Trunk muscle thickness and sprint, agility, and jump performance in competitive football players

Abstract

Background

Trunk musculature is increasingly recognized for its role in athletic performance, yet remains less studied than lower limb muscles. This study aimed to examine the associations between trunk muscle thickness and sprint, agility, and jump performance in competitive male football players.

Methods

Fifteen male football players (tier 3; mean age: 19.73 ± 1.75 years; training experience: 8.06 ± 1.57 years) participated. Thickness of five trunk muscles was measured at rest using B-mode ultrasound. Sprint (20-m), agility (Pro-Agility), and countermovement jump (CMJ) tests were conducted. To control for type I error across 15 comparisons, Bonferroni correction was applied (α_adj = 0.0033). Significant associations were further examined using linear regression.

Results

After adjustment for multiple testing, transversus abdominis and internal oblique thickness were significantly associated with 20 m sprint time (r = − 0.739 to − 0.746, p ≤ 0.002). These muscles were also significantly associated with agility performance (r = − 0.704 to − 0.746, p < 0.003). No significant associations were found between trunk muscle thickness and CMJ performance after correction. No bilateral asymmetries were detected (all p > 0.05; d < 0.2).

Conclusion

Greater thickness of specific deep anterior trunk muscles appears to be associated with sprint and agility performance in competitive football players. These findings suggest that deep trunk morphology may be associated with sprint and change-of-direction performance, although causal relationships cannot be inferred due to the cross-sectional design.

Introduction

Football is a high-intensity, multidirectional sport characterized by rapid acceleration, abrupt directional changes, and explosive vertical actions. These performance demands rely on the integrated functioning of the neuromuscular and musculoskeletal systems. In this context, the ability of skeletal muscles to generate force, coordinate movement, and maintain mechanical efficiency is essential for optimal performance [1, 2]. Muscle thickness plays a fundamental role in optimizing these functions during dynamic and high-intensity activities [3]. While numerous studies have investigated the relationship between muscle thickness and athletic performance, most of this research has specifically focused on lower-limb muscles, emphasizing their role in sprinting, jumping, and directional changes [4–6]. However, the contribution of trunk musculature to these performance outcomes has received relatively little attention [7], despite its central role in force transmission, stability, and coordination during dynamic movements [8].

Trunk musculature serves as a biomechanical bridge between the upper and lower extremities, enabling effective transfer of force across the kinetic chain [9]. This central positioning allows trunk muscles to contribute not only to segmental stabilization but also to the generation and control of movement during sport-specific tasks [10]. In this context, thickness of trunk muscles may represent an important morphological factor influencing force transmission and movement control. This may be explained by the relationship between muscle thickness and force-generating capacity, as greater muscle thickness is generally associated with increased cross-sectional area and muscle strength, which are key determinants of mechanical output during dynamic tasks [11, 12]. Furthermore, deep muscles such as the transversus abdominis and multifidus provide segmental support and enhance lumbopelvic stability, while larger superficial muscles including the rectus abdominis and obliques contribute to torque production and trunk rotation [13].

In dynamic sports like football, the ability of the trunk to maintain alignment and minimize energy leaks becomes critical for optimizing force transfer and reducing compensatory motion across the kinetic chain [14]. Recent work further supports this, indicating that trained trunk musculature can maintain equivalent trunk stability with lower activation levels, reflecting improved neuromuscular efficiency [15]. While these adaptations reflect functional improvements in motor control, muscle thickness of the trunk may also play a role in performance outcomes. Recent findings suggest that greater trunk muscle thickness is associated with reduced trunk displacement during reactive agility tasks, indicating a potential role in enhancing postural control and movement efficiency in high-speed directional changes [16, 17].

While trunk muscles are crucial for athletic movement, the specific contribution of trunk muscle thickness to sprinting, jumping, and agility performance remains underexplored. Most research still emphasizes lower-limb morphology. Given the functional demands of football and the biomechanical role of the trunk in kinetic chain efficiency, there is a need to clarify how trunk muscle thickness relates to key performance in football. Furthermore, the role of bilateral asymmetry in trunk muscles remains paradoxical. While some evidence points toward symmetry as a sign of neuromuscular balance [18], other studies have associated minor asymmetries with sport-specific adaptations or even protective mechanisms [19]. This contradiction underscores the need to better understand the functional relevance of muscle symmetry in athletic populations.

To our knowledge, this is the first study to investigate the association between trunk muscle thickness and explosive performance outcomes in competitive youth football players using ultrasound imaging. While trunk muscle morphology has been previously linked to spinal health and postural control, its relationship to sprint, agility, and jump performance remains underexplored.

Such findings would provide valuable insights for coaches and performance specialists seeking to optimize athletic output through a better understanding of trunk muscle morphology. The aim of this study was to investigate the associations between trunk muscle thickness and sprint, agility, and jump performance in competitive football players. A secondary objective was to evaluate the presence of side-to-side asymmetry in trunk muscle thickness. Based on previous findings [16, 17], it was hypothesized that trunk muscle thickness, particularly in deep stabilizers such as the transversus abdominis and multifidus, would be positively associated with jumping performance and negatively with sprint and agility times. Furthermore, it was hypothesized that no significant bilateral asymmetry would be observed in trunk muscle thicknesses.

Methods

Study design and participants

This cross-sectional study was approved by the Scientific Research and Publication Ethics Committee of Inonu University (Approval no: 2024/4451), and was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki.

Written informed consent was obtained from all participants and their legal guardians prior to participation. Exclusion criteria included any history of musculoskeletal injury within the past six months, neurological disorders, or prior surgical interventions involving the trunk or lower extremities. Participants were competitive male football players classified as Tier 3 athletes [20], denoting highly trained individuals competing at the national or provincial level, with approximately 8 years of systematic football training. They were regularly engaged in football training consisting of approximately 4–5 sessions per week, including technical–tactical drills and match play, with moderate-to-high intensity typical of in-season conditions.

Sample size estimation

A priori power analysis was conducted using G*Power 3.1.9.3 (Heinrich Heine University, Düsseldorf, Germany) to determine the required sample size for a two-tailed Pearson correlation analysis. Based on previous findings reporting a significant moderate negative correlation between transversus abdominis muscle thickness and 100-m sprint time (ρ = −0.691) [7], the analysis indicated that a minimum of 15 participants would be required to achieve 85% statistical power (1-β = 0.85) at an alpha level of 0.05. Accordingly, fifteen youth male football players participated in the study (age = 19.73 ± 1.75 years; height = 1.76 ± 0.06 m; weight = 67.17 ± 6.34 kg).

Variables and outcome measures

The primary variables of the study included trunk muscle thickness (mm) measured for the transversus abdominis (TrA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), and lumbar multifidus (LM). Performance variables included 20-m sprint time (s), agility time (s; Pro-Agility test), and countermovement jump (CMJ) height (cm).

Assessment procedures

All assessments were conducted by experienced personnel, with ultrasound measurements performed by an experienced radiologist and performance tests administered by an experienced sports scientist, following standardized procedures. Prior to testing, participants completed a standardized warm-up consisting of 5 min of light jogging, followed by dynamic stretching and submaximal practice trials. All assessments were conducted in an indoor sports facility of the Faculty of Sport Sciences under controlled environmental conditions to ensure consistency. Participants were instructed to refrain from strenuous physical activity 48 h before testing and to maintain their usual diet and sleep habits. Assessments were conducted across two non-consecutive days during the competitive season. On the first day, anthropometric and ultrasound assessments were performed, followed by athletic performance tests on the second day, as illustrated in the study flow diagram (Fig. 1).

Fig. 1.

Summary of study design

Body composition

Standardized anthropometric assessments were performed in accordance with the guidelines of the International Society for the Advancement of Kinanthropometry, ensuring a technical error of measurement below 1% [21]. Stature was recorded to the nearest 0.1 cm using a portable stadiometer (Seca, Bonn, Germany), and body mass was measured using a calibrated digital scale (Model 813, Seca, Hamburg, Germany).

Muscle thickness assessment

Ultrasound imaging was performed using a B-mode ultrasound unit (HS-2100, Honda Electronic, Japan) equipped with a 7.5 MHz linear-array transducer. All ultrasound assessments were performed by a single experienced radiologist who was blinded to the participants’ performance test results to minimize measurement bias. To ensure measurement consistency, each muscle was evaluated three times, and the mean value was used for analysis. Intra-rater reliability was assessed using intraclass correlation coefficients (ICC). All ICC values exceeded 0.90, indicating excellent measurement reliability across all muscle groups. Muscle thickness measurements for all trunk muscles were performed bilaterally to ensure a comprehensive assessment of potential side-to-side variations. A standardized ultrasound protocol was employed for all measurements to ensure reproducibility across different trunk muscle groups (Fig. 2).

Fig. 2.

Representative ultrasound images of trunk muscles: (A): external oblique (EO), internal oblique (IO), transversus abdominis (TrA); (B): rectus abdominis (RA); (C): lumbar multifidus (LM)

Abdominal muscle thickness was assessed bilaterally at rest. Participants were positioned in a supine posture with knees flexed, and anatomical landmarks were defined as the inferior margin of the rib cage and the iliac crest [22]. To obtain clear images of the anterolateral abdominal wall muscles-namely the transversus abdominis, internal oblique, and external oblique-the transducer was placed transversely over the right side of the abdominal wall along the anterior axillary line, midway between the 12th rib and the iliac crest. For the rectus abdominis, the transducer was positioned 2–3 cm superior to the umbilicus along the midline. All images were captured at the end of a relaxed expiration, based on visual confirmation of abdominal content stabilization, to minimize intra-abdominal pressure variability and ensure consistent resting muscle morphology. Two separate images were recorded for each muscle at rest, and the average of these two measurements was used for statistical analysis. A 30-minute interval was maintained between measurements, during which participants were fully informed about the procedure and allowed to rest. All measurements were taken during normal tidal breathing, with muscle thickness recorded immediately after expiration [22, 23].

Lumbar multifidus muscle thickness was measured bilaterally at the level of the L5 vertebra. Participants were positioned prone with both arms resting alongside the body in a relaxed posture. The transducer was initially aligned longitudinally along the spine, centered over the L4 spinous process, and then gently rotated medially and moved laterally to visualize the L4/L5 zygapophyseal joint. Optimal imaging was achieved when the lumbar multifidus muscle was clearly visible directly beneath the transducer. Measurements were obtained using the system’s built-in measurement software, with lumbar multifidus thickness defined as the vertical distance between the facet joint and the superficial border of the lumbar multifidus muscle at the subcutaneous tissue level [24].

Linear sprint measurement

Linear sprint performance was assessed using a 20-meter sprint test. Sprint times were recorded in seconds using a dual-beam electronic timing gate system (Smart Speed; Fusion Sport, Australia) placed at the start and finish lines. Participants began each sprint from a standing start 30 cm behind the first gate to ensure accurate timing. To minimize the effects of fatigue and to allow for adequate recovery of phosphocreatine stores between efforts, a passive rest interval of 3–5 min was provided between each of the three trials. The best sprint time (s) was used for subsequent analysis [25].

Agility measurement

Agility performance was assessed using the Pro-Agility Test. The test was conducted on a flat, non-slippery surface with three markers aligned in a straight line, each placed 4.57 m apart. Athletes began in a three-point stance centered at the middle marker and, upon the start signal, sprinted 4.57 m to the right marker, touched the line with their hand, immediately sprinted 9.14 m to the left marker, touched the line, and then sprinted back 4.57 m to the starting point. Timing was recorded in seconds using a dual-beam electronic timing gate system (Smart Speed; Fusion Sport, Australia) placed at the start/finish line. Prior to the actual test trials, participants performed two submaximal familiarization runs to minimize learning effects. This was followed by three maximal-effort test trials, each separated by a 3-minute passive rest interval to ensure adequate recovery. The fastest recorded time (s) was used for subsequent analysis [26].

Jump measurement

Countermovement jump performance was assessed using an electronic contact mat (Fusion Sport, Australia). Participants began each attempt from a standing position with their hands placed on their hips to minimize upper body contribution. They were instructed to perform a rapid downward movement followed by an immediate maximal jump. Each participant completed three trials, with 2-minute passive rest intervals between attempts to allow for sufficient neuromuscular recovery. The highest jump height (cm) was recorded and used for subsequent analysis [27]. Although countermovement jump performance is commonly used to estimate lower-limb muscle power, the present study focused on jump height (cm) as the primary outcome to maintain methodological consistency and avoid the inclusion of additional derived variables beyond the primary study objectives.

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics version 23 (IBM Corp., Armonk, NY, USA). Descriptive data are presented as means and standard deviations. Normality and homogeneity were assessed via Shapiro-Wilk and Levene’s tests, respectively. Paired sample t-tests were used to compare bilateral muscle thickness values. Effect sizes for pairwise comparisons were calculated using Cohen’s d and classified as trivial (< 0.2), small (0.2–0.6), moderate (0.6–1.2), large (1.2–2.0), and very large (> 2.0). Pearson correlation analyses were performed using bilateral mean muscle thickness values to examine the relationships between trunk muscle morphology and athletic performance outcomes. The magnitude of the correlation was interpreted as follows: trivial (r < 0.10), small (0.10 ≤ r < 0.30), moderate (0.30 ≤ r < 0.50), large (0.50 ≤ r < 0.70), very large (0.70 ≤ r < 0.90), nearly perfect (0.90 ≤ r < 1.00), and perfect (r = 1.00). To control for type I error due to multiple testing (5 trunk muscles × 3 performance outcomes = 15 comparisons), Bonferroni correction was applied, and the adjusted significance threshold was set at αadj = 0.0033. For correlations that met the adjusted significance criterion, simple linear regression analyses were performed to quantify the proportion of shared variance. The intraclass correlation coefficient was calculated to assess the reliability of muscle thickness measurements. 95% confidence intervals were reported where appropriate.

Results

Descriptive statistics for participant demographics and physical performance are presented in Table 1. Participants demonstrated homogenous anthropometric profiles and showed consistent performance across all tests, as indicated by narrow standard deviations and confidence intervals.

Table 1.

Descriptive characteristics and physical performance outcomes of male football players (n = 15)

Variables	Mean ± standard deviation	95% confidence interval
Age (years)	19.73 ± 1.75	18.76, 20.70
Height (m)	1.76 ± 0.06	1.72, 1.79
Weight (kg)	67.17 ± 6.34	63.66, 70.68
Body mass index (kg/m2)	21.67 ± 1.55	20.80, 22.53
Training experience (years)	8.06 ± 1.57	7.19, 8.94
Linear sprint time (s)	2.93 ± 0.15	2.85, 3.02
Agility time (s)	4.83 ± 0.20	4.72, 4.95
Jump height (cm)	34.52 ± 2.90	32.90, 36.13

Figure 3 illustrates the comparison of muscle thickness between the right and left sides for various trunk muscles. No statistically significant bilateral differences were found in any of the measured muscles. Specifically, the thickness of the transversus abdominis was similar on both sides (t = -0.706, p = 0.492, d = 0.18). The internal oblique measurements were also comparable (t = -0.342, p = 0.737, d = 0.09), as were those of the external oblique (t = -0.643, p = 0.530, d = 0.17). Similar results were observed for the rectus abdominis (t = -0.520, p = 0.611, d = 0.13) and the lumbar multifidus (t = -0.310, p = 0.761, d = 0.08).

Fig. 3.

Bilateral comparison of trunk muscle thickness measurements (right vs. left) along with bilateral mean values (Mean). Values are presented as mean ± SD

All effect sizes were classified as trivial (d < 0.2), indicating negligible differences between sides. Given the absence of statistically significant bilateral differences and the trivial magnitude of these effects, bilateral mean values were used in subsequent analyses to provide a more representative and methodologically transparent measure of trunk muscle thickness.

Measurement reliability was high across all muscles, with intraclass correlation coefficients ranging from 0.90 to 0.98.

Pearson correlation coefficients based on bilateral mean muscle thickness values are presented in Table 2. After applying Bonferroni correction for multiple comparisons (α_adj = 0.0033), significant associations were observed between 20 m sprint time and the thickness of the transversus abdominis (r = − 0.739, p = 0.002) and internal oblique (r = − 0.746, p = 0.001). In addition, both transversus abdominis (r = − 0.704, p = 0.003) and internal oblique thickness (r = − 0.746, p = 0.001) were significantly associated with agility performance, indicating that these relationships extend beyond linear sprint tasks.

Table 2.

Pearson correlation coefficients between bilateral mean trunk muscle thickness and linear sprint, agility, and jump performance in male football players

Transversus abdominis (mm)	r value	p value	95% CI
Linear sprint time (s)	-0.739	0.002*	-0.908, -0.365
Agility time (s)	-0.704	0.003*	-0.894, -0.300
Jump height (cm)	0.493	0.062	-0.026, 0.803
Internal oblique (mm)	r value	p value	95% CI
Linear sprint time (s)	-0.746	0.001*	-0.910, -0.378
Agility time (s)	-0.746	0.001*	-0.910, -0.378
Jump height (cm)	0.550	0.034	0.053, 0.829
External oblique (mm)	r value	p value	95% CI
Linear sprint time (s)	-0.257	0.355	-0.680, 0.294
Agility time (s)	-0.385	0.156	-0.749, 0.159
Jump height (cm)	0.326	0.235	-0.224, 0.718
Rectus abdominis (mm)	r value	p value	95% CI
Linear sprint time (s)	-0.461	0.084	-0.787, 0.067
Agility time (s)	-0.426	0.113	-0.770, 0.110
Jump height (cm)	0.427	0.113	-0.109, 0.771
Lumbar multifidus (mm)	r value	p value	95% CI
Linear sprint time (s)	-0.484	0.067	-0.798, 0.038
Agility time (s)	-0.485	0.067	-0.799, 0.036
Jump height (cm)	0.535	0.040	0.031, 0.822

(^*=Bonferroni-adjusted significance threshold: p < 0.0033)

No statistically significant associations were found between trunk muscle thickness and countermovement jump performance after correction for multiple testing. Similarly, external oblique, rectus abdominis, and lumbar multifidus thickness were not significantly associated with any performance variable following Bonferroni adjustment.

Based on the correlation findings, simple linear regression analyses were conducted to quantify the proportion of shared variance for associations that remained significant after Bonferroni correction (αadj = 0.0033). Transversus abdominis thickness was associated with 20 m sprint time (F_(1,13) = 15.603, p = 0.002), while internal oblique thickness showed a similar association (F_(1,13) = 16.318, p = 0.001). In addition, both transversus abdominis (F_(1,13) = 12.771, p = 0.003) and internal oblique thickness (F_(1,13) = 16.277, p = 0.001) were also associated with agility performance (Fig. 4). No other trunk muscle thickness demonstrated a statistically significant association with sprint performance after adjustment for multiple testing.

Fig. 4.

Simple linear regression analyses illustrating the associations between transversus abdominis and internal oblique thickness and sprint and agility performance. Solid lines represent regression slopes with 95% confidence intervals

Discussion

The present study examined the relationship between trunk muscle thickness and explosive performance measures in competitive male football players. After strict correction for multiple testing, transversus abdominis and internal oblique thickness were associated with both 20 m sprint and agility performance, suggesting a potential involvement of deep anterior trunk morphology in tasks requiring both acceleration and rapid changes of direction. These findings further suggest that specific deep anterior trunk muscles may be related to sprint and agility in football players. In contrast, no significant associations were observed with jump performance after adjustment. Nevertheless, given the cross-sectional design of the study, these findings should be interpreted as associations rather than causal relationships.

Transversus abdominis in relation to sprint and agility performance

Lower extremity muscle architecture has been extensively investigated in relation to athletic performance, with greater muscle thickness generally associated with enhanced high-intensity performance outcomes [28, 29]. Although the present study focused on trunk musculature, increased muscle thickness reflects greater cross-sectional area and force transmission potential [30, 31]. However, the present findings indicate that not all trunk muscles demonstrate equivalent performance relevance, and that associations appear to be task-specific.

In particular, a significant association between transversus abdominis thickness and sprint performance aligns with findings in collegiate male sprinters, where 100-m sprint time was inversely associated with transversus abdominis thickness (ρ = −0.691) [7]. In that investigation, multifidus thickness demonstrated a weaker and non-significant relationship, suggesting a more specific contribution of the deep anterior trunk musculature to sprint performance. Complementary evidence further indicates that trunk muscle cross-sectional area, including the rectus abdominis and iliacus, may contribute substantially to high-intensity performance tasks, explaining a large proportion of variance in jump distance [17]. In that study, a change-point regression analysis further suggested a non-linear relationship, with sprint time decreasing as transversus abdominis thickness increased up to a specific threshold, beyond which performance gains plateaued. These findings suggest that deep anterior trunk morphology may be relevant to sprint capacity, although the relationship may not be strictly linear across all levels of muscular development.

Furthermore, greater trunk musculature thickness has been associated with reduced trunk motion during unanticipated change-of-direction tasks in field-based athletes [16]. Specifically, dominant-side transversus abdominis thickness correlated significantly with both peak isometric trunk flexion torque (r = 0.55, p = 0.03) and reduced lateral trunk flexion during braking and propulsion phases. Moreover, total abdominal wall thickness was inversely correlated with 20 m sprint time (r = − 0.51, p = 0.05), further supporting the potential relevance of trunk muscle morphology for performance. In a complementary line of research, trunk muscularity, particularly the cross-sectional area of muscles such as the psoas major, has been shown to be significantly associated with initial sprint acceleration capacity [32].

Internal oblique in relation to sprint and agility performance

The internal oblique was also found to be associated with both sprint and agility performance. Although previous research has not consistently identified oblique musculature as a direct predictor of short-distance sprint velocity [32], evidence suggests that lateral abdominal wall morphology may nonetheless be functionally relevant. For instance, the cross-sectional area of the lateral abdominal wall has been reported to correlate strongly with 400-m sprint time and mechanical energy utilization efficiency [33]. Additionally, greater internal oblique thickness has been observed in trained runners compared to active and inactive individuals, suggesting potential sport-specific adaptation [34].

Recent evidence further highlights the functional importance of the internal oblique in trunk mechanics. The internal oblique has been shown to exhibit greater changes in thickness from rest to contraction compared to the external oblique, indicating a more prominent role in dynamic trunk stabilization [35]. Moreover, the orientation and mechanical contribution of the internal oblique allow it to play a dominant role in controlling rotational stiffness of the lumbar spine, contributing substantially to vertebral joint stability across multiple planes of motion [36]. Importantly, these functional roles extend beyond linear sprinting. During change-of-direction and turning movements, coordinated activation of the internal oblique and transversus abdominis has been shown to contribute to lumbopelvic stability and movement control strategies, which are essential for efficient directional transitions [37]. In this context, the internal oblique may be important for maintaining trunk stiffness and controlling rotational forces during multidirectional movements, which may help explain its association with change-of-direction performance.

With increasing sprint velocity, the trunk is subjected to elevated transverse-plane torsional demands and frontal-plane displacement forces [38, 39]. Excessive mediolateral trunk motion has been linked to reduced mechanical efficiency and greater non-forward-directed energy expenditure [40]. Trunk rotator muscles contribute substantially to the lumbopelvic axial moment responsible for limb forward acceleration [41], and stabilization of the sacroiliac joint during running relies on force closure generated by the transversus abdominis and internal oblique [42]. Electromyographic studies further demonstrate high activation levels of the internal oblique during rotational tasks [43] and coordinated trunk activation during sprinting [44].

Although muscle thickness does not directly reflect dynamic activation, greater internal oblique morphology may indicate enhanced force-generating capacity of the lateral abdominal wall. Collectively, these structural and functional findings may offer a plausible biomechanical rationale for the observed association between internal oblique thickness and both sprint and agility performance.

Bilateral symmetry of trunk muscles

Beyond performance associations, the present study also examined bilateral symmetry in trunk muscle morphology and found no significant side-to-side differences (ES < 0.2, trivial). This finding aligns with reports in youth and professional soccer players, where trunk and thigh muscle cross-sectional areas demonstrated minimal asymmetry (symmetry index ranging approximately between − 3% and + 2%, p > 0.05) [45]. Similarly, Idoate et al. [18] observed bilaterally balanced rectus abdominis development in professional soccer players despite greater overall muscle volume compared to non-athletes, suggesting that long-term soccer training may promote symmetrical trunk development.

Although some studies have reported side-to-side differences in abdominal musculature in athletic populations [19], such asymmetries have been interpreted as sport-specific adaptations rather than inherently pathological findings. Nevertheless, clinically relevant thresholds have been proposed; for example, an internal oblique thickness asymmetry exceeding 1.25 mm has been associated with increased risk of low back pain [46]. Collectively, these findings highlight that while symmetry appears preserved in trained soccer players, monitoring trunk muscle balance may remain important for both performance profiling and injury risk assessment.

Limitations

Despite these findings, several limitations should be acknowledged when interpreting the results. First, the relatively small sample size may limit the statistical stability of the analyses and restrict the generalizability of the results to broader football populations. Although an a priori power analysis suggested that this sample size was sufficient to detect moderate-to-large associations, larger samples are needed to confirm the robustness of these relationships. In addition, despite the use of Bonferroni correction to control for multiple comparisons, the combination of a small sample size and multiple statistical tests may still affect the stability of the observed associations. Additionally, due to the small sample size, potential confounding variables, such as body mass, height, or training status, were not controlled for in the analysis. Second, trunk muscle thickness was assessed at rest using ultrasound imaging. While ultrasound provides a reliable measure of muscle morphology, resting thickness does not necessarily reflect dynamic neuromuscular activation or stiffness during high-intensity movements such as sprinting. Future studies combining ultrasound with neuromuscular assessments, such as electromyography, may provide a more comprehensive understanding of trunk muscle function during athletic performance. Finally, the cross-sectional design of the present study precludes causal inference. Therefore, it cannot be determined whether greater deep trunk muscle thickness is linked to better sprint performance or whether faster athletes develop greater trunk musculature as a result of long-term training adaptations.

Practical implications

From a practical perspective, and considering the limitations of the present study, the findings suggest that greater thickness of specific deep anterior trunk muscles may be associated with sprint and agility performance in competitive football players. These findings may have practical implications for performance profiling, suggesting that monitoring trunk muscle thickness could provide additional insight into sprint and agility capabilities in football players. However, integrating morphological assessments with neuromuscular evaluations may further enhance the interpretation of trunk muscle function in applied settings.

Conclusion

The present study suggests that greater thickness of the transversus abdominis and internal oblique may be related to 20 m sprint and agility performance in competitive male football players after adjustment for multiple comparisons. These findings suggest that trunk muscle thickness may be related to sprint and agility performance in football contexts. No significant associations were observed between superficial trunk muscles and performance outcomes, and correlations with jump performance did not remain statistically significant after correction for multiple testing. Additionally, trunk muscle symmetry appeared to be well maintained in this cohort, consistent with previous findings in trained soccer players. However, given the cross-sectional nature of the study, these findings should be interpreted as associations rather than causal relationships. Further longitudinal and intervention-based studies are required to clarify the potential role of trunk musculature in performance.

Abbreviations

RA

Rectus abdominis

EO

External oblique

IO

Internal oblique

LM

Lumbar multifidus

TrA

Transversus abdominis

CMJ

Countermovement jump

Authors' contributions

F.S.C. and O.U. analysed and interpreted the data and were involved in writing the first draft of the manuscript. O.U., H.E.U., I.A.C., A.S.K., and F.S.C. made substantial contributions to the conception and design of the work, as well as writing and editing the manuscript’s final version. O.U., H.E.U., and F.S.C. contributed to data interpretation, writing, and editing of the manuscript’s final version. All authors read and approved the final manuscript.

Funding

No funding was received to assist with the preparation of this manuscript.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

All the procedures implemented in this study were approved by the Ethics Committee of the Inonu University, (approval number: 2024/4451). Informed consent forms were signed after the participants were informed of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.