Background The strength and size of core muscles, including the abdominal muscles, are crucial to proper function in most activities. Therefore, it is important to reliably assess these characteristics. Our primary objective was to determine if the length, thickness and cross-sectional area of the transversus abdominis (TrA) can be visualized independently from the internal and external abdominal oblique muscles using extended field of view ultrasound imaging at rest and with contraction and to establish its intra- and inter-tester reliability. Methods Twenty-six individuals were recruited to participate in the study (20 F, 6 M), average age 24.0 years (SD 9.4), height 170.7 cm (SD 8.6) and weight 63.9 kg (SD 9.0). From this total number of participants, two groups of 16 randomly selected participants were assessed to determine intra- and inter-tester reliability respectively. Extended field of view ultrasound images were obtained at three vertebral levels during rest and contraction in the side lying position for both the right and left sides of the trunk. Results Excellent intra-tester and inter-tester reliability was seen (ICC range of 0.972 to 0.984). The overall average percent standard error of the measurement for all measurements and locations was approximately 4%. The overall average minimal difference for the thickness measurement for the resting and contraction conditions combined were as follows: intratester 0.056 (0.014) cm and intertester 0.054 (0.017) cm, for area intratester 0.287 (0.086) cm2 and intertester 0.289 (0.101) cm2 and for length intratester 0.519 (0.097) cm and intertester 0.507 (0.085) cm. Conclusions Extended field of view ultrasound imaging is an effective method of reliably capturing clear images of the TrA during rest and contraction. It provides an efficient mechanism for the analysis of muscle morphology by being able to measure the cross-sectional area, thickness, and length on one image. This methodology is recommended for studies investigating TrA function and training.

BackgroundMuscle function may be impaired in people with generalised hypermobility, yet prior studies have primarily focused on muscles within the extremities. We aimed to examine changes in lateral abdominal muscle (transversus abdominis (TrA) and the external (EO) and internal abdominal obliques (IO)) thickness and length during contraction between participants with and without hypermobility.MethodsThis cross-sectional study examined 12 participants with hypermobility and 12 age-matched, sex-matched, height-matched and weight-matched participants without hypermobility. The Beighton and Belavy-Owen-Mitchell score assessed systemic hypermobility. Muscle thickness and length were measured via panoramic ultrasound scans at rest and during contraction.ResultsWhen compared with rest across all lumbar levels (L1–L5), contraction produced a lesser increase in TrA thickness (β=0.03, p=0.034) for participants with hypermobility compared with control. No group-by-condition interaction was observed for TrA length across all lumbar levels (L1–L5; p=0.269). Contraction produced a greater decrease in EO thickness (β=0.08, p=0.002) at L3 only for participants with hypermobility compared with control. No group-by-condition interactions were observed for IO thickness.ConclusionParticipants with hypermobility had partially impaired lateral abdominal muscle function given a lesser ability to increase TrA muscle thickness during contraction compared with controls.

Background: The strength and size of core muscles, including the abdominal muscles, are crucial to proper function in most activities. Therefore, it is important to reliably assess these characteristics. Our primary objective was to determine if the length, thickness and cross-sectional area of the transversus abdominis (TrA) can be visualized independently from the internal and external abdominal oblique muscles using extended field of view ultrasound imaging at rest and with contraction and to establish its intra- and inter-tester reliability. Methods: Twenty-six individuals were recruited to participate in the study (20 F, 6 M), average age 24.0 years (SD 9.4), height 170.7 cm (SD 8.6) and weight 63.9 kg (SD 9.0). From this total number of participants, two groups of 16 randomly selected participants were assessed to determine intra- and inter-tester reliability respectively. Extended field of view ultrasound images were obtained at three vertebral levels during rest and contraction in the side lying position for both the right and left sides of the trunk. Results: Excellent intra-tester and inter-tester reliability was seen (ICC range of 0.972 to 0.984). The overall average percent SEM for all measurements and locations was approximately 4%. The overall average minimal difference for the thickness measurement for the resting and contraction conditions combined were as follows: intratester 0.056 (0.014) cm and intertester 0.054 (0.017) cm, for area intratester 0.287 (0.086) cm2 and intertester 0.289 (0.101) cm2 and for length intratester 0.519 (0.097) cm and intertester 0.507 (0.085) cm. Conclusions: Extended field of view ultrasound imaging is an effective method of reliably capturing clear images of the TrA during rest and contraction. It provides an efficient mechanism for the analysis of TrA morphology by being able to measure the cross-sectional area, thickness, and length on one image. This methodology is recommended for studies investigating TrA function and training.

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Background: Emerging evidence suggests that muscle function can be impaired in people with generalized hypermobility. The Beighton scale was developed to assess for the presence of hypermobility. This cross-sectional study assessed the activation of the lateral abdominal muscles in hypermobile (N=10; Beighton score >5) and matched non-hypermobile control (N=10) participants. Methods: Panoramic ultrasound scans of the transversus abdominis (TrA) and the external and internal abdominal obliques (EO and IO, respectively) were obtained at three lumbar levels (L1, L3, L5) at rest and during the hollowing maneuver. Results: Between-group differences in the TrA length, as well as TrA, EO and IO thickness changes between conditions (rest vs hollowing) and trunk strength and endurance were examined. Hypermobile participants exhibited less TrA shortening than controls (L1-L5: 5.1% difference, L3: 8.9% difference) and greater thickness changes at level L1 (12.7% difference). EO and IO thickness differed between groups for both conditions, where both of the muscles were 0.07cm - 0.18cm thicker at rest and 0.07cm - 0.19cm thicker with hollowing in the hypermobile participants compared to control (all: P<0.001). The ability to contract the EO was less in hypermobile participants compared to controls (P=0.002; -5.3% vs no change in thickness), while the ability to contract the IO was greater in hypermobile participants compared to in controls (P=0.038; +21.3% vs +17.6% thickness change). Hypermobile participants demonstrated over 30% greater average trunk flexion strength. Moreover, greater joint mobility was associated with less TrA muscle shortening, reduced EO thickness changes, greater isometric trunk muscle strength for both extension and flexion (all: P<0.001) and with reduced trunk muscle endurance for extension and flexion (P=0.006 and P=0.002, respectively). Conclusion: The results of this study indicate joint hypermobility is associated with reduced ability to contract TrA and EO, however, this did not appear to be associated with impaired function (e.g. muscle strength and endurance).