Comparative Analysis of Thoracic Rotation Exercises: Range of Motion Improvement in Standing and Quadruped Variants.

There have been few investigations into the effectiveness of thoracic spine exercises for improving thoracic range of motion (ROM) in any plane. This study assessed the effectiveness of two thoracic spine exercises: one in the quadruped position and one in the thoracic standing position. We determined how these exercises affect thoracic spine mobility ROM over a 2-week intervention period. Thirty-nine healthy participants were enrolled and assigned to a Quadruped Thoracic Rotation group (n=17 participants: 9 females and 8 males) or Flamenco Thoracic Spine Rotation group (n=22: 14 females and 8 males). All participants were administered a KOJI AWARENESSTM screening test, and the initial thoracic spine ROM before intervention exercise was measured in a laboratory setting. Quadruped Thoracic Rotation was performed as the quadruped exercise and Flamenco Thoracic Spine Rotation as the standing exercise. The KOJI AWARENESSTM thoracic spine test and ROM were evaluated on the day after the first exercise session and again after the program. Despite their different approaches to thoracic mobility, the quadruped exercise and standing exercise achieved equivalent improvement in thoracic ROM after 2 weeks. Practitioners have a range of exercise options for enhancing thoracic mobility based on their environmental or task-specific needs.

Sacroiliac joint pain increases repositioning error during active straight leg-raising.

PURPOSE: This study aimed to compare the repositioning error (RE) of patients with unilateral sacroiliac joint pain (SIJP) to that of patients with low back pain (LBP) and a healthy control (HC) group. Differences between the symptomatic and asymptomatic sides were also investigated. METHODS: Sixty-six patients with SIJP, LBP, and HC were included in this study. An active straight leg-raising repositioning test (ASLR-Rt) was performed. ASLR was performed three times each on the left and right sides, targeting a set base angle. RE was calculated as the difference between the base angle and the participant's attempt to adjust the target angle. RE was expressed as constant error (CE) and absolute error (AE). RESULTS: The CE of the SIJP group (median [interquartile range]) (6.9 [4.6‒10.4]) was significantly higher than that in the LBP group (3.2 [1.3‒7.1]) and the HC group (2.7 [0.3‒4.6]) (P = 0.009, d = 0.91, P < 0.001, d = 1.30). The AE of the SIJP group (7.3[5.0‒10.4]) was also significantly higher than that in the LBP (3.7[2.8‒7.1]) and HC groups (3.0[1.9‒4.2]) (P = 0.003, d = 1.04; P = 0.001, d = 1.57). Comparing the symptomatic and asymptomatic sides in the SIJP group, the symptomatic side (8.0[6.0‒10.6]) was significantly higher than the asymptomatic side (5.7[3.6‒8.1]) in terms of CE (P = 0.05, d = 0.51). CONCLUSION: Patients with SIJP increased RE during ASLR, which may be related to impaired proprioception and decreased motor control.

Hypomobility in Males and Hypermobility in Females are Risk Factors for Shoulder Pain Among Young Swimmers.

CONTEXT: The range of shoulder rotation is associated with shoulder pain in young male and female swimmers. However, the association between shoulder pain and shoulder complex mobility of the scapulothoracic and acromioclavicular joints has not yet been examined. Moreover, shoulder pain occurs more frequently in females than in males, but only a few studies have examined the relationship between shoulder pain and sex as a risk factor. This study aims to determine the association between shoulder complex mobility and shoulder pain in young male and female swimmers. DESIGN: Prospective cohort design. METHODS: The participants were competitive swimmers (n = 76; 37 males and 39 females) with a mean age of 14 years in Japan. The shoulder rotation width, which was the index of shoulder complex mobility, shoulder internal and external rotation range, and middle finger distance of the back-scratch test were measured. An examiner regularly visited the swimming clubs to evaluate the development of shoulder pain and swimming distance. Logistic regression analysis was used to determine the physical characteristics related to the overall development of shoulder pain in both female and male swimmers. The cutoff value was calculated using receiver operating characteristic curves. RESULTS: Sixteen participants, composed of 8 males and 8 females, developed shoulder pain. The overall swimming distance of the male (odds ratio [OR]: 1.0007, P = .01) and female (OR: 1.0018, P = .02) swimmers and the shoulder rotation width of the male (OR: 1.0952, P = .04) and female (OR: 0.888, P = .03) swimmers were identified as risk factors for shoulder pain. The cutoff value for swimming distance was 6000 m. Shoulder rotation width was more than 88 cm in males and <54 cm in females. CONCLUSIONS: Hypomobility and hypermobility of the shoulder complex were identified as risk factors for shoulder pain in male and female swimmers, respectively.

Acute effects of varying squat depths on lumbar intervertebral disks during high-load barbell back squat exercise.

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.

Comparison of Lumbar Kinematics with a History of Low Back Pain During Baseball Hitting.

The purpose of this study was to examine the influence of a history of low back pain (LBP) on pelvic and lumbar kinematics during baseball hitting. Twenty collegiate male baseball players (age, 21±1 years; height, 172.8±4.7 cm; weight, 72.7±6.2 kg; baseball experience, 13±1 years) performed 5 bat swings. Participants were categorized into the LBP group (n=10) or control group (n=10) based on having experienced lumbar spine pain due to bat swing that lasted more than 24 h within the last 12 months. Three-dimensional kinematic data of the pelvis and lumbar spine during bat swing were measured. Two-way ANOVAs were used to compare pelvic and lumbar kinematics throughout the bat swing between groups, and independent t-tests were used to compare the other outcomes between groups. There was a significant main effect between groups in lumbar flexion angle throughout the bat swing (p=0.047). The mean lumbar flexion angle of the LBP group throughout the bat swing was less than that of the control group. Additionally, the peak angular velocity of lumbar flexion of the LBP group was significantly faster than that of control group (p=0.047). These results can be helpful for longitudinal studies that identify the risk factors of LBP due to bat swing.

Change in Regional Activity of the Quadratus Lumborum During Bridge Exercises.

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.

Shoulder and elbow pain in junior high school baseball players: Results of a nationwide survey.

BACKGROUND: Despite proposals and guidelines to prevent baseball injuries in young players by societies and organizations, many shoulder and elbow injuries continue to occur among junior high school baseball players. In order to investigate the training conditions of junior high school baseball players and the risk factors for shoulder and elbow pain in the players, we conducted a questionnaire survey among junior high school baseball players throughout the country. METHODS: The questionnaire survey was conducted among junior high school baseball players in September 2016. RESULTS: A total of 11,134 junior high school baseball players belonging to 495 teams responded to the survey. Among these, 4004 players trained every day of the week and 1151 players played baseball games every month with no off-season. Among 9752 players who did not have shoulder and/or elbow pain in the spring and summer of 2015, 19.2% of players experienced elbow pain over the course of one year, 13.6% of players experienced shoulder pain, and 28.0% complained of shoulder and/or elbow pain. The frequency of elbow pain was more than that of shoulder pain. At risk for shoulder pain were pitchers and catchers and second-year students, while risk factors for elbow pain were playing pitcher and catcher positions, pitching or throwing ≥300 balls per week, playing ≥10 games on average per month and being left-handed. CONCLUSION: Risk factors for shoulder pain were different from those for elbow pain. To prevent elbow pain, coaches should pay attention to pitchers and catchers and left-handed players and not allow players to pitch or throw ≥300 full-power balls per week or participate in ≥10 games per month. They should also pay attention to pitchers and catchers and second-year students to prevent shoulder pain. It is important for coaches to train multiple pitchers and catchers.

A Trunk Stabilization Exercise Warm-up May Reduce Ankle Injuries in Junior Soccer Players.

The aim of this study was to investigate the efficacy of a trunk stabilization exercise warm-up program in reducing the incidence of lower extremity injuries among male junior soccer players. Two junior soccer teams participated in this study. The intervention (INT) team performed three trunk stabilization exercises before practice sessions and games, while a control (CON) team performed their usual warm-up without trunk exercises. Both teams engaged in regular soccer training and games, and were followed for the incidence of injury. As a result, overall injury incidence rates (IRs) were 2.65 injuries/1,000 h and 4.94 injuries/1,000 h in the INT and CON teams, respectively (incidence rate ratio [IRR]=0.54, 95% confidence interval [CI]=0.32-0.89, p=0.013). The IR of acute injuries was significantly lower in the INT team (1.91 injuries/1,000 h) than in the CON team (4.06 injuries/1,000 h) (IRR=0.47, 95%CI=0.26-0.84, p=0.009). Regarding injury sites, the IRs of ankle injuries in the INT team (0.32 injuries/1,000 h) were significantly lower than that in the CON team (2.28 injuries/1,000 h) (IRR=0.14, 95%CI=0.04-0.47, p<0.001). These results suggest that a warm-up program comprising trunk stabilization exercises alone can prevent acute injuries, especially ankle injuries.

Lumbar lordosis angle and trunk and lower-limb electromyographic activity comparison in hip neutral position and external rotation during back squats.

[Purpose] To compare the lumbar lordosis angle and electromyographic activities of the trunk and lower-limb muscles in the hip neutral position and external rotation during back squats. [Subjects and Methods] Ten healthy males without severe low back pain or lower-limb injury participated in this study. The lumbar lordosis angle and electromyographic activities were measured using three-dimensional motion-capture systems and surface electrodes during four back squats: parallel back squats in the hip neutral position and external rotation and full back squats in the hip neutral position and external rotation. A paired t-test was used to compare parallel and full back squats measurements in the hip neutral position and external rotation, respectively. [Results] During parallel back squats, the average lumbar lordosis angle was significantly larger in hip external rotation than in the hip neutral position. During full back squats, lumbar erector spinae and multifidus activities were significantly lower in hip external rotation than in the hip neutral position, whereas gluteus maximus activity was significantly higher in hip external rotation than in the hip neutral position. [Conclusion] The back squat in hip external rotation induced improvement of lumbar kyphosis, an increasing of the gluteus maximus activity and a decrease of both lumbar erector spinae and multifidus activities.

Piriformis electromyography activity during prone and side-lying hip joint movement.

[Purpose] To measure electromyographic activity of the piriformis using fine-wire electrodes during 7 hip movements. [Subjects and Methods] Eleven healthy men, without severe low back pain or lower limb injury, participated in this study. Fine-wire electrodes were inserted into the piriformis and surface electrodes were attached to the muscles in the hip region and the trunk muscles on the dominant arm side. Electromyographic signal amplitude was measured during 7 hip movements: side-lying external rotation in hip neutral position, side-lying abduction in hip neutral position, side-lying abduction in hip external rotation, side-lying abduction in hip internal rotation, prone extension in hip neutral position, prone extension in hip external rotation, and prone extension in hip internal rotation. Repeated-measures one-way analysis of variance was used to examine electromyographic activity in each of the 7 hip movements. [Results] Piriformis electromyographic activity was highest during prone hip extension in external rotation. Both the superior and inferior portions of the gluteus maximus were also highly activated during prone hip extension in external rotation. [Conclusion] Prone hip extension in external rotation induced high electromyographic activity in the piriformis and superior and inferior gluteus maximus muscles.

Comparison of muscle synergies before and after 10 minutes of running.

[Purpose] The purpose of this study was to investigate the modular control of locomotor tasks and compared the modules before and after a running intervention. [Subjects and Methods] Electromyographic measurements were performed on eight young, healthy males engaged in a 60s run on a treadmill at 2.8 m/s before and immediately after the 600s of running intervention. Electromyographic data for 15 trunk and lower-limb muscles on the right side were recorded. Muscle synergies were extracted from the electromyography signals using non-negative matrix factorization. [Results] Four modules explained the electromyographic activity of all muscles and had the functions of load acceptance (module 1), push-off (module 2), preparation of landing (module 3), and trunk-stabilization activity during the stance phase (module 4). Modules 1, 2, and 3 matched the basic modules reported in previous studies; whereas, module 4 was different before and after the intervention. [Conclusion] Before the intervention, module 4 engaged the trunk muscles and it was activated in the stance phase during running. However, after the intervention, module 4 engaged the muscles around the pelvis and it was activated after landing. This result suggests that the posture control changes from the trunk muscles to the lower-limb muscles after 10 minutes running.

Calf muscle activity alteration with foot orthoses insertion during walking measured by fine-wire electromyography.

[Purpose] The purpose of the study was to assess the muscle activity change of the tibialis posterior, flexor digitorum longus, and peroneus longus during gait with orthoses. [Subjects and Methods] Sixteen healthy males participated in this study. Activity of each muscle was measured by using fine-wire and surface electromyography. Gait task was performed by the participants barefoot, with footwear and with orthoses. The electromyography data from a stance phase of each gait trial were used for analysis. The stance phase was divided into contact, midstance, and propulsion phases. The data from ten participants were extracted for final analysis, as electromyography measurements were unsuccessful for the other six. [Results] The results demonstrated that orthoses significantly reduced the tibialis posterior muscle activity in the propulsion phase compared to that in the barefoot condition. Although there was a significant difference in the midstance phase, post hoc analysis did not indicate significant differences among the phases. No significant electromyography amplitude change was detected in flexor digitorum longus and peroneus longus. [Conclusion] Orthothes reduced the tibialis posterior activity level during gait. This result may be beneficial for patients with injuries related to excessive activity of tibialis posterior.

Critical factors for the prevention of low back pain in elite junior divers.

BACKGROUND/AIM: During competitive diving, divers jump up from 1 to 3 m springboards or 5 to 10 m platforms and dive into the water. The impact forces are very large in the water entry phase, and, as such, microtraumatic injuries are common due to the tremendous physical stress placed on the diver. Low-back pain (LBP) is the most frequently reported symptom in divers. This study aimed to extract possible risk factors related to LBP from physical and technical characteristics in Japanese elite junior divers. METHODS: Eighty-three elite junior divers (42 men and 41 women) in Japan were included in this study. LBP was assessed by a questionnaire, interview and physical examination during a national training camp. Morphological data, physical fitness and diving skills were also evaluated. The factors related to LBP were extracted by using logistic-regression analysis and the forward-selection method (likelihood ratio). RESULTS: A total of 37.3% (31 reports) of back pain occurred in the lumbar region. Shoulder flexibility (OR 0.919; 95% CI 0.851 to 0.992) and age (OR 0.441; 95% CI 0.239 to 0.814) were recognised as factors related to LBP in male-elite junior divers, whereas only age (OR 0.536; 95% CI 0.335 to 0.856) was a factor in female-elite junior divers. CONCLUSIONS: Our results suggest that shoulder flexibility is important for preventing LBP in elite-male junior divers, since they require full shoulder flexion during the water entry phase. Limited shoulder flexibility could cause lumbar hyperextension when adjusting for the angle of water entry.

Spino-pelvic-rhythm with forward trunk bending in normal subjects without low back pain.

A strong correlation between low back pain and tight hamstrings has been reported. However, the effect of tight hamstrings on spinal biomechanics remains unclear. The purpose of the study was to investigate spino-pelvic-rhythm during forward bending of the trunk and to clarify the rhythm features with regard to hamstrings tightness. Eighteen healthy male adults with no history of low back pain volunteered to participate. First, we measured the finger-to-floor distance (FFD) in the upright position and set this parameter to 100 %. Using a spinal mouse, spinal alignment was measured in the following four positions: (1) upright posture­100 % FFD; (2) forward bending­50 % FFD; (3) forward bending­25 % FFD; and (4) forward bending­0 % FFD (fingers in contact with the floor). Changes of the angle of the thoracic and lumbar spine as well as the pelvis were calculated. As an indicator of tight hamstrings, we measured straight leg raising (SLR) angle. From positions 1­2 (phase I), the entire spino-pelvic angle moved in 104°. During this phase, the lumbar spine mainly moved. In the second phase (positions 2­3), it moved in 16°. Interestingly, all but 2 subjects showed a negative angle in the thoracic motion, meaning that the thoracic spine extended 4° during trunk flexion, thus exhibiting paradoxical motion. During this phase, lumbopelvic rhythm showed 2 patterns. In 7 subjects, pelvic motion was greater than lumbar motion, while the remaining subjects showed the opposite. In subjects without tight hamstrings, 83 % showed a pelvis-dominant pattern. Only 7 subjects were capable of position 4. During this phase, only slight motion was noted in the spine, and the majority of the motion occurred in the pelvis. Lumbar and pelvic motion correlated negatively in all phases. SLR angle and pelvic motion correlated strongly during phase III, indicating dominant pelvic movement in flexible subjects. The lumbo-pelvic-rhythm comprises 2 patterns­lumbar dominant and pelvis dominant. In flexible subjects, pelvis movement was dominant. In conclusion, improving tight hamstrings may reduce lumbar loading thereby reducing low back pain.

Spino-pelvic-rhythm with forward trunk bending in normal subjects without low back pain.

A strong correlation between low back pain and tight hamstrings has been reported. However, the effect of tight hamstrings on spinal biomechanics remains unclear. The purpose of the study was to investigate spino-pelvic-rhythm during forward bending of the trunk and to clarify the rhythm features with regard to hamstrings tightness. Eighteen healthy male adults with no history of low back pain volunteered to participate. First, we measured the finger-to-floor distance (FFD) in the upright position and set this parameter to 100 %. Using a spinal mouse, spinal alignment was measured in the following four positions: (1) upright posture-100 % FFD; (2) forward bending-50 % FFD; (3) forward bending-25 % FFD; and (4) forward bending-0 % FFD (fingers in contact with the floor). Changes of the angle of the thoracic and lumbar spine as well as the pelvis were calculated. As an indicator of tight hamstrings, we measured straight leg raising (SLR) angle. From positions 1-2 (phase I), the entire spino-pelvic angle moved in 104°. During this phase, the lumbar spine mainly moved. In the second phase (positions 2-3), it moved in 16°. Interestingly, all but 2 subjects showed a negative angle in the thoracic motion, meaning that the thoracic spine extended 4° during trunk flexion, thus exhibiting paradoxical motion. During this phase, lumbopelvic rhythm showed 2 patterns. In 7 subjects, pelvic motion was greater than lumbar motion, while the remaining subjects showed the opposite. In subjects without tight hamstrings, 83 % showed a pelvis-dominant pattern. Only 7 subjects were capable of position 4. During this phase, only slight motion was noted in the spine, and the majority of the motion occurred in the pelvis. Lumbar and pelvic motion correlated negatively in all phases. SLR angle and pelvic motion correlated strongly during phase III, indicating dominant pelvic movement in flexible subjects. The lumbo-pelvic-rhythm comprises 2 patterns-lumbar dominant and pelvis dominant. In flexible subjects, pelvis movement was dominant. In conclusion, improving tight hamstrings may reduce lumbar loading thereby reducing low back pain.

Comparison of Muscle Coordination During Front Crawl and Backstroke With and Without Swimmer's Shoulder Pain.

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.

Specific Contribution of the Transversus Abdominis for Postural Control Against Perturbation Caused by Kinesthetic Illusion.

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.

Does scapular dysfunction alter scapular muscles activity and kinematics during swim stroke motion on adolescent swimmers?

Scapular dyskinesis (SD) indicates dysfunction of the scapular muscle activity during the arm elevation, resulting in altered scapular kinematics. This study examined whether SD alters scapular muscle activity and kinematics during swim stroke motion. Seventeen swimmers (mean age: 13 ± 1 years) were divided into SD (n = 8) and control (n = 9) groups. Scapular muscle activity (the upper, middle, and lower trapezius and the serratus anterior muscle) and kinematics data were collected and time-normalised (0-100%) during swim stroke motion by swim-bench on land. Scapular kinematics were calculated for upward rotation, internal rotation, posterior tilt, and arm elevation angles. To compare patterns of muscle activity and kinematics with and without SD, statistical parametric mapping unpaired t-test was used. The scapular upward rotation angle was decreased in SD compared to control in the 0-10% of the swim stroke phase (p = 0.041, t* = 3.018), and the internal rotation angle was increased in 0-15% of the phase (p = 0.033, t* = 2.994). Scapular posterior tilt and muscle activity showed no significant differences. These results suggested that SD altered scapular upward rotation and internal rotation at the initial phase of the swim stroke motion in adolescent swimmers and might potentially provoke a risk of subacromial impingement.

External focus instruction using a paper balloon: impact on trunk and lower extremity muscle activity in isometric single-leg stance for healthy males.

Introduction: Core stability is crucial for preventing and rehabilitating lumbar spine injuries. An external focus instruction using a paper balloon is an effective way to activate the trunk muscles. However, the degree of trunk and lower extremity muscle activation during single leg stance with external focus instruction using a paper balloon is unknown. This study aimed to investigate the core muscle involving activity in the trunk and lower extremities on both the support and non-support sides with or without using external focus instruction using a paper balloon during isometric single-leg stance. Methods: Thirteen healthy males aged 20-28 years volunteered to take part in this study and performed a single leg stance task with and without an external focus instruction, pressing their non-supporting foot onto a paper balloon without crushing it. The participant's muscle electrical activity was recorded during the single leg task using surface EMG and intramuscular EMG for six trunk muscles (transversus abdominis, internal oblique, external oblique, rectus abdominis, multifidus, and lumbar erector spinae) and five lower extremity muscles (gluteus maximus, gluteus medius, adductor longus, rectus femoris, and biceps femoris). Results: Compared to the normal single leg stance, the external focus instruction task using a paper balloon showed significantly increased transversus abdominis (p < 0.001, p < 0.001), internal oblique (p = 0.001, p < 0.001), external oblique (p = 0.002, p = 0.001), rectus abdominal (p < 0.001, p < 0.001), lumbar multifidus (p = 0.001, p < 0.001), lumbar erector spinae (p < 0.001, p = 0.001), adductor longus (p < 0.001, p < 0.001), rectus femoris (p < 0.001, p < 0.001), and biceps femoris (p < 0.010, p < 0.001) muscle activity on the support and non-support sides. Conclusion: In conclusion, external focus instruction using a paper balloon significantly activates the trunk and lower extremities muscles on both the support and non-support sides. This finding provides insights for designing programs to improve coordination and balance. The benefits extend to diverse individuals, encompassing athletes, tactical professionals, and the general population, mitigating the risk of injury or falls linked to inadequate lower limb balance.

Entry phase in men's backward dive pike: association between the shoulder joint and trunk angles.

BACKGROUND: A high prevalence of lower back pain has been observed in competitive divers. Hyperextension of the lumbar vertebrae during water entry is considered the main mechanism behind the incidence of lower back pain in divers. Therefore, this study aimed to investigate the influence of the shoulder angle on the entry alignment. METHODS: Posture angles of 13 male drivers (age: 16.8±2.9 years) who were invited to the national training camp in 2012 by Japan Swimming were recorded at the time of water entry via 201B using a high-speed camera. RESULTS: A negative correlation was observed between shoulder joint flexion and trunk extension angles on water entry. In addition, the trunk angle was significantly different between groups. For the lower back pain group, 210.4±5.7°, and in the non-lower back pain group, 199.9±9.0°, angles were observed with a larger extension of the trunk on water entry in the lower back pain group. CONCLUSIONS: The alignment on water entry was associated with the occurrence of lower back pain. Which suggested that enough shoulder flexibility can prevent the incidence of lower back pain.