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eHeart rate recovery assessment\u003c/h3\u003e\n\u003cp\u003eFor assessing heart rate recovery (HRR) indices, the HR values at the time corresponding to recovery were initially calculated (HR\u0026thinsp;=\u0026thinsp;60/R-R intervals). Then, the HRR indices were calculated: HR off-kinetics, ΔHR1, ΔHR2, and T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e.\u003c/p\u003e\u003cp\u003eFor the HR off-kinetics, it was considered the first 300 seconds of the HR values on the recovery onset period to calculate the fitting curve through the equation: \u003cem\u003eHR\u003c/em\u003e\u003csub\u003e\u003cem\u003e(t\u003c/em\u003e)\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eHR\u003c/em\u003e\u003csub\u003e\u003cem\u003emin\u003c/em\u003e\u003c/sub\u003e + \u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003eoff\u003c/em\u003e x\u003c/sub\u003e \u003cem\u003eexp\u003c/em\u003e [\u0026ndash; \u003cem\u003e(time\u003c/em\u003e \u0026ndash; \u003cem\u003et\u003c/em\u003e)/ \u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eoff\u003c/em\u003e\u003c/sub\u003e]. Where \u003cem\u003eHR\u003c/em\u003e\u003csub\u003e\u003cem\u003e(t)\u003c/em\u003e\u003c/sub\u003e represents the HR in corresponding time; \u003cem\u003eHR\u003c/em\u003e\u003csub\u003e\u003cem\u003emin\u003c/em\u003e\u003c/sub\u003e is the hypothetical HR level to which the computed exponential curve approaches asymptotically; \u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003eoff\u003c/em\u003e\u003c/sub\u003e is the amplitude of the HR response; \u003cem\u003et\u003c/em\u003e is the time of the recovery onset; and \u003cem\u003eτ\u003c/em\u003e\u003csub\u003e\u003cem\u003eoff\u003c/em\u003e\u003c/sub\u003e is the time constant of the HR response [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The ΔHR1 and ΔHR2 were calculated as the difference between peak HR and the HR value at the first and second minute of recovery, respectively [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e index was obtained by fitting the logarithm of HR (10th to 40th seconds of recovery) into a first-degree polynomial. The index is expressed as the negative reciprocal of the slope of the resulting line (-1 / slope) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The first ten seconds were excluded from analyses because HR stabilizes at this time [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eHeart rate variability\u003c/h3\u003e\n\u003cp\u003eThe R-R intervals (RRi) were continuously recorded by a portable HR monitor (Polar V800, Kempele, Finland) at rest (before exercise), during, and after the maximal incremental treadmill test. The time and frequency domain indices of HRV were calculated using Kubios HRV software (version 3.1), considering the last 5 min window at rest and recovery. The ectopic beats were visually identified and manually excluded.\u003c/p\u003e\u003cp\u003eThe time domain indices analyzed were: RRi, SDNN (standard deviation of consecutive RRi), and RMSSD (root mean square successive differences between adjacent normal RRi). In the frequency domain, the high frequency (HF, 0.15\u0026ndash;0.50 Hz) and low frequency (LF, 0.04\u0026ndash;0.15 Hz) components were analyzed in both absolute and normalized units through Fast Fourier Transform (FFT). Additionally, the time-varying vagal-related index (RMSSD on subsequent 60 s non-overlapped segments \u0026ndash; RMSSD\u003csub\u003e60s\u003c/sub\u003e) was calculated during active (5 min) and passive (5 min) recovery periods.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analyses\u003c/h2\u003e\u003cp\u003eThe Shapiro-Wilk test was applied to check data distribution. The anthropometric characteristics between groups were compared with an unpaired sample Student \u003cem\u003et-\u003c/em\u003etest. Depending on the data distribution, the HRR indices, HRV indices, and RMSSD60s segments were compared through an unpaired sample Student t-test or Mann-Whitney. Moreover, Spearman correlations between anthropometric variables (BMI and WSR) and HRR (τ\u003csub\u003eoff\u003c/sub\u003e, A\u003csub\u003eoff\u003c/sub\u003e, HRmin, ΔHR1, ΔHR2, and T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e) and HRV indices (RRi, SDNN, RMSSD, lnLF, lnHF, LF (nu), HF (nu), and LF/HF) were calculated for the entire group.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eBody mass, BMI, waist circumference, total body fat mass (kg), systolic and diastolic blood pressure were significantly higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) in G2 compared to G1. Additionally, systolic and diastolic BP were significantly higher in G2 compared to G1 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The total time to reach exhaustion during the incremental maximal test was lower in G2 (620\u0026thinsp;\u0026plusmn;\u0026thinsp;151 s) compared to G1 (755\u0026thinsp;\u0026plusmn;\u0026thinsp;122 s; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\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\u003eBaseline subject characteristics.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eG1 (n\u0026thinsp;=\u0026thinsp;18)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eG2 (n\u0026thinsp;=\u0026thinsp;13)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHeight (m)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e177.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e175.8\u0026thinsp;\u0026plusmn;\u0026thinsp;6.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody mass (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e71.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e107.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody mass index (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e22.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.9\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWaist circumference (cm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e78.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e107.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWaist-stature ratio\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal body fat mass (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal body lean mass (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e59.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e63.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSystolic blood pressure (mmHg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e107.3\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e118.5\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiastolic blood pressure (mmHg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e66.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e76.5\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003e* Significantly different from G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003e***************** [Table 1] ********************\u003c/h3\u003e\n\u003cp\u003eThe time and frequency domain indices of HRV are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. At rest, the RRi (ms), RMSSD (ms), and lnHF (ms\u003csup\u003e2\u003c/sup\u003e) were significantly lower in G2 compared to G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Furthermore, on post-exercise recovery, the RMSSD (ms), lnHF (ms\u003csup\u003e2\u003c/sup\u003e), LF (nu), HF (nu), and LF/HF were all significantly different in G2 when compared to G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\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\u003eHRV indices at rest and after the maximal incremental test.\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\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eRest\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eRecovery\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eG1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eG2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eG1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eG2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime domain\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRRi (ms)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e850.6\u0026thinsp;\u0026plusmn;\u0026thinsp;96.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e757.7\u0026thinsp;\u0026plusmn;\u0026thinsp;110.4*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e561.1\u0026thinsp;\u0026plusmn;\u0026thinsp;51.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e539.3\u0026thinsp;\u0026plusmn;\u0026thinsp;38.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSDNN (ms)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52.1\u0026thinsp;\u0026plusmn;\u0026thinsp;12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40.4\u0026thinsp;\u0026plusmn;\u0026thinsp;20.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e13.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e9.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRMSSD (ms)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43.6\u0026thinsp;\u0026plusmn;\u0026thinsp;13.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30.9\u0026thinsp;\u0026plusmn;\u0026thinsp;17.9*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFrequency domain\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003elnLF (ms\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003elnHF (ms\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLF (nu)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70.3\u0026thinsp;\u0026plusmn;\u0026thinsp;16.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e75.9\u0026thinsp;\u0026plusmn;\u0026thinsp;12.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e83.5\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e88.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHF (nu)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e29.6\u0026thinsp;\u0026plusmn;\u0026thinsp;15.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.1\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e16.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLF/HF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003eValues of mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. RRi\u0026thinsp;=\u0026thinsp;mean of normal R-R intervals; SDNN\u0026thinsp;=\u0026thinsp;standard deviation of normal RRi; RMSSD\u0026thinsp;=\u0026thinsp;root mean square of the successive differences between adjacent RRi; LF\u0026thinsp;=\u0026thinsp;low-frequency band; HF\u0026thinsp;=\u0026thinsp;high-frequency band.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e* Significantly different from G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e***************** [Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e] ********************\u003c/h2\u003e\u003cp\u003eIt was observed that significantly lower RMSSD\u003csub\u003e60s\u003c/sub\u003e values in G2 in the third minute (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) during active recovery (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) and seventh, ninth, and tenth minutes (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) during passive recovery (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) when compared to G1. There was no significant difference in RMSSD\u003csub\u003e60s\u003c/sub\u003e values between groups during the recovery period in the first, second, fourth, sixth, and eighth minutes (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e***************** [FIGURE \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e] ********************\u003c/h2\u003e\u003cp\u003eThe HRR indices are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. It was observed that the amplitude (A\u003csub\u003eoff\u003c/sub\u003e) was significantly lower in G2 than in G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The other HRR indices (τ\u003csub\u003eoff\u003c/sub\u003e, HRmin, ΔHR1, ΔHR2, and T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e) did not differ between G2 and G1 (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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\u003eHRR indices after incremental test.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eG1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eG2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eτ\u003csub\u003eoff\u003c/sub\u003e (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e105.9\u0026thinsp;\u0026plusmn;\u0026thinsp;34.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e93.4\u0026thinsp;\u0026plusmn;\u0026thinsp;33.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHRmin (bpm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e116.9\u0026thinsp;\u0026plusmn;\u0026thinsp;11.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e121.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003csub\u003eoff\u003c/sub\u003e (bpm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e65.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.1*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΔHR1 (bpm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΔHR2 (bpm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e52.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eT30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e358.1\u0026thinsp;\u0026plusmn;\u0026thinsp;169.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e384.8\u0026thinsp;\u0026plusmn;\u0026thinsp;99.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003eValues of mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. τoff\u0026thinsp;=\u0026thinsp;time constant of exponential curve; HRmin\u0026thinsp;=\u0026thinsp;value for the asymptotic portion of the curve; A\u003csub\u003eoff\u003c/sub\u003e = amplitude of exponential curve; ΔHR1\u0026thinsp;=\u0026thinsp;difference between peak HR at exercise and the HR value at the first minute of recovery; ΔHR2\u0026thinsp;=\u0026thinsp;difference between peak HR at exercise and the HR value at the second minute of recovery; T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e = negative reciprocal of the slope obtained from a linear regression between natural logarithm transformed HR and the respective time.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003e*Significantly different from G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e***************** [Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e] ********************\u003c/h2\u003e\u003cp\u003eThe correlations between anthropometric variables (BMI and WSR) with HRV and HRR indices are shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The results demonstrated that BMI was inversely correlated with SDNN, RMSSD, LF, and HF indices. Meanwhile, BMI is inversely associated with RRi and RMSSD indices. Correlations between BMI and HRR parameters were not observed, but WSR was moderately correlated with HRmin and amplitude parameters.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCorrelation between anthropometric variables and HRR and HRV indices.\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\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eBMI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eWSR\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003er\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003er\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHRV indices\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRRi\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.37*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.04\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSDNN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.43*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRMSSD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.45*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.44*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.39*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.40*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLF/HF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHRR indices\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eτ\u003csub\u003eoff\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHRmin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.47*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eA\u003csub\u003eoff\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.39*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΔHR1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΔHR2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eT30\u003csub\u003e10s\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003eRRi\u0026thinsp;=\u0026thinsp;mean of normal R-R intervals; SDNN\u0026thinsp;=\u0026thinsp;standard deviation of normal RRi intervals; RMSSD\u0026thinsp;=\u0026thinsp;root mean square of the successive differences between adjacent RRi; LF\u0026thinsp;=\u0026thinsp;low-frequency band; HF\u0026thinsp;=\u0026thinsp;high-frequency band; τoff\u0026thinsp;=\u0026thinsp;time constant of the exponential curve; HRmin\u0026thinsp;=\u0026thinsp;value for the asymptotic portion of the curve; A\u003csub\u003eoff\u003c/sub\u003e = amplitude of exponential curve; ΔHR1\u0026thinsp;=\u0026thinsp;difference between peak HR at exercise and the HR value at the first and minute of recovery; ΔHR2\u0026thinsp;=\u0026thinsp;difference between peak HR at exercise and the HR value at the second and minute of recovery; T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s\u003c/sub\u003e = negative reciprocal of the slope obtained from a linear regression between natural logarithm transformed HR and the respective time.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e* Significant correlation (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e******************** [Table \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e] ********************\u003c/h2\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe main findings of the present study are that: (i) some parasympathetic indices were lower in obese young men at rest when compared with normal-weight young men; (ii) obese young men present changes in HRV RMSSD\u003csub\u003e60s\u003c/sub\u003e at some moments after exercise recovery when compared with normal-weight young men; and (iii) obesity influences only the amplitude parameter of HR off-kinetics, but did not influence other HR off-kinetics and HRR parameters.\u003c/p\u003e\u003cp\u003eObesity associated with metabolic modifications may be associated with changes in cardiac autonomic modulation. These changes in cardiac autonomic modulation promote hyperactivity of the sympathetic nervous system and a reduction in the activity of the parasympathetic nervous system at rest [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Nonetheless, it is unclear whether obesity alone promotes these changes [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The present study verified that healthy obese young men had lower parasympathetic indices at rest compared to normal-weight young men. Thus, these results indicate that changes in cardiac autonomic modulation in adult obese people may result from the amount of body fat \u003cem\u003eper se\u003c/em\u003e, but further studies are still needed to confirm and reinforce these findings.\u003c/p\u003e\u003cp\u003eThese results corroborate other studies that demonstrated changes in HRV indices in obese individuals compared to lean individuals [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, these results did not corroborate with another study in which there was no difference in HRV indices at rest between healthy obese young men versus normal-weight young men [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. A possible explanation for the differences found between the studies is classification criteria. The study of Araujo et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] utilized only BMI, while this study used a relativized index of WHR\u0026thinsp;+\u0026thinsp;BMI.\u003c/p\u003e\u003cp\u003ePost-exercise cardiac autonomic recovery is essential to verify the HR and HRV responses. After exercise, HR decreases due to a progressive reduction in metabolic activity. The HR recovery occurs exponentially, with a fast decay immediately after exercise (fast phase), which is determined predominantly by the parasympathetic reactivation, followed by a more gradual decay (slow phase), determined by the sympathetic withdrawal, until HR reaches its baseline values [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The present study observed differences in HRV indices (RMSSD, LF, HF, and LF/HF) and some moments of RMSSD\u003csub\u003e60s\u003c/sub\u003e between healthy obese young men and normal-weight young men.\u003c/p\u003e\u003cp\u003eThese results demonstrated that parasympathetic parameters were lower and sympathetic parameters were higher in healthy obese young men when compared with normal-weight young men. This indicates a dysfunction in post-exercise cardiac autonomic recovery in obese young men. These results differ from previous studies that found no difference between healthy obese young men and normal-weight young men in HRV recovery [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Moreover, it corroborates with another study that demonstrated an impaired cardiac autonomic recovery after maximal treadmill exercise in young men with high WSR [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The classification criteria may have contributed to the difference in results. Some studies demonstrated that HRV is related to adiposity levels in healthy individuals [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The BMI may not provide accurate information for adiposity measurement [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. It was suggested that abdominal obesity measured through WSR is more reliable than overall obesity quantified with BMI [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Thus, as used in this study, a relativized index (WHR\u0026thinsp;+\u0026thinsp;BMI) could be a better index to distinguish the cardiac autonomic health status in young men.\u003c/p\u003e\u003cp\u003eSeveral indices have been proposed for HRR assessment, each derived through different methods [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Their physiological significance largely depends on the specific HRR phase being evaluated [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Some studies have shown that impaired HRR is associated with a higher BMI [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] and a higher percentage of body fat [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], indicating that obese individuals can exhibit cardiac autonomic modulation dysfunction. Unlike the articles cited above, we did not find significant associations between BMI and higher WRC with HRR indices. Some possible explanations for the differences are the age investigated, the exercise protocol, and the sample size used. This study's sample was much smaller than the previously cited studies.\u003c/p\u003e\u003cp\u003eThis study used different methods, such as HR off-kinetics, T30\u003csub\u003e10\u0026thinsp;\u0026minus;\u0026thinsp;40s,\u003c/sub\u003e and decay of HR in the 30s (ΔHR\u003csub\u003e1\u003c/sub\u003e) and 60s (ΔHR\u003csub\u003e2\u003c/sub\u003e) after exercise. It was observed that only the amplitude parameter was different between obese young men when compared with normal-weight young men. These results are different from a previous study that showed a slower HRR after exercise in overweight/obese men when compared with the non-overweight/obese controls [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The exercise protocol was different between studies, which could explain these differences. The main limitation of the present study was that it did not measure other physiological parameters (i.e., HRV and HR on-kinetics). In addition, the lack of evaluation of HRR indices during submaximal exercises could provide further insights into the effects of obesity on HRR. Nevertheless, this study contributed to a better understanding of the impact of obesity on cardiac autonomic responses in young men. Further studies are required to investigate the effect of obesity at different intensities and with different exercise modalities.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this study, obese individuals with WHR\u0026thinsp;\u0026gt;\u0026thinsp;0.5 demonstrated impaired cardiac autonomic modulation, marked by reduced vagal activity both at rest and during recovery and elevated sympathetic activity during the recovery phase. These alterations suggest a potential predisposition to an increased risk of future cardiovascular complications. However, no significant differences were observed in heart rate recovery indices between obese (WHR\u0026thinsp;\u0026gt;\u0026thinsp;0.5) and non-obese individuals (WHR\u0026thinsp;\u0026lt;\u0026thinsp;0.5).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eInstitutional review board statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study and provided Resolution 466/2012 of the National Research Ethics Commission (CONEP) of the National Health Council and following the ethical principles of the Declaration of Helsinki (1964. revised in 2013) of the World Medical Association [2.3].The study was approved by the Research Ethics Committee of the State University of Ponta Grossa (number protocol approved 1.912.887).\u0026nbsp;\u003c/p\u003e\u003ch2\u003eEthical approval\u003c/h2\u003e\u003cp\u003e This study was conducted according to the Resolution 466/2012 of the National Research Ethics Commission (CONEP) of the National Health Council and following the ethical principles of the Declaration of Helsinki (1964revised in 2013) of the World Medical Association [2.3]. The study was approved by the Research Ethics Committee of the State University of Ponta Grossa (number protocol approved 1.912.887).\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003cp\u003eAuthors declare that they have no conflict of interest.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eInformed consent\u003c/strong\u003e\u003cp\u003e All participants voluntarily participated in this study and provided written informed consent.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, A.C.A., A.FJ., J.C.S and N.M.O.; methodology, A.C.A., J.C.S and N.M.O.; data collection A.C.A. and N.M.O.; formal analysis, A.C.A., J.C.S and N.M.O.; writing\u0026mdash;original draft preparation, A.FJ., J.C.S and N.M.O; writing\u0026mdash;review and editing, all coauthors. All coauthors approved the submitted version.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e\u003cp\u003eWe would like to thank the subjects for participating in this study and the Coordination for the Improvement of Higher Education Personnel (CAPES) for financial support.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePe\u0026ccedil;anha T, Bartels R, Brito LC, Paula-Ribeiro M, Oliveira RS, Goldberger JJ (2017) Methods of assessment of the post-exercise cardiac autonomic recovery: A methodological review. 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J Obes Metab Syndr 32:87\u0026ndash;97. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.7570/jomes22055\u003c/span\u003e\u003cspan address=\"10.7570/jomes22055\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"heart rate control, young adults, body mass index, autonomic nervous system","lastPublishedDoi":"10.21203/rs.3.rs-6631247/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6631247/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003ePurpose\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe present study aimed to verify the influence of body mass index (BMI) and waist-to-height ratio (WHR) on rest and recovery cardiac autonomic control in young healthy adults.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e\u003cp\u003eEighteen eutrophic individuals with WHR\u0026thinsp;\u0026lt;\u0026thinsp;0.5 (G1) and thirteen obese individuals with WHR\u0026thinsp;\u0026ge;\u0026thinsp;0.5 (G2) took part in this study. All participants visit to the laboratory. Anthropometric (body mass, height, and waist circumference), body composition, blood pressure at rest, and resting heart rate variability (HRV) measures were initially performed. After this, the participants were submitted to an incremental test on a treadmill, followed by a period of recovery with an HRV record (300 s active recovery\u0026thinsp;+\u0026thinsp;300 s passive recovery).\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe parasympathetic indexes of HRV (RMSSD and lnHF) were lower in G2 in comparison to G1 at rest (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). During the recovery period, it was also observed in G2 lower values of RMSSD, lnHF, and HF (nu), but with higher values of LF (nu) and LF/HF (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) when compared with G1. It was observed in G2 that lower RMSSD60 values were observed in some moments during active and passive recovery compared to G1 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The other heart rate recovery indices did not differ between G2 and G1 (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThus, it was observed that obese individuals with WHR\u0026thinsp;\u0026ge;\u0026thinsp;0.5 presented a lower rest and recovery vagal activity and a higher recovery sympathetic activity, indicating a cardiac autonomic dysfunction.\u003c/p\u003e","manuscriptTitle":"Influence of body mass index and waist-to-height ratio on cardiac autonomic responses in young adult healthy men","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-23 12:13:42","doi":"10.21203/rs.3.rs-6631247/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f794f357-f63d-4033-8a7a-7434e4c01f7f","owner":[],"postedDate":"September 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-15T07:53:56+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-23 12:13:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6631247","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6631247","identity":"rs-6631247","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}