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Functional independence of the transversus abdominis (TrA) from other trunk muscles for postural control is still unclear. This study aimed to clarify the specific function of the TrA to control standing posture by vibratory stimulation of the triceps surae. Fifteen men participated in this study. Muscle activity of the TrA, internal oblique, lumbar multifidus, gluteus maximus, rectus femoris, biceps femoris, gastrocnemius, and tibialis anterior was measured using fine-wire and surface electrodes. Participants were asked to maintain a quiet standing posture with and without vibration of the triceps surae, which induced a kinesthetic illusion and the concomitant backward sway of the body. The muscle activity of each muscle for 10 s was extracted with and without vibration. The muscle activity levels were compared between the conditions by a paired t-test or Wilcoxon signed-rank test. The activity of the TrA and rectus femoris was increased, whereas the internal oblique showed no change as a result of the induced kinesthetic illusion. In addition, the activity of the multifidus and biceps femoris was decreased. The TrA and rectus femoris could contribute to control the backward sway of the body. Furthermore, the TrA may have functional independence from the internal oblique during standing postural control. These results warrant further study in patients with low back pain. [ABSTRACT FROM AUTHOR]

Purpose: We previously reported that a Hammerobics exercise using weights can enhance trunk and lower extremity muscles, some studies suggested that training effects could also be expected without heavy weights. If the muscle activity induced by Hammerobics swinging with a 'light plastic ball' equals or surpasses that of the isometric static squat and synchronized squat with a heavy ball, this training approach could alleviate joint strain, fostering an exercise regimen universally accessible across generations, benefit for workouts sports and rehabilitation. Methods: Fifteen healthy men participated in this study. By using surface electromyography, muscle activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris long head, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured during a light Hammerobics synchronized squat (HSS-light), Hammerobics synchronized squat, and conventional isometric squat, and statistically compared. Results: The front-to-back tibialis anterior activity of HSS-light was significantly higher than that of conventional isometric squat. The activities of all other muscles, except for the multifidus, were not significantly different between these exercises in the front-to-back and back-to-front phases. Compared to the Hammerobics synchronized squat, the light Hammerobics synchronized squat showed no differences in front-to-back tibialis anterior, rectus femoris, biceps femoris long head, and internal oblique activities and back-to-front abductor hallucis, tibialis anterior, rectus femoris, and internal oblique activities. Conclusion: The HSS-light could stimulate muscles to the same level as the conventional isometric squat without weight bearing. While the HSS-light was less effective than the Hammerobics synchronized squat, there was no significant difference in internal oblique, rectus femoris, and tibialis anterior activities between these exercises. Hence, the HSS-light is an exercise method that can be viable approach to promoting accessible workouts sports and rehabilitation. [ABSTRACT FROM AUTHOR]

Background: Shoulder pain, known as swimmer's shoulder, is the most common injury for swimmers. Studies that have analyzed muscle activity have focused on the shoulder joint. However, the whole-body muscle coordination of swimmers with swimmer's shoulder is not clear, although swimming requires movements of the upper limbs, trunk, and lower limbs to obtain propulsive force. This study investigated differences in muscle coordination between swimmers with and without swimmer's shoulder during the front crawl and backstroke using muscle synergy analysis. Hypothesis: Swimmers with swimmer's shoulder have muscle synergies differing from those without it. Study Design: Case-control study. Level of Evidence: Level 4. Methods: A total of 20 elite swimmers who regularly swam front crawl and backstroke were included (swimmer's shoulder, n = 8; control, n = 12). Muscle synergy data were analyzed using the nonnegative matrix factorization method and compared between groups. Results: For both front crawl and backstroke, there were 2 synergies in the control group and 3 synergies in the swimmer's shoulder group. During recovery, the control group showed coordinated triceps brachii, serratus anterior, upper trapezius, lower trapezius, internal oblique, and external oblique muscles activities; however, in the swimmer's shoulder group, the contribution of the upper limbs decreased and only that of the trunk muscles increased. Conclusion: A comparison of muscle coordination during the front crawl and backstroke performed by swimmers with and without swimmer's shoulder revealed that coordination differed during the recovery phase. During both front crawl and backstroke, the swimmer's shoulder group could not maintain coordination with the upper limb when the trunk rolled, and split synergy was formed between the upper limbs and trunk. Clinical Relevance: Because coordination of the upper limbs and trunk is important during the recovery phase of front crawl and backstroke, swimmer's shoulder rehabilitation should introduce exercises to improve their coordination between the upper limbs and the trunk. [ABSTRACT FROM AUTHOR]

We aimed to evaluate the acute physiological effects of high‐load barbell back squat exercise on each lumbar intervertebral disk with varying squat depths. Thirteen subjects (age, 23.3 ± 3.5 years) performed parallel and half‐squat exercises (80% of one repetition maximum, eight repetitions, five sets) using a Smith machine. Sagittal magnetic resonance diffusion‐weighted and spin‐echo images of lumbar intervertebral disks were obtained by using a 1.5‐Tesla MR system before and after each squat exercise; apparent diffusion coefficient (ADC; an index of water movement) and T2 relaxation time (an index of water content level) of the nucleus pulposus were calculated at all lumbar intervertebral disks. Additionally, we measured the angles of lumbar lordosis and anterior pelvic tilt at the bottom position of each squat using a three‐dimensional motion‐capture system. The nucleus pulposus of L4/5 (−5.0%, P <.01) and L5/S1 (−6.6%, P <.01) intervertebral disks showed decreased ADC values after parallel squat exercise. Moreover, post‐exercise ADC value in parallel squat exercise was lower than that in half‐squat exercise at L5/S1 intervertebral disk (P <.05). In contrast, the nucleus pulposus of all lumbar intervertebral disks had no significant T2 change before and after both squat exercises. The angles of lumbar lordosis (P <.01) and anterior pelvic tilt (P <.01) were smaller in parallel squat than in half‐squat. Lower lumbar intervertebral disks are subject to greater mechanical stress during high‐load parallel back squat exercise, which may result from smaller lumbar lordosis and anterior pelvic tilt angles at the bottom position during parallel squat. [ABSTRACT FROM AUTHOR]

Context: The quadratus lumborum (QL) is expected to contribute to segmental motor control of the lumbar spine to prevent low back pain. It has different layers (anterior [QL-a] and posterior [QL-p] layers), whose functional differences are becoming apparent. However, the difference between the QL-a and QL-p activities during bridge exercises utilized in rehabilitation is unclear., Objective: To compare QL-a and QL-p activities during bridge exercises., Design: Repeated-measurement design was used to assess electromyographic activity of trunk muscles recorded during 14 types of bridge exercises., Setting: University laboratory., Participants: A total of 13 healthy men with no history of lumbar spine disorders participated., Intervention: The participants performed 14 types of bridge exercises (3, 3, and 8 types of side bridge, back bridge, and front bridge [FB], respectively)., Main Outcome Measures: Fine-wire electromyography was used for QL-a and QL-p activity measurements during bridge exercises., Results: Both QL-a and QL-p showed the highest activity during the side bridge with hip abduction  (47.3% [29.5%] and 43.0% [32.9%] maximal voluntary isometric contraction, respectively). The activity of the QL-a was significantly higher than that of the QL-p during back bridge with ipsilateral leg lift and FB elbow-toe with ipsilateral arm and contralateral leg lift (P < .05). With regard to the QL-p, the activity of the FB hand-knee with contralateral arm and ipsilateral leg lift, the FB elbow-knee with contralateral arm and ipsilateral leg lift, and the FB elbow-toe with contralateral arm and ipsilateral leg lift were significantly higher than that of the FB elbow-knee and FB elbow-toe (P < .05)., Conclusion: This study indicates different regional activities; the QL-a activated during the back bridge with ipsilateral leg lift and FB with ipsilateral arm lift, and the QL-p activated during the FB with ipsilateral leg lift. These results have implications for the rehabilitation of low back pain or lumbar scoliosis patients based on QL recruitment.