Altered transversus abdominis and internal oblique muscle activation during cervical motor control tasks in individuals with chronic neck pain: A surface EMG-based analysis

Abstract

Background

Chronic neck pain (CNP) is associated with disturbances in cervical motor control and altered postural strategies. However, little is known about how cervical motor demands influence the recruitment of deep abdominal stabilizers. This study examined the activation of the transversus abdominis–internal oblique (TrA–IO) during isolated and combined cervical–trunk motor tasks in individuals with CNP.

Objective

To compare TrA–IO activation during the abdominal drawing-in maneuver (ADIM) and ADIM combined with the craniocervical flexion test (CCFT) between individuals with CNP and healthy controls, and to evaluate the reliability of RMS-normalized surface EMG measurements.

Methods

A total of 38 participants (19 individuals with chronic neck pain and 19 age- and sex-matched healthy controls) performed ADIM and ADIM + CCFT tasks while surface EMG recorded bilateral TrA–IO activity. EMG signals were processed using RMS and normalized to maximal voluntary isometric contraction (%MVIC). A 2 × 2 mixed-model ANOVA evaluated group and task effects. Reliability was assessed using ICC, SEM, and MDC.

Results

Both groups showed increased TrA–IO activation during ADIM + CCFT compared to ADIM (p < 0.01). However, the CNP group demonstrated significantly lower activation during the combined task (left: p = 0.026; right: p < 0.001). No associations were found between EMG activation and pain, disability, or symptom duration. Reliability analyses showed excellent test–retest stability (ICC = 0.91–0.99).

Conclusion

Individuals with CNP exhibit impaired ability to increase deep abdominal activation during cervical motor control tasks, indicating disrupted cervico-lumbopelvic synergy. Rehabilitation programs should integrate deep cervical flexor training with core stabilization strategies to address multi-segmental motor control deficits.

Introduction

Chronic neck pain (CNP) is a highly prevalent musculoskeletal disorder and a major contributor to global disability. ¹ Global Burden of Disease (GBD) 2021 estimates indicate that approximately 206 million people worldwide experienced neck pain in 2021, with a pooled point prevalence of 14.4% and an average lifetime prevalence of 23.1%, and that the associated disability burden has continued to increase over recent decades. These findings highlight the persistent and widespread nature of neck pain and its significance as a major public health concern. ²

Despite its widespread occurrence, the mechanisms underlying the persistence and functional impact of CNP are complex and extend beyond nociceptive processes alone. ³ Increasing evidence suggests that altered motor control, ⁴ proprioception, ⁵ and sensorimotor integration ⁶ play a central role in the maintenance of symptoms and movement dysfunction. Deep neck flexor (DNF) muscles, particularly the longus colli and longus capitis, play a central role in segmental cervical stabilization due to their high spindle density and proprioceptive specialization.^7,8 Numerous studies have reported reduced DNF activation, delayed onset timing, and impaired motor control in individuals with CNP, suggesting a disruption of the feedforward mechanisms that maintain cervical stability.^9,10

While dysfunction of the cervical system is well established, emerging evidence suggests that these neuromuscular impairments are not confined to the neck and may extend to more distal segments of the postural control system.^11,12 Studies of spinal pain populations have reported neuromuscular adaptations extending beyond local structures, including delayed or redistributed muscle activation and altered postural control patterns in deeper trunk musculature.^13–15 Collectively, these findings support the concept that persistent sensorimotor alterations in chronic spinal pain may influence multi-segmental motor behaviour rather than reflecting an isolated regional deficit. ¹⁶

Within this multi-segmental framework, the lumbopelvic region, particularly the transversus abdominis (TrA) and internal oblique (IO), plays a fundamental role in anticipatory postural adjustments and load transfer across the spine.^17,18 TrA contraction precedes limb movement and modulates intra-abdominal pressure, contributing to global spinal stiffness.^19,20 Altered recruitment of deep abdominal muscles has been widely reported in chronic low back pain; however, their behavior in the context of CNP remains comparatively underexplored, despite the known role of cervical input in postural regulation.

The cervico-thoraco-lumbopelvic axis is functionally interconnected through myofascial continuities, neural pathways, and shared postural control circuits.^21–23 Impairments in cervical proprioception or DNF activation may influence neuromuscular recruitment strategies beyond the cervical region, potentially affecting the activation of trunk stabilizing muscles. From a motor control perspective, altered afferent input from the cervical region and impaired DNF activation may disrupt feedforward postural strategies, thereby modifying the timing and magnitude of trunk muscle recruitment during tasks requiring anticipatory stabilization.^24,25

Despite growing interest in cervico–trunk interactions, most previous investigations have examined cervical muscle activity in isolation, and the available evidence, largely derived from a limited number of ultrasound-based studies,^26–29 provides only indirect insight into lateral abdominal muscle recruitment in individuals with CNP. Such imaging-based or indirect outcomes offer valuable structural information but limited insight into the timing and magnitude of muscle activation; consequently, the influence of altered cervical motor control on TrA and IO activation during functional tasks remains insufficiently elucidated. Addressing this knowledge gap is critical for improving the understanding of integrated motor control strategies in chronic neck pain and for informing more comprehensive rehabilitation and intervention approaches.

Surface electromyography (sEMG), particularly when processed using root mean square (RMS) and normalized to maximal voluntary isometric contraction (MVIC), allows for dynamic quantification of abdominal muscle activation with high temporal resolution.^30,31 By capturing task-dependent modulation of muscle activity, sEMG provides clinically relevant insight into motor control strategies that cannot be inferred from structural imaging or endurance-based assessments alone. Surprisingly, despite its clinical relevance, no previous sEMG-based study has investigated how deep abdominal muscle activation changes when a cervical motor task is superimposed on a trunk stabilization maneuver in individuals with CNP.

The craniocervical flexion test (CCFT) represents a low-load yet cognitively demanding cervical motor task that challenges feedforward motor control and attentional resources. ³² When combined with an abdominal task, the CCFT introduces an additional motor control demand that requires simultaneous regulation of cervical and trunk stabilization. Within this context, altered cervical motor control may influence trunk muscle recruitment strategies during anticipatory postural tasks, providing a functional framework to examine cervico–trunk motor interactions in individuals with chronic neck pain.

We hypothesized that individuals with chronic neck pain would demonstrate altered TrA–IO activation patterns compared with healthy controls, and that the addition of a cervical motor task would further modify abdominal muscle activation, reflecting impaired integrated motor control. Therefore, the present study aimed to evaluate TrA–IO activation during the abdominal drawing-in maneuver (ADIM) performed alone and in combination with a cervical motor task—the CCFT—in individuals with chronic neck pain and healthy controls, using RMS-normalized surface electromyography. A secondary aim was to examine the test–retest reliability of the sEMG measurements.

Materials and methods

Study design and participants

This single-blinded, cross-sectional study was conducted at the Department of Physical Medicine and Rehabilitation, Gazi University Medical Faculty Hospital between June 2022 and March 2023. A total of 38 participants were included, comprising 19 individuals (15 females and 4 males) with mechanical chronic neck pain (CNP) and 19 age- and sex-matched healthy controls (15 females and 4 males).

Healthy controls were recruited on a voluntary basis from hospital staff through poster announcements displayed within the hospital premises. Participation was entirely voluntary, and no financial compensation or other incentives were provided.

Mechanical chronic neck pain was defined as non-specific neck pain persisting for at least three months, aggravated by neck movements and sustained postures, and without clinical or radiological evidence of radiculopathy, myelopathy, or specific spinal pathology. All diagnoses were confirmed through standardized clinical evaluation performed by a physical medicine and rehabilitation specialist.

The examiner responsible for task supervision and data acquisition was aware of group allocation, whereas the investigator performing EMG signal processing and statistical analyses was blinded to participant group assignment.

All participants provided written informed consent prior to enrollment. The study was approved by the Gazi University Clinical Research Ethics Committee (Approval No: 524/27.06.2022) and was conducted in accordance with the Declaration of Helsinki.

Inclusion and exclusion criteria

Inclusion Criteria

• CNP group: 18–55 years; mechanical neck pain lasting ≥3 months, defined as non-specific neck pain aggravated by neck movements and sustained postures, without clinical or radiological signs of radiculopathy, myelopathy, or specific spinal pathology; diagnosis confirmed by clinical evaluation performed by a physical medicine and rehabilitation specialist; absence of current or previous low back pain within the past year, to avoid confounding effects on lumbopelvic motor control.

• Control group: 18–55 years; no history of neck or low back pain in the past year.

Exclusion Criteria

Participants were excluded if they had:

• Neck or lumbar trauma within the previous year

• Previous interventional treatment for neck pain

• Rheumatologic, inflammatory, infectious, or malignant spinal disease

• Clinical or radiologic signs of disc herniation, radiculopathy, or myelopathy

• History of cervical, shoulder, thoracolumbar, or abdominopelvic surgery

• Neuromuscular diseases, stroke, Parkinson's disease, or multiple sclerosis

• Peripheral neuropathies (e.g., thoracic outlet syndrome, occipital neuralgia)

• Structural postural abnormalities (kyphoscoliosis, visible scoliosis)

• Symptomatic shoulder pathology (restricted range of motion or positive impingement signs)

• Pregnancy

A comprehensive musculoskeletal and neurological examination was applied to both the CNP and healthy control groups to ensure the absence of sensory, motor, or reflex deficits, as well as shoulder dysfunction. The examination included assessment of cervical and shoulder range of motion, manual muscle testing of the upper extremities, sensory and deep tendon reflex evaluation, clinical screening tests to exclude cervical radiculopathy and myelopathy, and shoulder provocative tests to rule out symptomatic shoulder pathology that could influence task performance.

Sample size calculation

No previous sEMG study had investigated TrA–IO activation during a combined cervical-trunk motor task; therefore, a pilot study (n = 12; 6 CNP, 6 controls) was performed. The right-sided TrA–IO %MVIC during the cervical challenge differed between groups (CNP: 86.65 ± 5.46; control: 91.74 ± 5.17), yielding a large effect size (Cohen's d = 0.96).

As specified in the original ethics committee approval, a preliminary pilot phase was prospectively planned to assess feasibility and to inform the sample size calculation. Data from this phase were used exclusively for effect size estimation and protocol refinement and were not included in the final hypothesis testing.

A power analysis in G*Power 3.1.9.4 for a two-tailed independent t-test (α = 0.05) indicated that 38 participants (19 per group) would achieve 81.8% power. This sample size also accommodated potential variability in EMG normalization and inter-session recordings

Clinical assessments

Pain intensity was assessed using the 10-cm Visual Analog Scale (VAS) ³³ at rest and during movement. Disability was quantified using the Neck Disability Index (NDI), with scores reported as percentages. ³⁴ The Turkish-validated version of the NDI was used. ³⁵

Demographic data (age, sex, BMI and symptom duration) were recorded prior to EMG testing. All participants received standardized task familiarization and at least one supervised practice trial.

Electromyographic assessment

EMG Equipment and Signal Processing

Surface EMG recordings of the TrA–IO region were obtained using a Nihon Kohden Neuropack system (Tokyo, Japan). Signals were sampled at 1000 Hz and band-pass filtered between 20–500 Hz, with a 50-Hz notch filter applied to eliminate powerline interference. ³⁶

Raw EMG signals were full-wave rectified and processed using a RMS algorithm with a 100-ms moving window to quantify the amplitude of muscle activation. RMS processing provides a robust estimate of signal power and is widely used to represent the magnitude of neuromuscular activity during sustained and task-dependent contractions. To enable meaningful comparisons across participants and experimental conditions. EMG amplitudes were normalized to MVIC. Normalization to MVIC minimizes inter-individual variability related to electrode placement, subcutaneous tissue characteristics, and signal amplification, and allows muscle activity to be expressed as a percentage of each participant's maximal activation capacity (%MVIC). ³⁷ This approach is recommended in contemporary surface EMG methodology to enhance the interpretability and comparability of activation data across studies and populations. ³⁸

Signal processing was performed using MATLAB (MathWorks, Natick, MA, USA). For each task, RMS values were extracted from a stable 3-s window following initial task stabilization to ensure signal consistency and minimize onset-related variability.

Skin preparation and electrode placement

The electrode site was shaved, abraded, and cleaned with alcohol. Disposable Ag/AgCl bipolar electrodes (20-mm diameter, 20-mm inter-electrode distance) were placed 2 cm medial and inferior to the anterior superior iliac spine (ASIS), aligned with the IO fiber orientation. A reference electrode was positioned over the contralateral ASIS. Due to overlapping fascial layers, sEMG signals represented combined TrA–IO activation, this is consistent with validated surface EMG protocols for this region. ³⁹

Motor tasks

Each motor control task was performed under standardized conditions. Participants completed three repetitions of each task, with each repetition held for approximately 10 s. A rest period of 30 s was provided between repetitions to minimize fatigue. Task order was kept consistent across participants, and standardized verbal instructions were used to ensure uniform task performance.

• (a) Abdominal Drawing-In Maneuver (ADIM)

Performed in crook-lying with controlled diaphragmatic breathing. Participants gently drew the navel inward without pelvic or rib cage motion. Visual and tactile feedback ensured proper deep muscle recruitment. ⁴⁰

• (b) Craniocervical Flexion Test (CCFT)

Participants performed a precise cranio-cervical nodding motion, increasing pressure from 20 to 24 mmHg using a Chattanooga Stabilizer device.^32,41 Real-time feedback minimized SCM compensation. Proper execution was confirmed by the assessor before data collection.

• (c) Maximal Voluntary Isometric Contraction (MVIC)

MVIC was recorded in crook-lying while participants resisted ipsilateral trunk rotation and flexion against manual stabilization. The middle 5 s of a 10-s maximal contraction were used for normalization.^30,37 The same examiner conducted all MVIC trials to reduce inter-tester variability.

Reliability procedure

To examine inter-day reliability, all EMG tasks were repeated after 48 h under identical conditions. The same examiner placed electrodes using anatomical landmarks.

Statistical analysis

Analyses were conducted using SPSS v22 (IBM Corp., NY, USA). Normality was assessed via Shapiro–Wilk tests. Outliers (>3 SD) were examined and none required removal. The statistical analyses were selected to examine both group-related differences and task-specific changes in neuromuscular activity. A mixed-mode analysis of variance (ANOVA) was used to assess the main effects of group (CNP vs. control) and task condition (ADIM vs. ADIM with CCFT), as well as their interaction, allowing evaluation of potential differences in muscle activation across tasks. Primary analysis used a 2 × 2 mixed-model ANOVA with: between-subjects factor: group (CNP vs. control), within-subjects factor: task (ADIM vs. ADIM + CCFT). Levene's test confirmed homogeneity of variances. Effect sizes (partial η²) were reported for all ANOVA outcomes. Bonferroni-adjusted post-hoc tests addressed pairwise differences. Spearman correlations evaluated associations between EMG activation (%MVIC) and clinical variables (age, BMI, symptom duration, VAS, NDI). Statistical significance was set at α < 0.05. This approach has been commonly employed in previous EMG studies focusing on neuromuscular control in musculoskeletal disorders.

Test–retest reliability of the sEMG measurements was evaluated to determine the temporal stability and measurement precision of the TrA–IO activation variables. Intraclass correlation coefficients (ICC 3,1; two-way mixed-effects model, absolute agreement) were calculated for each task condition (ADIM, ADIM + CCFT, and MVIC). Measurement error was quantified using the standard error of measurement (SEM), and the minimum detectable change (MDC) was calculated as SEM × 1.96 × √2. Paired t-tests were performed to assess the presence of systematic bias between repeated measurements. Reliability analyses were conducted separately for each task condition.

Results

Baseline demographic and clinical characteristics

Baseline demographic and clinical characteristics of the participants are presented in Table 1. A total of 38 participants were included, comprising 19 individuals with CNP and 19 age- and sex-matched healthy controls. Each group consisted of 15 females (78.9%) and 4 males (21.1%).

Table 1.

Demographic and clinical characteristics of the participants.

Variable	CNP Group (N = 19)	Control Group (N = 19)	P-Value
Age (Years), Mean ± SD	41.89 ± 8.63	40.80 ± 8.60	0.704
Body Mass Index (KG/M2), Mean ± SD	25.92 ± 2.35	24.86 ± 3.14	0.247
Symptom Duration (Months), Mean ± SD	76.73 ± 62.34	—	—
Vas (rest), CM, Mean ± SD	3.68 ± 2.05	—	—
Vas (Movement), CM, Mean ± SD	7.36 ± 1.25	—	—
Neck Disability Index, Mean ± SD	18.08 ± 11.10	—	—

CNP: Chronic Neck Pain; VAS: Visual Analog Scale; SD: Standard Deviation CM: Centimeter; KG/M²: kilograms per square meter

There were no statistically significant between-group differences in age or BMI (all p > 0.05). In the CNP group, the mean symptom duration was 76.73 ± 62.34 months. Mean pain intensity scores assessed using the visual analog scale (VAS) were 3.68 ± 2.05 cm at rest and 7.36 ± 1.25 cm during movement. The mean NDI score was 18.08 ± 11.10, indicating mild to moderate disability.

Primary outcome: TrA–io muscle activation

Within-Group Effects (Task Effect)

Both groups demonstrated significantly increased TrA–IO activation during the cervical motor task (ADIM + CCFT) compared with standard ADIM (CNP group: left: p = 0.001, right: p = 0.004; Control group: left: p = 0.002, right: p = 0.001). In the CNP group, left-sided TrA–IO activation increased from 65.16 ± 16.30%MVIC during ADIM to 75.94 ± 10.31%MVIC during ADIM + CCFT, while right-sided activation increased from 67.62 ± 20.44%MVIC to 78.91 ± 8.72%MVIC. Similarly, in the healthy control group, left-sided activation increased from 64.62 ± 22.72%MVIC during ADIM to 82.87 ± 9.08%MVIC during ADIM + CCFT, and right-sided activation increased from 67.56 ± 23.38%MVIC to 88.44 ± 6.72%MVIC. The mixed-model ANOVA confirmed a significant main effect of task on muscle activation for both sides (all p < 0.01), with large effect sizes (partial η² = 0.36–0.42).

Between-group effects (group effect during cervical task)

During the ADIM + CCFT condition, the CNP group exhibited significantly lower TrA–IO activation than healthy controls: (Left side: p = 0.026; Right side: p < 0.001). Mixed-model ANOVA demonstrated a significant group × task interaction bilaterally (left: p = 0.031, η² = 0.14; right: p = 0.004, η² = 0.22), indicating that the increase in activation from ADIM to ADIM + CCFT was significantly attenuated in the CNP group.

The EMG findings demonstrated task-dependent variations in TrA–IO muscle activation. Differences in activation patterns were observed between the CNP and control groups, particularly during the combined cervical motor control task, highlighting altered neuromuscular recruitment associated with chronic neck pain. A summary of between-group and within-task sEMG outcomes, including effect sizes and confidence intervals, is presented in Table 2. Figure 1 illustrates group differences across both task conditions.

Table 2.

Summary of surface electromyography Outcomes for transversus abdominis–internal oblique Muscle Activation.

Outcome	Effect Type	Comparison	P-Value	Effect Size (Partial η2)
LEFT TRA–IO (%MVIC)	Within-group (Task)	ADIM vs ADIM + CCFT (CNP)	0.001	0.36
	Within-group (Task)	ADIM vs ADIM + CCFT (Control)	0.002	0.42
	Between-group	CNP vs Control during ADIM + CCFT	0.026	—
	Interaction	Group × Task	0.031	0.14
RIGHT TRA–IO (%MVIC)	Within-group (Task)	ADIM vs ADIM + CCFT (CNP)	0.004	0.38
	Within-group (Task)	ADIM vs ADIM + CCFT (Control)	0.001	0.41
	Between-group	CNP vs Control during ADIM + CCFT	<0.001	—
	Interaction	Group × Task	0.004	0.22

Values summarize within-group task effects (ADIM vs ADIM + CCFT), between-group differences during the cervical motor control task, and group × task interaction effects derived from mixed-model analysis of variance. Effect sizes are reported as partial eta squared (η²). TrA–IO: transversus abdominis–internal oblique; ADIM: abdominal drawing-in maneuver; CCFT: craniocervical flexion test; %MVIC: percentage of maximal voluntary isometric contraction.

Figure 1.

Transversus abdominis–internal oblique muscle activation (% maximal voluntary isometric contraction) during the abdominal drawing-in maneuver performed alone and in combination with the craniocervical flexion test in individuals with chronic neck pain and healthy controls.

Bars represent group mean values for the left and right sides. Asterisks (*) indicate statistically significant between-group differences (CNP vs control) within the ADIM + CCFT condition (p < 0.05). CNP = cronic neck pain; ADIM = abdominal drawing-in maneuver; CCFT = craniocervical flexion test; MVIC = maximal voluntary isometric contraction.

Correlation analyses

Within the CNP group, TrA–IO activation during either task condition showed no significant correlations with: age, BMI, symptom duration, pain intensity (VAS), disability (NDI) (All p > 0.05).

Test–retest reliability

Test–retest reliability analyses demonstrated excellent agreement across all tasks, with ICC values ranging from 0.91 to 0.99. Corresponding SEM and MDC values indicated low measurement error and high temporal stability. Detailed reliability metrics are presented in Table 2.

Discussion

This study examined how cervical motor control demands influence deep abdominal muscle activation in individuals with CNP Table 3. The key finding was that although both groups demonstrated increased TrA–IO activation during the combined ADIM + CCFT task, the magnitude of this increase was significantly lower in the CNP group, as reflected by significant group × task interactions. This pattern suggests a reduced capacity to modulate cervico–lumbopelvic muscle recruitment when cervical motor control demands increase, rather than a generalized deficit in abdominal muscle activation. The greater abdominal activation observed in healthy individuals during the combined task is consistent with the concept of anticipatory postural adjustments and the cooperative function of cervical and lumbopelvic stabilizers under increased sensorimotor challenge.

Table 3.

Test–retest reliability of root mean square-normalized transversus abdominis–internal oblique surface electromyographic measures.

Task Condition	Side	ICC (3,1)	SEM	MDC
ADIM	Right	0.97	2.37	6.57
	Left	0.91	4.03	11.18
MVIC	Right	0.99	3.68	10.21
	Left	0.99	2.75	7.62
ADIM + CCFT	Right	0.97	2.15	5.97
	Left	0.98	1.78	4.94

ADIM = abdominal drawing-in maneuver; CCFT = craniocervical flexion test; ICC = intraclass correlation coefficient; MDC = minimum detectable change; MVIC = maximal voluntary isometric contraction; SEM = standard error of measurement.

From a motor control perspective, these findings suggest that CNP may be associated with altered coordination across spinal regions during tasks requiring simultaneous cervical and trunk stabilization. Effective anticipatory postural control relies on the integration of cervical proprioceptive input and feedforward activation of trunk stabilizers.^42,43 Previous studies have consistently shown that individuals with CNP exhibit impaired DNF performance, delayed activation timing, and altered proprioception, all of which may compromise cervical sensorimotor integration.^4–6 Motor control adaptations in the presence of pain are known to be task-specific and direction-specific, reflecting the functional role of the involved muscles as agonists or antagonists within a given task. ⁴⁴ Accordingly, when a precise cervical motor task such as the CCFT is superimposed on the ADIM, the neuromuscular system is required to flexibly scale trunk muscle activation while maintaining accurate cervical control. The reduced TrA–IO augmentation observed in the CNP group may therefore reflect a diminished capacity to adapt motor output under increased sensorimotor and attentional demands, rather than a generalized deficit in baseline abdominal muscle activation.

Another mechanism that may contribute to the attenuated TrA–IO activation observed in the CNP group is the influence of chronic pain on central motor planning,^10,45,46 which may lead to protective or less efficient movement strategies and reduced recruitment of deep stabilizing muscles during complex tasks. Additionally, deficits in cervical proprioception may impair anticipatory postural adjustments, resulting in reduced preparatory recruitment of the TrA–IO complex during cervical loading. The myofascial and neurophysiological continuity of the cervico-thoraco-lumbopelvic axis^23,47 provides a plausible biomechanical and neurophysiologic framework for this reduced synergy. Given these interacting mechanisms, the attenuated abdominal activation observed here likely reflects a combination of altered sensorimotor integration and disrupted feedforward motor planning rather than a single-source deficit.

The present findings are consistent with emerging evidence suggesting that neuromuscular adaptations in CNP extend beyond the cervical region. Recent studies^13–15 have demonstrated that individuals with CNP exhibit reduced endurance and altered performance of trunk flexor, extensor, and lateral flexor muscles compared with asymptomatic controls, suggesting a more global neuromuscular involvement rather than an isolated cervical deficit. These findings support the concept that CNP is associated with impaired multi-segmental motor control, in which deficits in cervical stabilization may influence trunk muscle function during postural and functional tasks. However, existing evidence has largely focused on static or endurance-based measures of trunk performance, providing limited insight into task-dependent activation patterns and the dynamic modulation of deep abdominal muscles during combined cervical and trunk motor demands.

Ultrasound-based studies^27,28 demonstrated that women with CNP showed reduced TrA thickness change during ADIM when DNF activation was added, indicating that increased cervical motor demands can influence lumbopelvic muscle behavior during task performance. Notably, these studies did not report differences in resting transversus abdominis thickness between groups, emphasizing that the observed alterations were task-dependent rather than structural. In contrast, a recent ultrasound elastography study ²⁹ reported changes in TrA thickness and mechanical properties in individuals with CNP and cervical hypolordosis; however, muscle properties were assessed at rest, without a functional or task-based motor challenge, limiting the extent to which these findings can be interpreted as reflecting motor control behavior. Together with evidence from Moseley ²⁴ showing that subacute neck pain predicts poorer abdominal draw-in performance and later development of low back pain, these findings support the concept of a bidirectional interaction within the cervico–thoraco–lumbopelvic system. Similarly, Thongprasert et al. ⁴⁸ reported abnormal DNF performance in patients with low back pain, suggesting shared motor control pathways across spinal segments. Our results extend this literature by demonstrating impaired activation amplitude using RMS-normalized surface EMG, offering a complementary and dynamic perspective on how abdominal muscles respond to combined cervical and trunk motor demands. Together, these findings support the concept that CNP may be associated with distributed motor control adaptations affecting intersegmental coordination.

No significant associations were observed between TrA–IO activation and pain intensity, disability, or symptom duration. This finding should not be interpreted as evidence that abdominal muscle activation is clinically irrelevant in CNP. Rather, it suggests that task-dependent neuromuscular behavior may represent a motor control characteristic that is not directly driven by symptom severity. Within this context, surface EMG is not intended to function as a surrogate marker of pain or disability, but as a mechanistic tool to characterize how the neuromuscular system organizes movement under specific task constraints. The absence of correlations with clinical measures implies that altered TrA–IO scaling during cervical challenge may reflect an underlying coordination strategy rather than a symptom-dependent phenomenon.

The clinical relevance of these findings is noteworthy. Rehabilitation programs for CNP often focus on DNF strengthening in isolation^49,50; however, the reduced abdominal activation observed during cervical motor control suggests that interventions may be more effective when they integrate cervical and lumbopelvic motor training. Combined approaches targeting DNF activation, TrA recruitment, postural control, and proprioceptive re-education may help restore multi-segmental coordination and improve functional outcome.

These insights suggest that multi-regional rehabilitation paradigms emphasizing coordinated activation across cervical and lumbopelvic subsystems may warrant further consideration. Incorporating integrated motor control exercises, dynamic anticipatory strategies, and sensorimotor retraining may offer potential advantages over isolated cervical strengthening approaches; however, their clinical effectiveness should be confirmed in future interventional studies. Assessment of trunk muscle behavior may also be relevant in some patients with CNP, even when symptoms appear localized.

This study benefits from the use of standardized EMG acquisition, RMS processing, and MVIC normalization procedures, alongside excellent inter-day test–retest reliability, thereby strengthening confidence in the robustness of the observed neuromuscular activation patterns. However, several limitations should be acknowledged when interpreting the present findings. First, the surface EMG configuration used in this study reflects combined activity of the TrA and IO muscles, as electrodes were placed over their overlapping fascial region. This methodological constraint, which is inherent to surface EMG recordings obtained from this anatomical site, precludes differentiation of the individual contributions of these muscles and has been well documented in previous studies. ³⁹ Second, several factors that may influence neuromuscular responses during the combined cervical–trunk task were not instrumentally assessed. Cervical range of motion, movement velocity, and qualitative performance during the CCFT were not quantified and may have differed between groups. Subtle restrictions in cervical mobility or compensatory movement strategies could therefore have affected trunk muscle activation during the combined task. In addition, cognitive load, attentional demands, and psychosocial factors such as kinesiophobia—which are known to influence motor behavior in chronic pain—were not evaluated. The absence of associations between EMG activation and clinical measures may partly reflect the contribution of such unmeasured variables. Third, although excluding individuals with concomitant low back pain improved internal validity by minimizing confounding lumbopelvic motor impairments, this criterion may limit the generalizability of the findings to broader clinical populations in which neck and low back pain frequently coexist. Finally, the cross-sectional design of the study precludes causal inference, and it remains unclear whether the observed alterations in abdominal muscle activation represent a consequence of chronic neck pain or a predisposing motor control characteristic.

Future research should incorporate complementary assessment modalities, such as high-density EMG and three-dimensional motion analysis, to enable a more detailed evaluation of multi-segmental motor adaptations. Such approaches may facilitate a finer characterization of cervico-lumbopelvic coupling and neuromotor control strategies in individuals with chronic neck pain. In addition, longitudinal and interventional study designs are warranted to clarify the temporal relationship between altered trunk muscle activation and the development or persistence of chronic neck pain.

In summary, individuals with chronic neck pain demonstrate a diminished capacity to augment deep abdominal muscle activation during cervical motor control tasks, reflecting impaired cervico-lumbopelvic synergy. Rehabilitation strategies that integrate cervical motor control training with targeted core stabilization may better address the underlying neuromuscular deficits observed in this population. These findings underscore the importance of adopting a multi-segmental perspective when assessing and managing chronic neck pain, acknowledging that cervical dysfunction may have downstream consequences on trunk stability and overall postural control.