Influence of deep neck flexor activation on transversus abdominis and internal oblique recruitment during abdominal drawing-in maneuver: An ultrasound imaging study

Influence of deep neck flexor activation on transversus abdominis and internal oblique recruitment during abdominal drawing-in maneuver: An ultrasound imaging study | 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 Influence of deep neck flexor activation on transversus abdominis and internal oblique recruitment during abdominal drawing-in maneuver: An ultrasound imaging study Banu Gokcen BAYDOGAN TAN, Sefa TAN, Belgin KARAOGLAN This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6623126/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 Background/aim: Muscle activity in one region of the human body can influence muscle function in other regions, particularly between the cervical and lumbopelvic regions. The deep neck flexors (DNF) play a critical role in cervical spine stability and may have neuromuscular connections with deep core muscles. However, the impact of DNF activation on the transversus abdominis (TrA) and internal oblique (IO) muscles during the abdominal drawing-in maneuver (ADIM) remains unexplored. This study aimed to investigate the influence of DNF activation on TrA and IO muscle activity during the ADIM using ultrasound imaging (USI) to assess changes in muscle thickness and contraction ratio (CR). Materials and methods: Twentyseven healthy male participants (mean age: 34.24 ± 5.1 years, BMI: 23.66 ± 2.8 kg/m²) were recruited. Muscle thickness of the TrA and IO was measured at rest, during the ADIM, and during the ADIM with DNF activation. Contraction ratio (CR) was calculated as: CR = thickness during ADIM (with or without DNF activation) / resting thickness to assess relative changes in muscle activity. A paired t-test was used to compare muscle thickness and CR across conditions. Results: No significant changes were observed in TrA and IO muscle thickness with DNF activation (p > 0.05). However, a significant increase in TrA CR was observed bilaterally during DNF activation (right: t = 2.24, p = 0.03, Cohen’s d = 0.50; left: t = 2.04, p = 0.04, Cohen’s d = 0.50), while IO CR remained unchanged. Conclusion: The findings suggest that DNF activation selectively enhances TrA recruitment during the ADIM without affecting IO activation. This supports the hypothesis of neuromuscular interactions between the cervical and lumbopelvic regions, possibly mediated by myofascial and proprioceptive connections. Integrating DNF activation into core stabilization exercises may optimize deep core engagement, improve postural stability, and enhance neuromuscular control. Future research should investigate the long-term functional implications and include a broader participant demographic. transversus abdominis abdominal drawing-in maneuver deep neck flexor ultrasound imaging Figures Figure 1 1. Background Muscle activity in one region of the human body can significantly influence muscle function in other regions, contributing to overall postural stability during movement. The body's musculoskeletal system operates as an interconnected network where forces and activations are distributed across multiple segments particularly evident between the head and neck regions and the lumbopelvic region to maintain balance and efficient motion ( 1 ). The primary role of the cervical spine is to support the head against gravitational forces while facilitating multidirectional movement. In addition, the cervical spine features an exquisitely sensitive proprioceptive system that conveys the spatial orientation of the head relative to the torso, integrates signals from both the vestibular and ocular systems, and is fundamental to sustaining full-body postural control and balance ( 2 ). To fulfill these functions, the cervical spine must maintain robust mechanical stability in both static and dynamic positions ( 3 ). This stabilization is facilitated by the coordinated activity of the extensor and flexor muscles surrounding the cervical spine. Among these, the deep cervical flexors , including the longus capitis and longus colli , play a crucial role in controlling and supporting cervical lordosis , thereby ensuring the maintenance of optimal postural alignment of the cervical spine. These deep segmental muscles contribute to cervical spine stability by providing fine motor control and proprioceptive feedback , which are essential for postural adjustments and movement precision ( 4 , 5 ). Similarly, the abdominal muscles, including the Internal Oblique (IO), and Transversus Abdominis (TrA), play a vital role in core stability by facilitating trunk movement, protecting visceral structures, and distributing mechanical loads ( 6 , 7 ). As the deepest of the abdominal muscles, the TrA functions as a key stabilizer of the spine and pelvis , providing foundational support before any limb movement occurs ( 8 ). Its primary function is to increase intra-abdominal pressure , which enhances spinal rigidity and reduces excessive strain on the vertebral column ( 9 ). This stabilization is essential for maintaining proper posture, particularly during dynamic activities such as walking, lifting, and reaching ( 10 ). Core stabilization exercises such as the abdominal drawing-in maneuver (ADIM), bridging, curl-ups, abdominal stretching, and maximal exhalation have been shown to effectively engage these muscles ( 11 ). To facilitate the activation of the TrA , the ADIM , which is a common component of lumbar stabilization exercise programs, is particularly recommended ( 11 , 12 ). A previous study has demonstrated that the ADIM is more effective in facilitating TrA activation compared to other superficial muscles ( 8 ). Additionally, the ADIM increases the activity of the IO muscles ( 7 , 9 ), leading to a co-contraction of the Multifidus muscles ( 10 ), which, in turn, contributes to enhanced trunk stability . Ultrasound imaging (USI) has been widely employed in clinical settings for several years to quantify changes in abdominal muscle thickness and muscle activation patterns , providing a non-invasive and reliable method for evaluating motor control adaptations following core stabilization exercises ( 13 ). Previous research has demonstrated that USI is an effective tool for detecting changes in TrA and IO muscle thickness and activation during the ADIM ( 14 ). Moreover, its validity has been established through comparisons with electromyography (EMG) ( 15 ) and magnetic resonance imaging (MRI) ( 16 ), confirming its accuracy in measuring deep muscle function. Additionally, USI has been shown to have high interobserver reliability in both healthy individuals and patients with low back pain (LBP) ( 17 ), making it a valuable instrument. Emerging evidence suggests that there are anatomical and functional connections between the cervical and lumbar regions via fascial continuities (e.g., thoracolumbar fascia, deep front line), shared central motor pathways, and proprioceptive integration mechanisms. These interconnections raise the possibility that activation of stabilizing cervical muscles, such as the DNFs, may enhance or modulate the recruitment of abdominal core muscles, particularly the TrA. While previous studies have reported that core exercises combined with lower limb movement ( 18 ), maximal expiration ( 19 ), and simulated weight-bearing ( 20 ) enhance abdominal muscle co-contraction , leading to greater activation of the deep core muscles, the impact of the deep neck flexor (DNF) on the activation of TrA and IO remains unexamined. Given the crucial role of the DNF muscles in cervical spine stability ( 5 ) and their potential neuromuscular connections with the trunk , it is hypothesized that DNF activation influences the recruitment patterns of the IO and TrA muscles during the ADIM . The aim of this study is to investigate the influence of DNF activation on the recruitment patterns of the IO and TrA muscles during the ADIM . By utilizing USI , this study seeks to quantify changes in muscle thickness and activation to determine whether DNF activation enhances deep abdominal muscle engagement . The findings may contribute to a better understanding of neuromuscular interactions between the cervical and lumbopelvic regions , providing insights for core stabilization training and rehabilitation strategies aimed at improving postural control and musculoskeletal function . 2. Materials & Methods 2.1. Participants An a priori power analysis based on a previous study ( 1 ) indicated that 27 participants would be required to detect a moderate effect size (ES = 0.5) with an alpha of 0.05 and 80% power. Accordingly, 27 healthy male volunteers aged 18–45 years were recruited for this cross-sectional study. Inclusion criteria included the absence of neck or back pain, and the cognitive ability to understand and perform the study procedures. Exclusion criteria included a history of trauma or surgery involving the cervical, thoracic, lumbar, or abdominopelvic regions in the past year, presence of kyphoscoliosis (clinically or radiographically), or systemic diseases affecting the musculoskeletal or nervous systems (e.g., Parkinson’s disease, multiple sclerosis, malignancy, stroke). Participants were recruited voluntarily from hospital staff. They were informed verbally and in writing, and signed informed consent forms. The study adhered to the Declaration of Helsinki and Good Clinical Practice principles and received approval from the Gazi University School of Medicine Ethics Committee (Approval No: 23, Date: 23.11.2023). 2.2. Equipment and Ultrasonographic Assessment USI was performed using a MyLab 70 XV system (Esaote Biomedica, Genoa, Italy) with a 5–12 MHz linear probe and standard ultrasound gel. Bilateral measurements of the TrA and IO muscles were obtained in supine position, following established protocols ( 21 ).The probe was placed transversely, 25 mm anteromedial to the midpoint between the anterior axillary line, iliac crest, and 12th rib. Muscle thickness was measured as the perpendicular distance between hyperechoic fascial borders ( 22 ) (Figure). Each measurement was performed three times, and the mean value was recorded. Contraction ratio (CR) was calculated as: CR = thickness during ADIM (with or without DNF activation) / resting thickness ( 23 ). To ensure reliability, the order of measurements was randomized. All assessments were conducted by the same experienced physiatrist, and repeated on the same day to evaluate intra-rater reliability. 2.3. Procedures: Three experimental conditions were assessed: Resting state / ADIM alone / ADIM with DNF activation 2.3.1. ADIM ADIM was performed based on Richardson et al.'s protocol ( 24 ). Participants lay in a crook-lying position (hips 40–60° flexed, knees 90–100° flexed), arms resting by the sides. They were instructed to gently draw the navel toward the spine without moving the pelvis or rib cage. Proper contraction was confirmed by palpation medial to the anterior superior iliac spine, characterized by a slow, deep tension in the abdominal wall held for 10 seconds. This clinical palpation method, though widely used, has limitations due to its subjective nature and reliance on practitioner experience. 2.3.2. DNF DNF activation was performed using the craniocervical flexion test (CCFT), per the protocol of Jull et al. ( 25 ). Participants performed a nodding motion while lying supine, progressively increasing pressure from 20 mmHg to 24 mmHg on a pressure biofeedback unit (Chattanooga Stabilizer, DJO LLC, USA) placed suboccipitally ( 26 ). Visual feedback was provided. Participants were trained to minimize superficial muscle involvement and maintain 24 mmHg for the duration of the contraction. 2.4. Data Analysis: All statistical analyses were performed using SPSS 22.0 (IBM Corp., Armonk, NY). Normality of the data was assessed using the Shapiro–Wilk test. For normally distributed variables, a paired t-test was used to compare muscle thickness and contraction ratios between the ADIM alone and ADIM with DNF conditions. Effect sizes were calculated using Cohen’s d with 95% confidence intervals (CIs), and interpreted as small (≥ 0.20), moderate (≥ 0.50), or large (≥ 0.80). A p-value < 0.05 was considered statistically significant. Intra-rater reliability of ultrasound measurements was evaluated using the intraclass correlation coefficient (ICCs), based on a two-way mixed-effects model (absolute agreement). ICC values were interpreted as follows: poor ( 0.90) 3. Results Data from 27 male participants were included in the analysis. The mean (± SD) age was 34.24 ± 5.1 years, and the mean body mass index was 23.66 ± 2.8 kg/m². 3.1. Muscle Thickness Table 1 presents the bilateral TrA and IO muscle thickness values at rest, during ADIM, and during ADIM with DNF activation. Paired t-tests revealed no statistically significant differences in muscle thickness between the ADIM and ADIM + DNF conditions for either the TrA or IO muscles on both sides (p > 0.05 for all comparisons). Table 1 The measurement of transversus abdominis and internal oblique muscle thickness with and without deep neck flexor coactivation during abdominal drawing-in maneuver. Muscle Without DNF (mm) (mean ± SD) With DNF (mm) (mean ± SD) p-value Right IO 7.55 ± 1.72 7.57 ± 2.18 0.60 Right TrA 7.41 ± 2.02 7.70 ± 2.39 0.39 Left IO 6.00 ± 1.49 6.58 ± 1.78 0.59 Left TrA 5.81 ± 1.65 6.22 ± 1.87 0.13 TrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor Paired t-test was used for statistical analysis. 3.2. Contraction Ratios Table 2 displays the contraction ratios (CRs) of the TrA and IO muscles during ADIM and ADIM + DNF. No significant differences were found in the contraction ratios of the IO muscles with DNF activation (p > 0.05). However, the CR of the TrA muscle showed a statistically significant increase during DNF activation compared to ADIM alone: • Right TrA: t( 18 ) = 2.24, p = 0.03, Cohen’s d = 0.50 (moderate effect size) • Left TrA: t( 18 ) = 2.04, p = 0.04, Cohen’s d = 0.50 (moderate effect size) These findings suggest that DNF activation enhances TrA muscle recruitment during the ADIM, while no such effect was observed for the IO muscles. Table 2 Transversus abdominis and internal oblique muscle contraction ratio with and without deep neck flexor coactivation during abdominal drawing-in maneuver. Muscle Without DNF (mean ± SD) With DNF (mean ± SD) p-value Right IO 0.76 ± 0.11 0.71 ± 0.14 0.19 Right TrA 0.63 ± 0.36 0.74 ± 0.22 0.03 Left IO 0.75 ± 0.15 0.75 ± 0.18 0.91 Left TrA 0.63 ± 0.18 0.72 ± 0.15 0.04 TrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor Paired t-test was used for statistical analysis. 3.3. Reliability Analysis Intra-rater reliability of ultrasonographic measurements for both TrA and IO muscles was excellent across all conditions. Intraclass correlation coefficients (ICCs) are showed Table 3 . These values indicate high to excellent measurement reliability, supporting the consistency and validity of the ultrasonographic assessments in this study. Table 3 Intraclass correlation coefficients of measurements of transversus abdominis and internal oblique muscles at rest, during abdominal drawing-in maneuver, and with deep neck flexor coactivation Condition Right TrA Left TrA Right IO Left IO Resting 0.95 0.96 0.95 0.97 ADIM 0.96 0.96 0.99 0.98 ADIM + DNF 0.97 0.97 0.99 0.99 TrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor, ADIM: Abdominal Draw-in Maneuver 4. Discussion In this study, we investigated the effect of DNF muscle activity on TrA and IO muscle activity during the ADIM using ultrasound measurements of muscle thickness and CR. Our results showed a significant increase in the TrA CR, while muscle thickness remained unchanged. In contrast, there were no significant changes in IO muscle thickness or CR. The postural chain refers to the interconnected alignment of joints, where the position of one joint influences the positioning and movement of others. These chains play a crucial role in posture and movement due to both structural and functional mechanisms. The spine, extending from the cervical vertebrae to the coccyx, exemplifies this interconnected system, as forces and muscle activations are distributed across multiple segments. This relationship is particularly evident between the head and neck regions and the lumbopelvic region, working together to maintain balance and efficient movement ( 1 ). The TrA plays a crucial role in stabilizing the spine and pelvis by increasing intra-abdominal pressure, which enhances spinal rigidity and reduces strain. This stabilization is vital for maintaining posture, especially during dynamic movements like walking, lifting, and reaching ( 8 – 10 ). Therefore, it is important to detect loss of TrA muscle function and to establish rehabilitative exercise programmes. One of the methods to assess the function of the TrA is USI, which a non-invasive and reliable tool used in clinical settings to effectively detects changes in TrA and IO muscles ( 14 ). Both TrA and IO muscle thickness and CR in US measurements provide valuable insights, but the preferred method depends on the research question and clinical application. Muscle thickness is commonly used to assess muscle morphology, while CR offers a relative measure of muscle function rather than just structure (27). For most functional studies, CR is generally considered a better method because it accounts for individual differences in baseline muscle thickness and provides a clearer picture of muscle activation ( 28 ). In our study, the observed increase in TrA CR without a change in muscle thickness suggests that neuromuscular activation, rather than stuctural adaptation, is responsible for the response. This may indicate improved motor control or recruitment efficiency of the TrA muscle rather than structural changes. The deep spinal muscles, which are crucial for postural control and core stability, are believed to interact through the anterior fascial system and deep myofascial chains, facilitating coordinated movement and force transmission across the body. According to Thomas Myers' myofascial meridian theory, the Deep Front Line connects the DNF (longus colli and longus capitis) with the diaphragm, psoas, and pelvic floor muscles, which in turn are linked to the TrA ( 29 ). The anterior cervical fascia, which envelops the DNF, is continuous with the mediastinal fascia and the diaphragm. The diaphragm, in turn, is integrated into the thoracolumbar fascia, which serves as a key structure for TrA activation and force transmission ( 30 ). The observed increase in TrA CR without changes in IO activation supports the hypothesis that DNF activation may selectively enhance TrA engagement through fascial and neuromuscular connections. Core stabilization exercises such as the ADIM, bridging, curl-ups, abdominal stretching, and maximal exhalation have been shown to effectively engage TrA and IO muscles( 11 ). To facilitate the activation of the TrA, the ADIM, which is a common component of lumbar stabilization exercise programs, is particularly recommended ( 11 , 12 ). Previous studies have reported that core exercises combined with lower limb movement ( 18 ), maximal expiration ( 19 ), and simulated weight-bearing ( 20 ) enhance abdominal muscle co-contraction, leading to greater activation of the deep core muscles. The impact of the DNF, the primary stabilizers of the cervical spine, on the activation of TrA and IO remains unexamined. The DNF, including the longus capitis and longus colli, play a crucial role in maintaining postural stability and regulating muscle tone due to their high muscle spindle density( 31 ) which can, in turn, affect the activation of the core muscles, including the TrA and IO. Our results suggest that DNF activation may contribute to improved spinal alignment and sensorimotor integration, facilitating correct movement patterns by enhancing proximal stability through increased TrA activity. However, we did not observe a significant effect of DNF activation on IO muscle activity during the ADIM. Several studies ( 32 – 34 ) have investigated the activation of the TrA and IO muscles during the ADIM using USI and EMG. These studies have consistently found that the TrA shows a significant increase in activation during ADIM, while the IO exhibit a relatively unchanged. The absence of a significant change in IO activity might be due to the different roles of the TrA and IO in core stability. While the TrA primarily functions as a deep stabilizer, the IO contributes to more dynamic movements and trunk rotation, which were not the focus of this study. A key strength of this study is the investigation of DNF influence on core muscles adds valuable insight into the interconnected nature of postural control mechanisms. Unlike previous studies that primarily focused on traditional core stability exercises, our research underscores the potential superiority of integrating cervical and lumbopelvic control strategies for optimizing deep core function. These results pave the way for more effective training interventions that enhance spinal stability and neuromuscular efficiency beyond conventional methods. However, there are some limitations in our study. Springer et al.( 35 ) demonstrated that total abdominal muscle thickness was greater in men, while the representation ratio of the TrA within the total lateral abdominal muscles was higher in women. Similarly, a study by Rho et al.( 36 ) found that asymptomatic men exhibited greater TrA and IO thickness at rest compared to asymptomatic women. Additionally, women showed a greater percentage change in TrA thickness during the ADIM compared to men. Since the abdominal muscle contraction pattern during ADIM differs between men and women, and childbirth can alter abdominal musculature, only male participants were included in this study to reduce variability. However, this limits the generalizability of the findings to females and individuals with musculoskeletal disorders. Additionally, US measurements provide an indirect assessment of muscle activity and do not capture neural activation patterns as precisely as EMG. Furthermore, muscle activation was examined during the ADIM, which primarily targets the TrA rather than the IO, meaning different functional movements might yield different results. Another limitation is the lack of long-term follow-up, making it unclear whether the observed increase in TrA CR translates to functional improvements over time. Future research should include a more diverse population, incorporate EMG for more precise neuromuscular assessments, and employ longitudinal designs to determine the clinical relevance of these findings. These findings may have clinical relevance for rehabilitation professionals designing core stabilization programs, particularly for individuals with spinal instability or postural control deficits. The observed increase in TrA activation in response to DNF engagement suggests that incorporating cervical stability exercises could enhance deep core muscle recruitment. This neuromuscular interplay might be especially beneficial in populations with impaired segmental control or coordination between the cervical and lumbar regions, such as individuals with chronic neck or low back pain. Future studies could investigate whether integrating DNF activation into core exercise regimens improves functional outcomes or reduces symptoms in these clinical populations. 5. Conclusions this preliminary study is hypothesized that DNF activation influences the recruitment patterns of the IO and TrA muscles during the ADIM. Our results showed a significant increase in the TrA CR, while muscle thickness remained unchanged. In contrast, there were no significant changes in IO muscle thickness or CR. The observed increase in TrA CR without changes in IO activation supports the hypothesis that DNF activation may selectively enhance TrA engagement through fascial and neuromuscular connections. This may indicate improved motor control or recruitment efficiency of the TrA muscle rather than structural changes. The combined activation of the DNF and the ADIM may enhance musculoskeletal function by improving postural stability, neuromuscular control, and core muscle recruitment. We propose that this coactivation may lead to greater engagement of the TrA, contributing to improved spinal alignment, proprioceptive awareness, and injury prevention. While the findings highlight a potential neuromuscular interaction between cervical and abdominal muscle systems, the exploratory nature and small sample size limit generalizability. These results provide a basis for future research to further evaluate the integration of cervical stability components into core rehabilitation protocols and to determine their impact in clinical populations. Furthermore, training programs that integrate DNF and ADIM activation may promote superior postural adaptations and functional performance compared to traditional stabilization exercises alone. Abbreviations DNF Deep Neck Flexor TrA Transversus Abdominis IO Internal Oblique ADIM Abdominal Drawing-In Maneuver USI Ultrasound Imaging CCFT Craniocervical Flexion Test CR Contraction Ratio ICC Intraclass Correlation Coefficient SD Standard Deviation EMG Electromyography Declarations Acknowledgements: "Not applicable" Authors' contributions BGBT and BK conceived and designed the study. BGBT and ST collected the data. BGBT performed the statistical analysis. BGBT, ST and BK drafted the manuscript. All authors contributed to the interpretation of data, revised the manuscript critically for important intellectual content, and approved the final version of the manuscript. Funding No specific funding was received from any bodies in the public, commercial or not-for-profit sectors to carry out the work described in this article. Data Availability The datasets are available from the corresponding author upon reasonable request. Ethics approval and consent for publication This study was approved by the Ethics Committee of Gazi University School of Medicine (Approval No: 23, Date: 23.11.2023). All participants were informed about the study procedures and provided written informed consent prior to participation. The study was conducted in accordance with the Declaration of Helsinki. Competing interests All authors declare that they have no conflicts of interest. Clinical trial number: ‘Not applicable’. References Takasaki H, Okubo Y. DEEP NECK FLEXORS IMPACT RECTUS ABDOMINIS MUSCLE ACTIVITY DURING ACTIVE STRAIGHT LEG RAISING. Int J Sports Phys Ther. 2020;15(6):1044-51. Peng B, Yang L, Li Y, Liu T, Liu Y. 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Relationships among lateral abdominal muscles, gender, body mass index, and hand dominance. J Orthop Sports Phys Ther. 2006;36(5):289-97. Rho M, Spitznagle T, Van Dillen L, Maheswari V, Oza S, Prather H. Gender differences on ultrasound imaging of lateral abdominal muscle thickness in asymptomatic adults: a pilot study. Pm r. 2013;5(5):374-80. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6623126","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":464507069,"identity":"e31bc531-9a44-4f1f-890d-60f079c18dff","order_by":0,"name":"Banu Gokcen BAYDOGAN TAN","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7ElEQVRIiWNgGAWjYBACAyCWgDCZD4DYMqRoYUsAsXlI0cJjACYJajFnP2N448MvuzwG/jWfX92oseBhYD98dAM+LZY9OcaWM/uSixkk3m6zzjkGdBhPWtoNvA47kGMmzdvDnNggcXabcQ4bUIsEjxl+LeffgLTUA7WceWac848YLTeAtvD8OJzYwN/D/Di3jQgtljOeFVvObDie2CbBZsac2yfBw0bIL+b8yRtvfPhTndjPf/jx55xvdXL87IeP4dXCwMBhwMDYBoxIiQQ2cASx4VcOAuwPGBj+AGn+A8wfCKseBaNgFIyCkQgAoAVIO9/anuMAAAAASUVORK5CYII=","orcid":"","institution":"Necmettin Erbakan University","correspondingAuthor":true,"prefix":"","firstName":"Banu","middleName":"Gokcen BAYDOGAN","lastName":"TAN","suffix":""},{"id":464507070,"identity":"4828bfbf-eaac-42ff-99c4-5ad5f794b1ea","order_by":1,"name":"Sefa TAN","email":"","orcid":"","institution":"Necmettin Erbakan University","correspondingAuthor":false,"prefix":"","firstName":"Sefa","middleName":"","lastName":"TAN","suffix":""},{"id":464507071,"identity":"ba7508b0-474c-4fcb-b07c-c3df09209114","order_by":2,"name":"Belgin KARAOGLAN","email":"","orcid":"","institution":"Gazi University","correspondingAuthor":false,"prefix":"","firstName":"Belgin","middleName":"","lastName":"KARAOGLAN","suffix":""}],"badges":[],"createdAt":"2025-05-08 19:08:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6623126/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6623126/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":83813334,"identity":"0e5786b1-7d46-4183-a1f4-263269e8c4fb","added_by":"auto","created_at":"2025-06-03 07:22:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1635318,"visible":true,"origin":"","legend":"\u003cp\u003eLegend not included with this version.\u003c/p\u003e","description":"","filename":"Figure.png","url":"https://assets-eu.researchsquare.com/files/rs-6623126/v1/952515b1600c8ab76471045a.png"},{"id":85483665,"identity":"80dabce5-db6e-4f39-8594-89504eacb042","added_by":"auto","created_at":"2025-06-26 11:32:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2990799,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6623126/v1/95bb2e04-69fc-40a7-a783-729ee796bf06.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Influence of deep neck flexor activation on transversus abdominis and internal oblique recruitment during abdominal drawing-in maneuver: An ultrasound imaging study","fulltext":[{"header":"1. Background","content":"\u003cp\u003eMuscle activity in one region of the human body can significantly influence muscle function in other regions, contributing to overall postural stability during movement. The body's musculoskeletal system operates as an interconnected network where forces and activations are distributed across multiple segments particularly evident between the head and neck regions and the lumbopelvic region to maintain balance and efficient motion (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe primary role of the cervical spine is to support the head against gravitational forces while facilitating multidirectional movement. In addition, the cervical spine features an exquisitely sensitive proprioceptive system that conveys the spatial orientation of the head relative to the torso, integrates signals from both the vestibular and ocular systems, and is fundamental to sustaining full-body postural control and balance (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). To fulfill these functions, the cervical spine must maintain robust mechanical stability in both static and dynamic positions (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). This stabilization is facilitated by the coordinated activity of the \u003cb\u003eextensor and flexor muscles\u003c/b\u003e surrounding the cervical spine. Among these, the \u003cb\u003edeep cervical flexors\u003c/b\u003e, including the \u003cb\u003elongus capitis and longus colli\u003c/b\u003e, play a crucial role in \u003cb\u003econtrolling and supporting cervical lordosis\u003c/b\u003e, thereby ensuring the maintenance of \u003cb\u003eoptimal postural alignment\u003c/b\u003e of the cervical spine. These \u003cb\u003edeep segmental muscles\u003c/b\u003e contribute to cervical spine stability by providing \u003cb\u003efine motor control and proprioceptive feedback\u003c/b\u003e, which are essential for postural adjustments and movement precision (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSimilarly, the abdominal muscles, including the Internal Oblique (IO), and Transversus Abdominis (TrA), play a vital role in core stability by facilitating trunk movement, protecting visceral structures, and distributing mechanical loads (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). As the deepest of the abdominal muscles, the \u003cb\u003eTrA functions as a key stabilizer of the spine and pelvis\u003c/b\u003e, providing foundational support before any limb movement occurs (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Its primary function is to \u003cb\u003eincrease intra-abdominal pressure\u003c/b\u003e, which enhances spinal rigidity and reduces excessive strain on the vertebral column (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). This stabilization is essential for maintaining proper posture, particularly during dynamic activities such as walking, lifting, and reaching (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Core stabilization exercises such as the abdominal drawing-in maneuver (ADIM), bridging, curl-ups, abdominal stretching, and maximal exhalation have been shown to effectively engage these muscles (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). To facilitate the activation of the \u003cb\u003eTrA\u003c/b\u003e, the \u003cb\u003eADIM\u003c/b\u003e, which is a common component of lumbar stabilization exercise programs, is particularly recommended (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). A previous study has demonstrated that the ADIM is more effective in facilitating \u003cb\u003eTrA activation\u003c/b\u003e compared to other superficial muscles (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Additionally, the ADIM increases the activity of the \u003cb\u003eIO\u003c/b\u003e muscles (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e), leading to a co-contraction of the \u003cb\u003eMultifidus\u003c/b\u003e muscles (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), which, in turn, contributes to enhanced \u003cb\u003etrunk stability\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eUltrasound imaging (USI)\u003c/b\u003e has been widely employed in clinical settings for several years to quantify changes in abdominal \u003cb\u003emuscle thickness\u003c/b\u003e and \u003cb\u003emuscle activation patterns\u003c/b\u003e, providing a non-invasive and reliable method for evaluating \u003cb\u003emotor control adaptations\u003c/b\u003e following \u003cb\u003ecore stabilization exercises\u003c/b\u003e (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Previous research has demonstrated that USI is an effective tool for detecting \u003cb\u003echanges in TrA and IO muscle thickness and activation during the ADIM\u003c/b\u003e (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Moreover, its validity has been established through comparisons with electromyography (EMG) (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) and \u003cb\u003emagnetic resonance imaging (MRI)\u003c/b\u003e (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e), confirming its accuracy in measuring deep muscle function. Additionally, USI has been shown to have \u003cb\u003ehigh interobserver reliability\u003c/b\u003e in both \u003cb\u003ehealthy individuals\u003c/b\u003e and \u003cb\u003epatients with low back pain (LBP)\u003c/b\u003e (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e), making it a valuable instrument.\u003c/p\u003e \u003cp\u003eEmerging evidence suggests that there are anatomical and functional connections between the cervical and lumbar regions via fascial continuities (e.g., thoracolumbar fascia, deep front line), shared central motor pathways, and proprioceptive integration mechanisms. These interconnections raise the possibility that activation of stabilizing cervical muscles, such as the DNFs, may enhance or modulate the recruitment of abdominal core muscles, particularly the TrA. While previous studies have reported that core exercises combined with \u003cb\u003elower limb movement\u003c/b\u003e (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), \u003cb\u003emaximal expiration\u003c/b\u003e (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e), \u003cb\u003eand simulated weight-bearing\u003c/b\u003e (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) enhance \u003cb\u003eabdominal muscle co-contraction\u003c/b\u003e, leading to greater activation of the deep core muscles, the impact of the deep neck flexor (DNF) on the \u003cb\u003eactivation of TrA and IO\u003c/b\u003e remains unexamined. Given the crucial role of the DNF muscles in cervical spine stability (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) and their potential \u003cb\u003eneuromuscular connections with the trunk\u003c/b\u003e, it is hypothesized that \u003cb\u003eDNF activation influences the recruitment patterns of the IO and TrA muscles\u003c/b\u003e during the \u003cb\u003eADIM\u003c/b\u003e. The aim of this study is to investigate the influence of \u003cb\u003eDNF activation\u003c/b\u003e on the \u003cb\u003erecruitment patterns of the IO and TrA muscles\u003c/b\u003e during the \u003cb\u003eADIM\u003c/b\u003e. By utilizing \u003cb\u003eUSI\u003c/b\u003e, this study seeks to quantify changes in \u003cb\u003emuscle thickness and activation\u003c/b\u003e to determine whether \u003cb\u003eDNF activation enhances deep abdominal muscle engagement\u003c/b\u003e. The findings may contribute to a better understanding of \u003cb\u003eneuromuscular interactions between the cervical and lumbopelvic regions\u003c/b\u003e, providing insights for \u003cb\u003ecore stabilization training and rehabilitation strategies\u003c/b\u003e aimed at improving \u003cb\u003epostural control and musculoskeletal function\u003c/b\u003e.\u003c/p\u003e"},{"header":"2. Materials \u0026 Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Participants\u003c/h2\u003e \u003cp\u003eAn a priori power analysis based on a previous study (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) indicated that 27 participants would be required to detect a moderate effect size (ES\u0026thinsp;=\u0026thinsp;0.5) with an alpha of 0.05 and 80% power. Accordingly, 27 healthy male volunteers aged 18\u0026ndash;45 years were recruited for this cross-sectional study. Inclusion criteria included the absence of neck or back pain, and the cognitive ability to understand and perform the study procedures. Exclusion criteria included a history of trauma or surgery involving the cervical, thoracic, lumbar, or abdominopelvic regions in the past year, presence of kyphoscoliosis (clinically or radiographically), or systemic diseases affecting the musculoskeletal or nervous systems (e.g., Parkinson\u0026rsquo;s disease, multiple sclerosis, malignancy, stroke).\u003c/p\u003e \u003cp\u003eParticipants were recruited voluntarily from hospital staff. They were informed verbally and in writing, and signed informed consent forms. The study adhered to the Declaration of Helsinki and Good Clinical Practice principles and received approval from the Gazi University School of Medicine Ethics Committee (Approval No: 23, Date: 23.11.2023).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Equipment and Ultrasonographic Assessment\u003c/h2\u003e \u003cp\u003eUSI was performed using a MyLab 70 XV system (Esaote Biomedica, Genoa, Italy) with a 5\u0026ndash;12 MHz linear probe and standard ultrasound gel. Bilateral measurements of the TrA and IO muscles were obtained in supine position, following established protocols (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e).The probe was placed transversely, 25 mm anteromedial to the midpoint between the anterior axillary line, iliac crest, and 12th rib. Muscle thickness was measured as the perpendicular distance between hyperechoic fascial borders (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e) (Figure).\u003c/p\u003e \u003cp\u003eEach measurement was performed three times, and the mean value was recorded. Contraction ratio (CR) was calculated as: CR\u0026thinsp;=\u0026thinsp;thickness during ADIM (with or without DNF activation) / resting thickness (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo ensure reliability, the order of measurements was randomized. All assessments were conducted by the same experienced physiatrist, and repeated on the same day to evaluate intra-rater reliability.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Procedures:\u003c/h2\u003e \u003cp\u003eThree experimental conditions were assessed: Resting state / ADIM alone / ADIM with DNF activation\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1. ADIM\u003c/h2\u003e \u003cp\u003eADIM was performed based on Richardson et al.'s protocol (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). Participants lay in a crook-lying position (hips 40\u0026ndash;60\u0026deg; flexed, knees 90\u0026ndash;100\u0026deg; flexed), arms resting by the sides. They were instructed to gently draw the navel toward the spine without moving the pelvis or rib cage. Proper contraction was confirmed by palpation medial to the anterior superior iliac spine, characterized by a slow, deep tension in the abdominal wall held for 10 seconds. This clinical palpation method, though widely used, has limitations due to its subjective nature and reliance on practitioner experience.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.3.2. DNF\u003c/h2\u003e \u003cp\u003eDNF activation was performed using the craniocervical flexion test (CCFT), per the protocol of Jull et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). Participants performed a nodding motion while lying supine, progressively increasing pressure from 20 mmHg to 24 mmHg on a pressure biofeedback unit (Chattanooga Stabilizer, DJO LLC, USA) placed suboccipitally (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). Visual feedback was provided. Participants were trained to minimize superficial muscle involvement and maintain 24 mmHg for the duration of the contraction.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Data Analysis:\u003c/h2\u003e \u003cp\u003eAll statistical analyses were performed using SPSS 22.0 (IBM Corp., Armonk, NY). Normality of the data was assessed using the Shapiro\u0026ndash;Wilk test. For normally distributed variables, a paired t-test was used to compare muscle thickness and contraction ratios between the ADIM alone and ADIM with DNF conditions. Effect sizes were calculated using Cohen\u0026rsquo;s d with 95% confidence intervals (CIs), and interpreted as small (\u0026ge;\u0026thinsp;0.20), moderate (\u0026ge;\u0026thinsp;0.50), or large (\u0026ge;\u0026thinsp;0.80). A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003cp\u003eIntra-rater reliability of ultrasound measurements was evaluated using the intraclass correlation coefficient (ICCs), based on a two-way mixed-effects model (absolute agreement). ICC values were interpreted as follows: poor (\u0026lt;\u0026thinsp;0.50), moderate (0.50 \u0026minus;\u0026thinsp;0.75), good (0.75\u0026ndash;0.90), and excellent (\u0026gt;\u0026thinsp;0.90)\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eData from 27 male participants were included in the analysis. The mean (\u0026plusmn;\u0026thinsp;SD) age was 34.24\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1 years, and the mean body mass index was 23.66\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8 kg/m\u0026sup2;.\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Muscle Thickness\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the bilateral TrA and IO muscle thickness values at rest, during ADIM, and during ADIM with DNF activation. Paired t-tests revealed no statistically significant differences in muscle thickness between the ADIM and ADIM\u0026thinsp;+\u0026thinsp;DNF conditions for either the TrA or IO muscles on both sides (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05 for all comparisons).\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\u003eThe measurement of transversus abdominis and internal oblique muscle thickness with and without deep neck flexor coactivation during abdominal drawing-in maneuver.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuscle\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWithout DNF (mm)\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWith DNF (mm)\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight IO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e7.55\u0026thinsp;\u0026plusmn;\u0026thinsp;1.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.57\u0026thinsp;\u0026plusmn;\u0026thinsp;2.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight TrA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e7.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.70\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft IO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e6.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e6.58\u0026thinsp;\u0026plusmn;\u0026thinsp;1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft TrA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e5.81\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e6.22\u0026thinsp;\u0026plusmn;\u0026thinsp;1.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003cem\u003eTrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003ePaired t-test was used for statistical analysis.\u003c/em\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Contraction Ratios\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays the contraction ratios (CRs) of the TrA and IO muscles during ADIM and ADIM\u0026thinsp;+\u0026thinsp;DNF. No significant differences were found in the contraction ratios of the IO muscles with DNF activation (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, the CR of the TrA muscle showed a statistically significant increase during DNF activation compared to ADIM alone:\u003c/p\u003e \u003cp\u003e\u0026bull; Right TrA: t(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;2.24, p\u0026thinsp;=\u0026thinsp;0.03, Cohen\u0026rsquo;s d\u0026thinsp;=\u0026thinsp;0.50 (moderate effect size)\u003c/p\u003e \u003cp\u003e\u0026bull; Left TrA: t(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;2.04, p\u0026thinsp;=\u0026thinsp;0.04, Cohen\u0026rsquo;s d\u0026thinsp;=\u0026thinsp;0.50 (moderate effect size)\u003c/p\u003e \u003cp\u003eThese findings suggest that DNF activation enhances TrA muscle recruitment during the ADIM, while no such effect was observed for the IO muscles.\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\u003eTransversus abdominis and internal oblique muscle contraction ratio with and without deep neck flexor coactivation during abdominal drawing-in maneuver.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuscle\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWithout DNF\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWith DNF\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight IO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight TrA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft IO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeft TrA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.72\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003cem\u003eTrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003ePaired t-test was used for statistical analysis.\u003c/em\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Reliability Analysis\u003c/h2\u003e \u003cp\u003eIntra-rater reliability of ultrasonographic measurements for both TrA and IO muscles was excellent across all conditions. Intraclass correlation coefficients (ICCs) are showed Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. These values indicate high to excellent measurement reliability, supporting the consistency and validity of the ultrasonographic assessments in this study.\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\u003eIntraclass correlation coefficients of measurements of transversus abdominis and internal oblique muscles at rest, during abdominal drawing-in maneuver, and with deep neck flexor coactivation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCondition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRight TrA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft TrA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight IO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLeft IO\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResting\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eADIM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.98\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eADIM\u0026thinsp;+\u0026thinsp;DNF\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cem\u003eTrA: Transversus Abdominis, IO: Internal Oblique, DNF: Deep Neck Flexor, ADIM: Abdominal Draw-in Maneuver\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eIn this study, we investigated the effect of DNF muscle activity on TrA and IO muscle activity during the ADIM using ultrasound measurements of muscle thickness and CR. Our results showed a significant increase in the TrA CR, while muscle thickness remained unchanged. In contrast, there were no significant changes in IO muscle thickness or CR.\u003c/p\u003e \u003cp\u003eThe postural chain refers to the interconnected alignment of joints, where the position of one joint influences the positioning and movement of others. These chains play a crucial role in posture and movement due to both structural and functional mechanisms. The spine, extending from the cervical vertebrae to the coccyx, exemplifies this interconnected system, as forces and muscle activations are distributed across multiple segments. This relationship is particularly evident between the head and neck regions and the lumbopelvic region, working together to maintain balance and efficient movement (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe TrA plays a crucial role in stabilizing the spine and pelvis by increasing intra-abdominal pressure, which enhances spinal rigidity and reduces strain. This stabilization is vital for maintaining posture, especially during dynamic movements like walking, lifting, and reaching (\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Therefore, it is important to detect loss of TrA muscle function and to establish rehabilitative exercise programmes. One of the methods to assess the function of the TrA is USI, which a non-invasive and reliable tool used in clinical settings to effectively detects changes in TrA and IO muscles (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). Both TrA and IO muscle thickness and CR in US measurements provide valuable insights, but the preferred method depends on the research question and clinical application. Muscle thickness is commonly used to assess muscle morphology, while CR offers a relative measure of muscle function rather than just structure (27). For most functional studies, CR is generally considered a better method because it accounts for individual differences in baseline muscle thickness and provides a clearer picture of muscle activation (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). In our study, the observed increase in TrA CR without a change in muscle thickness suggests that neuromuscular activation, rather than stuctural adaptation, is responsible for the response. This may indicate improved motor control or recruitment efficiency of the TrA muscle rather than structural changes.\u003c/p\u003e \u003cp\u003eThe deep spinal muscles, which are crucial for postural control and core stability, are believed to interact through the anterior fascial system and deep myofascial chains, facilitating coordinated movement and force transmission across the body. According to Thomas Myers' myofascial meridian theory, the Deep Front Line connects the DNF (longus colli and longus capitis) with the diaphragm, psoas, and pelvic floor muscles, which in turn are linked to the TrA (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). The anterior cervical fascia, which envelops the DNF, is continuous with the mediastinal fascia and the diaphragm. The diaphragm, in turn, is integrated into the thoracolumbar fascia, which serves as a key structure for TrA activation and force transmission (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). The observed increase in TrA CR without changes in IO activation supports the hypothesis that DNF activation may selectively enhance TrA engagement through fascial and neuromuscular connections.\u003c/p\u003e \u003cp\u003eCore stabilization exercises such as the ADIM, bridging, curl-ups, abdominal stretching, and maximal exhalation have been shown to effectively engage TrA and IO muscles(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). To facilitate the activation of the TrA, the ADIM, which is a common component of lumbar stabilization exercise programs, is particularly recommended (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Previous studies have reported that core exercises combined with lower limb movement (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), maximal expiration (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e), and simulated weight-bearing (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) enhance abdominal muscle co-contraction, leading to greater activation of the deep core muscles. The impact of the DNF, the primary stabilizers of the cervical spine, on the activation of TrA and IO remains unexamined. The DNF, including the longus capitis and longus colli, play a crucial role in maintaining postural stability and regulating muscle tone due to their high muscle spindle density(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e) which can, in turn, affect the activation of the core muscles, including the TrA and IO. Our results suggest that DNF activation may contribute to improved spinal alignment and sensorimotor integration, facilitating correct movement patterns by enhancing proximal stability through increased TrA activity. However, we did not observe a significant effect of DNF activation on IO muscle activity during the ADIM. Several studies (\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e) have investigated the activation of the TrA and IO muscles during the ADIM using USI and EMG. These studies have consistently found that the TrA shows a significant increase in activation during ADIM, while the IO exhibit a relatively unchanged. The absence of a significant change in IO activity might be due to the different roles of the TrA and IO in core stability. While the TrA primarily functions as a deep stabilizer, the IO contributes to more dynamic movements and trunk rotation, which were not the focus of this study.\u003c/p\u003e \u003cp\u003eA key strength of this study is the investigation of DNF influence on core muscles adds valuable insight into the interconnected nature of postural control mechanisms. Unlike previous studies that primarily focused on traditional core stability exercises, our research underscores the potential superiority of integrating cervical and lumbopelvic control strategies for optimizing deep core function. These results pave the way for more effective training interventions that enhance spinal stability and neuromuscular efficiency beyond conventional methods. However, there are some limitations in our study. Springer et al.(\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e) demonstrated that total abdominal muscle thickness was greater in men, while the representation ratio of the TrA within the total lateral abdominal muscles was higher in women. Similarly, a study by Rho et al.(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e) found that asymptomatic men exhibited greater TrA and IO thickness at rest compared to asymptomatic women. Additionally, women showed a greater percentage change in TrA thickness during the ADIM compared to men. Since the abdominal muscle contraction pattern during ADIM differs between men and women, and childbirth can alter abdominal musculature, only male participants were included in this study to reduce variability. However, this limits the generalizability of the findings to females and individuals with musculoskeletal disorders. Additionally, US measurements provide an indirect assessment of muscle activity and do not capture neural activation patterns as precisely as EMG. Furthermore, muscle activation was examined during the ADIM, which primarily targets the TrA rather than the IO, meaning different functional movements might yield different results. Another limitation is the lack of long-term follow-up, making it unclear whether the observed increase in TrA CR translates to functional improvements over time. Future research should include a more diverse population, incorporate EMG for more precise neuromuscular assessments, and employ longitudinal designs to determine the clinical relevance of these findings.\u003c/p\u003e \u003cp\u003eThese findings may have clinical relevance for rehabilitation professionals designing core stabilization programs, particularly for individuals with spinal instability or postural control deficits. The observed increase in TrA activation in response to DNF engagement suggests that incorporating cervical stability exercises could enhance deep core muscle recruitment. This neuromuscular interplay might be especially beneficial in populations with impaired segmental control or coordination between the cervical and lumbar regions, such as individuals with chronic neck or low back pain. Future studies could investigate whether integrating DNF activation into core exercise regimens improves functional outcomes or reduces symptoms in these clinical populations.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003ethis preliminary study is hypothesized that DNF activation influences the recruitment patterns of the IO and TrA muscles during the ADIM. Our results showed a significant increase in the TrA CR, while muscle thickness remained unchanged. In contrast, there were no significant changes in IO muscle thickness or CR. The observed increase in TrA CR without changes in IO activation supports the hypothesis that DNF activation may selectively enhance TrA engagement through fascial and neuromuscular connections. This may indicate improved motor control or recruitment efficiency of the TrA muscle rather than structural changes. The combined activation of the DNF and the ADIM may enhance musculoskeletal function by improving postural stability, neuromuscular control, and core muscle recruitment. We propose that this coactivation may lead to greater engagement of the TrA, contributing to improved spinal alignment, proprioceptive awareness, and injury prevention. While the findings highlight a potential neuromuscular interaction between cervical and abdominal muscle systems, the exploratory nature and small sample size limit generalizability. These results provide a basis for future research to further evaluate the integration of cervical stability components into core rehabilitation protocols and to determine their impact in clinical populations. Furthermore, training programs that integrate DNF and ADIM activation may promote superior postural adaptations and functional performance compared to traditional stabilization exercises alone.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003ctable border=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eDNF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eDeep Neck Flexor\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eTrA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTransversus Abdominis\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eIO\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eInternal Oblique\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eADIM\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eAbdominal Drawing-In Maneuver\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eUSI\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eUltrasound Imaging\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eCCFT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCraniocervical Flexion Test\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eCR\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eContraction Ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eICC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eIntraclass Correlation Coefficient\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eSD\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eStandard Deviation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003e\u003cstrong\u003eEMG\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eElectromyography\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026quot;Not applicable\u0026quot;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBGBT and BK conceived and designed the study. BGBT and ST collected the data. BGBT performed the statistical analysis. BGBT, ST and BK drafted the manuscript. All authors contributed to the interpretation of data, revised the manuscript critically for important intellectual content, and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo specific funding was received from any bodies in the public, commercial or not-for-profit sectors to carry out the work described in this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Gazi University School of Medicine (Approval No: 23, Date: 23.11.2023). All participants were informed about the study procedures and provided written informed consent prior to participation. The study was conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare that they have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u003c/strong\u003e \u0026lsquo;Not applicable\u0026rsquo;.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eTakasaki H, Okubo Y. DEEP NECK FLEXORS IMPACT RECTUS ABDOMINIS MUSCLE ACTIVITY DURING ACTIVE STRAIGHT LEG RAISING. Int J Sports Phys Ther. 2020;15(6):1044-51.\u003c/li\u003e\n\u003cli\u003ePeng B, Yang L, Li Y, Liu T, Liu Y. Cervical Proprioception Impairment in Neck Pain-Pathophysiology, Clinical Evaluation, and Management: A Narrative Review. Pain Ther. 2021;10(1):143-64.\u003c/li\u003e\n\u003cli\u003eOatis CA. 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Ultrasound assessment of transversus abdominis muscle contraction ratio during abdominal hollowing: a useful tool to distinguish between patients with chronic low back pain and healthy controls? Eur Spine J. 2012;21 Suppl 6(Suppl 6):S750-9.\u003c/li\u003e\n\u003cli\u003eGringmuth R, Jackson C. Therapeutic Exercise For Spinal Segmental Stabilization in Low Back Pain: Scientific Basis and Clinical Approach. JCCA Journal of the Canadian Chiropractic Association Journal de l\u0026apos;Association chiropratique canadienne. 2000;44.\u003c/li\u003e\n\u003cli\u003eJull GA, O\u0026apos;Leary SP, Falla DL. Clinical assessment of the deep cervical flexor muscles: the craniocervical flexion test. J Manipulative Physiol Ther. 2008;31(7):525-33.\u003c/li\u003e\n\u003cli\u003eJull G, Kristjansson E, Dall\u0026apos;Alba P. Impairment in the cervical flexors: a comparison of whiplash and insidious onset neck pain patients. Man Ther. 2004;9(2):89-94.\u003c/li\u003e\n\u003cli\u003eTeyhen DS, Miltenberger CE, Deiters HM, Del Toro YM, Pulliam JN, Childs JD, et al. The use of ultrasound imaging of the abdominal drawing-in maneuver in subjects with low back pain. J Orthop Sports Phys Ther. 2005;35(6):346-55.\u003c/li\u003e\n\u003cli\u003eMangum LC, Henderson K, Murray KP, Saliba SA. Ultrasound Assessment of the Transverse Abdominis During Functional Movement. J Ultrasound Med. 2018;37(5):1225-31.\u003c/li\u003e\n\u003cli\u003eMyers TW, Chaitow L, Juhan D. Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists: Churchill Livingstone; 2001.\u003c/li\u003e\n\u003cli\u003eWilke J, Krause F, Vogt L, Banzer W. What Is Evidence-Based About Myofascial Chains: A Systematic Review. Arch Phys Med Rehabil. 2016;97(3):454-61.\u003c/li\u003e\n\u003cli\u003eJull GA, O\u0026apos;leary SP, Falla DL. Clinical assessment of the deep cervical flexor muscles: the craniocervical flexion test. Journal of manipulative and physiological therapeutics. 2008;31(7):525-33.\u003c/li\u003e\n\u003cli\u003eIshida H, Hirose R, Watanabe S. Comparison of changes in the contraction of the lateral abdominal muscles between the abdominal drawing-in maneuver and breathe held at the maximum expiratory level. Manual therapy. 2012;17(5):427-31.\u003c/li\u003e\n\u003cli\u003eValent\u0026iacute;n-Mazarracin I, Nogaledo-Mart\u0026iacute;n M, L\u0026oacute;pez-de-Uralde-Villanueva I, Fern\u0026aacute;ndez-de-Las-Pe\u0026ntilde;as C, Stokes M, Arias-Bur\u0026iacute;a JL, et al. Reproducibility and Concurrent Validity of Manual Palpation with Rehabilitative Ultrasound Imaging for Assessing Deep Abdominal Muscle Activity: Analysis with Preferential Ratios. Diagnostics (Basel). 2021;11(2).\u003c/li\u003e\n\u003cli\u003eYang KH, Park DJ. Reliability of ultrasound in combination with surface electromyogram for evaluating the activity of abdominal muscles in individuals with and without low back pain. J Exerc Rehabil. 2014;10(4):230-5.\u003c/li\u003e\n\u003cli\u003eSpringer BA, Mielcarek BJ, Nesfield TK, Teyhen DS. Relationships among lateral abdominal muscles, gender, body mass index, and hand dominance. J Orthop Sports Phys Ther. 2006;36(5):289-97.\u003c/li\u003e\n\u003cli\u003eRho M, Spitznagle T, Van Dillen L, Maheswari V, Oza S, Prather H. Gender differences on ultrasound imaging of lateral abdominal muscle thickness in asymptomatic adults: a pilot study. Pm r. 2013;5(5):374-80.\u003c/li\u003e\n\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":"transversus abdominis, abdominal drawing-in maneuver, deep neck flexor, ultrasound imaging","lastPublishedDoi":"10.21203/rs.3.rs-6623126/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6623126/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground/aim:\u003c/strong\u003e Muscle activity in one region of the human body can influence muscle function in other regions, particularly between the cervical and lumbopelvic regions. The deep neck flexors (DNF) play a critical role in cervical spine stability and may have neuromuscular connections with deep core muscles. However, the impact of DNF activation on the transversus abdominis (TrA) and internal oblique (IO) muscles during the abdominal drawing-in maneuver (ADIM) remains unexplored. This study aimed to investigate the influence of DNF activation on TrA and IO muscle activity during the ADIM using ultrasound imaging (USI) to assess changes in muscle thickness and contraction ratio (CR).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and methods:\u003c/strong\u003e Twentyseven healthy male participants (mean age: 34.24 ± 5.1 years, BMI: 23.66 ± 2.8 kg/m²) were recruited. Muscle thickness of the TrA and IO was measured at rest, during the ADIM, and during the ADIM with DNF activation. Contraction ratio (CR) was calculated as: \u003cstrong\u003eCR = thickness during ADIM (with or without DNF activation) / resting thickness \u003c/strong\u003eto assess relative changes in muscle activity. A paired t-test was used to compare muscle thickness and CR across conditions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e No significant changes were observed in TrA and IO muscle thickness with DNF activation (p \u0026gt; 0.05). However, a significant increase in TrA CR was observed bilaterally during DNF activation (right: t = 2.24, p = 0.03, Cohen’s d = 0.50; left: t = 2.04, p = 0.04, Cohen’s d = 0.50), while IO CR remained unchanged.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e The findings suggest that DNF activation selectively enhances TrA recruitment during the ADIM without affecting IO activation. This supports the hypothesis of neuromuscular interactions between the cervical and lumbopelvic regions, possibly mediated by myofascial and proprioceptive connections. Integrating DNF activation into core stabilization exercises may optimize deep core engagement, improve postural stability, and enhance neuromuscular control. Future research should investigate the long-term functional implications and include a broader participant demographic.\u003c/p\u003e","manuscriptTitle":"Influence of deep neck flexor activation on transversus abdominis and internal oblique recruitment during abdominal drawing-in maneuver: An ultrasound imaging study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-03 07:22:06","doi":"10.21203/rs.3.rs-6623126/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":"03a5d95b-904b-42c0-ab57-ab29199d667d","owner":[],"postedDate":"June 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-26T11:23:52+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-03 07:22:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6623126","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6623126","identity":"rs-6623126","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}