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BACKGROUND: External focus isometric exercises using a paper balloon can change trunk muscle activation in the chest squeeze; however, it is unknown whether this method affects muscle activities in conventional exercises. OBJECTIVE: To check variations of trunk muscle activity during front plank (static task) and shoulder press (dynamic task) both with and without instruction to avoid crushing an object. METHODS: Twenty-six healthy adult males aged 19–49 were recruited. Ten trunk muscle activities were measured using surface electromyography during a front plank and dynamic shoulder press exercises, both with and without external-focus instruction. RESULTS: Adding the external-focus using the paper balloon to the front plank significantly activated 8 out of the 10 muscles. In the downward shoulder press, 5 out of 10 muscles with 50% 1 RM, 2 out of 10 muscles with 100% 1 RM were significantly activated. CONCLUSIONS: Adding external-focus instruction using paper balloon increases trunk muscles in front plank and shoulder press while possibly improving trunk stability. Novel exercises using paper balloon may efficiently activate specific muscles without external loading thus possibly reducing the stress on the involved joints during exercise.

Draw-in is a promising intervention for regaining isolated control of the transverse abdominis (TrA). Exercises to stimulate isolated contractions are needed; however, the appropriate methods are unclear. The objectives of this study were to examine how the muscle activity and muscle activity ratio of abdominal muscles change with various verbal instructions and to determine the onset of the abdominal muscles during drawin. The participants were 21 healthy men. TrA electromyography was performed using fine-wire electrodes, and the internal oblique (IO), external oblique (EO), and rectus abdominis (RA) were determined using surface electrodes. The participants performed seven abdominal exercises according to verbal instructions and isolated voluntary contraction of the TrA for more than 5 sec. The TrA showed higher activity in bracing. IO and EO activities were highest in bracing, whereas RA showed the highest activity in maximum bracing. TrA/IO and TrA/EO were not significantly different between conditions. The results of the onset activity analysis of the abdominal muscles during the draw-in maneuver showed that the TrA was significantly earlier than the other muscles. The activity ratios of TrA to IO and EO were highly individualized and did not differ according to the verbal instruction. Maximum draw-in showed more significant IO activity, and bracing showed co-contraction of the superficial and deep abdominal muscles. During draw-in, the TrA initiated the earliest activity among the abdominal muscles and then isolated activity for 1.1 sec.

The aim of this study was to clarify the effects of transcutaneous vagus nerve stimulation (tVNS) to the left cymba concha on the pain perception using nociceptive withdrawal reflex (NWR), which is known to be associated with chronic pain, and to investigate whether tVNS-induced suppression of the NWR and parasympathetic activation is correlated. We applied either 3.0 mA, 100 Hz tVNS for 120 s in the left cymba concha (tVNS condition) or the left earlobe (Sham condition) for twenty healthy adults. NWR threshold was measured before (Baseline), immediately after (Post 0), 10 min (Post 10) and 30 min after (Post 30) stimulation. The NWR threshold was obtained from biceps femoris muscle by applying electrical stimulation to the sural nerve. During tVNS, electrocardiograph was recorded, and changes in autonomic nervous activity were analyzed. We found that the NWR thresholds at Post 10 and Post 30 increased compared to baseline in the tVNS group (10 min after: p = 0.048 30 min after: p = 0.037). In addition, increased parasympathetic activity by tVNS correlated with a greater increase in NWR threshold at Post 10 and Post 30 (Post 10: p = 0.01; Post 30: p = 0.005). The present results demonstrate the pain-suppressing effect of tVNS as assessed with NWR threshold and suggest that the degree of parasympathetic activation during tVNS may predict the effect of tVNS after its application.

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 Conclusions: Hypomobility and hypermobility of the shoulder complex were identified as risk factors for shoulder pain in male and female swimmers, respectively.

This study aimed to clarify the changes in the activity of the trunk and lower limb muscles during 2000-m rowing. Ten male rowers performed a 2000-m race simulation on a rowing ergometer. Electromyography results of the abdominal muscles, back muscles, gluteus maximus (GMax), biceps femoris (BF), and rectus femoris (RF) were recorded. The electromyographic activity during the three strokes after the start (initial stage), at 1000m (middle stage), and before the end (final stage) were analyzed. From the handle position, the rowing motion was divided into five phases (early-drive, middle-drive, late-drive, early-recovery, and late-recovery). The peak activities of the abdominal muscles, back muscles, GMax, and BF in each stroke of the rowing motion were delayed at the middle and final stages compared to the initial stage (P0.05). The peak activity of the RF was observed in the late-drive phase at the initial stage, whereas a high RF activity was observed in the middle-drive phase at the middle and final stages (P0.05). Considering the results of the activity of the back muscles and RF, RF muscular endurance enhancement may lead to a decrease in the load on the back muscles and help prevent muscular low back pain in rowers. J. Med. Invest. 69 : 45-50, February, 2022.

The purpose of this study was to determine changes in the mechanical properties of the thigh and lower leg musculature during the early follicular and ovulatory phases. Subjects were 15 female university students with normal menstrual cycles. The early follicular and ovulatory phases were estimated by the basal body temperature method, ovulation kits, and salivary estradiol concentration measurement. The MyotonPRO digital palpation device (Myoton AS, Tallinn, Estonia) was used to measure muscle and tendon stiffness in the early follicular and ovulatory phases. Measurement sites were the rectus femoris (RF), vastus medialis (VM), patellar tendon (PT), medial head of gastrocnemius, soleus, and Achilles tendon. No significant differences in stiffness of all muscle tendons were identified between the early follicular and ovulatory phases. In the ovulatory phase, a significant positive correlation was seen between stiffness of RF and PT, and between stiffness of VM and PT. These results suggest that the stiffness of muscles and tendons of anterior sites of the thigh and posterior sites of the lower leg may not change between the early follicular and ovulatory phases. During the ovulatory phase, tendons may also be stiffer in individuals with stiffer anterior thigh muscles.

This study investigated the relationship between changes in foot characteristics and sex differences during the menstrual cycle in healthy male and female university students. We examined 10 female subjects and 14 male subjects. The menstrual cycle was divided into the three phases: the early follicular phase, ovulatory phase, and luteal phase via basal body temperature, an ovulation kit, and salivary estradiol and progesterone concentration measurements. Foot characteristics required for the calculation of the arch height index (AHI) were measured using a three-dimensional foot scanner under conditions of 10% and 50% weight-bearing loads. Arch height at 50% of foot length and truncated foot length were measured, and AHI was calculated by dividing arch height by truncated foot length. Arch height flexibility (AHF) was defined as the change in arch height from 10% weight-bearing load to 50% weight-bearing load. AHI was significantly lower in females than in males in the early follicular and ovulatory phases but did not differ significantly between males and females in each phase. AHF did not differ significantly between males and females in each phase. AHI and AHF showed no periodic fluctuation, suggesting that sex differences in AHF may be absent.

This study aimed to clarify the differences in the onset of trunk muscle activity with and without anticipation of the movement starting time during rapid shoulder movements. Ten healthy men in a relaxed upright position performed rapid 135° flexion, 135° abduction, and 45° extension of the shoulder on the dominant hand side with and without anticipation of the movement starting time. They moved their shoulder joints following a 3-s countdown and a light stimulus in the anticipation and non-anticipation conditions, respectively. Electromyography of the anterior and posterior quadratus lumborum, transversus abdominis, internal oblique, external oblique, rectus abdominis, lumbar multifidus, lumbar erector spinae on the non-dominant hand side, and the middle deltoid on the dominant hand side were measured. The onset of activity of each trunk muscle relative to the onset of the middle deltoid was calculated. Two-way analysis of variance (eight trunk muscles × two anticipation conditions) was used to compare the onset of electromyographic activity of the trunk muscles in each direction of the shoulder movement. There were significant interactions between the muscles and anticipation conditions during shoulder abduction and extension. The onset of activity in the anterior and posterior quadratus lumborum, transversus abdominis, and internal oblique occurred earlier with anticipation of the movement starting time than without anticipation during shoulder abduction and extension. The anticipation of movement starting time may contribute to a reliable center of mass control within the support base and improve lumbar spine stability by hastening the onset of activity of the deep trunk muscles.

Background: Improvements in motor control of the scapular muscles are important for the prevention and rehabilitation of shoulder and elbow injuries in overhead athletes. Purpose: To clarify scapular muscle activity during multijoint compound movement exercises using fine-wire and surface electrodes. Study Design: Descriptive laboratory study. Methods: Sixteen healthy men performed 5 types of exercises (cat and dog, trunk rotation, A-exercise, T-exercise, and Y-exercise). Muscle activity was measured as percentage of maximum voluntary isometric contraction (%MVIC) by using fine-wire electrodes in the rhomboid major (Rhom) and using surface electrodes in the upper (UT), middle (MT), and lower (LT) trapezius and serratus anterior (SA) muscles. The Rhom/UT, MT/UT, LT/UT, and SA/UT muscle activity ratios were calculated. One-way analysis of variance was used to compare the %MVIC and muscle activity ratios between exercises. Results: There was no significant difference in Rhom activity between the exercises (34.6-54.2%MVIC; P = .25). LT activity was significantly greater in the trunk rotation (58.0 ± 24.6%MVIC) and Y-exercise (63.2 ± 40.1%MVIC) than in the cat and dog scapular retraction (19.6 ± 9.3%MVIC) and A-exercise (28.2 ± 14.2%MVIC) ( P < .05). SA activity was significantly greater in the cat and dog scapular protraction (26.7 ± 11.0%MVIC) and Y-exercise (25.6 ± 19.3%MVIC) than in the other exercises ( P < .05). The SA/UT activity ratio in the cat and dog scapular protraction exercise (9.64 ± 8.48) was significantly higher than in the other exercises ( P < .05). Conclusion: All the exercises were effective for activating the Rhom. The trunk rotation and Y-exercise were effective for activating the LT, and the cat and dog scapular protraction exercise was effective for activating the SA while suppressing the UT. Clinical Relevance: These results enable exercise selection based on muscle activity characteristics (moderate [20%-50%MVIC] and high [>50%MVIC] levels contribute to muscle activation) to prevent and rehabilitate shoulder and elbow injuries.

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.

Orthoses are often used for the treatment or prevention of injuries. The effect of orthoses on the activity of calf muscles such as the tibialis posterior (TP), flexor digitorum longus (FDL), and p...

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 P 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.

BACKGROUND: Perturbation exercises enhance lower limb and trunk muscles, and adding swing perturbation while loading during exercise might improve muscle activation or strength. OBJECTIVE: To check variations in trunk and lower limb muscle activity during conventional isometric squats, and whether it will change with or without swing using the Hammerobics-synchronized squat method.METHODS: Twelve healthy men participated in this study. Activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured using surface electromyography during a Hammerobics-synchronized squat and conventional isometric squat. Muscle activities were statistically compared between squat methods.RESULTS: Hammerobics-synchronized squats significantly activated the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, semitendinosus, and multifidus muscles, in both phases, compared with the conventional isometric squats. CONCLUSIONS: The Hammerobics-synchronized squat exercise can be considered for trunk and foot stability exercise.

Background Changes in trunk and hip muscles are believed to be important in subjects with nonspecific chronic low back pain (NSCLBP), but little is known about specific changes, or how they might be affected by core stabilization exercises. The aim of this study was to compare six key muscles before and after these exercises. Methods Thirty two NSCLBP patients were assigned randomly into two groups: exercise (n = 17) and control (n = 15). On 5 days per week for 4 weeks, the Exercise group performed 16 core stabilization exercises and the Control group received transcutaneous electrical nerve stimulation and a ‘hot-pack’. Surface electromyography (EMG) was used to assess maximum bilateral activity of transversus abdominis (TrA), multifidus (MF) and gluteus maximus (Gmax) muscles. Ultrasound imaging was used to measure the rest and contracted thickness of these muscles. Pain and disability were assessed using a visual analogue scale (VAS) and the Oswestry Disability Index. Results When left and right-side muscle data were combined, two-way ANOVAs showed a nonsignificant interaction effect for all dependent variables (P > 0.05), significant time effects on resting muscle thickness for TrA (P = 0.01), MF (P = 0.041) and Gmax (P = 0.003), EMG signals of TrA (P = 0.038), pain and disability (P = 0.000). There were a significant group effect on contracted thickness for TrA (P = 0.032) and Gmax (P = 0.026) and disability (P = 0.017). Conclusions Core stabilization exercises increased contracted thickness of TrA and Gmax muscles and decreased disability in subjects with NSCLBP.

Abnormal foot motion is considered to be related to sports related injuries. This study aimed to identify the relationship between calf muscle activity and inter-segment coordination of the foot during single-leg drop jumps. Eleven healthy men participated and performed single-leg drop jumps from a 30-cm box. Muscle activity of the tibialis posterior (TP), flexor digitorum longus, peroneus longus (PL) and gastrocnemius were measured. The rearfoot and midfoot segment angle from landing to leaping were calculated according to the Rizzoli Foot Model and time scaled to 100%. A modified vector coding technique was employed to classify inter-segment coordination of every 1% into four patterns (in-phase, anti-phase, rearfoot phase,and midfoot phase). The relationship between percentage of each pattern and muscle activity levels were statistically analysed with correlation coefficient. The TP showed a significant positive correlation with percentage of in-phase in coronal plane (

OBJECTIVE Pelvic tilt exercises are used clinically to correct lumbopelvic alignment. The anterior and posterior layers of the quadratus lumborum are important for pelvic motor control in the coronal plane. This study aimed to evaluate whether the anterior and posterior activity is related to the pelvic tilt angle during pelvic tilt exercises. DESIGN The study design was single-occasion repeated measures in a randomized manner. Twelve healthy men performed the four directions of the pelvic tilt exercises (anterior or posterior pelvic tilt and lateral pelvic elevation on the ipsilateral or contralateral measurement side). The electromyographies of the anterior and posterior were recorded using intramuscular fine-wire electrodes and normalized to isometric peak electromyography. RESULTS The activity of the anterior and posterior during lateral pelvic elevation on the ipsilateral measurement side (19.0 ± 16.0 percent of maximal voluntary isometric contraction) was significantly higher than that during other directions of the pelvic tilt exercises (P < 0.01). There was a significant positive correlation between the anterior activity and the maximum change angles of pelvic tilt during lateral pelvic elevation on the ipsilateral measurement side (r = 0.674, P = 0.016). CONCLUSIONS The anterior activity was related to a large lateral pelvic elevation angle on the ipsilateral side during pelvic tilt exercises.

Objective To identify injuries and physical characteristics affecting swimmers’ performance. Design Prospective study. Setting Laboratory-based. Participants Sixty-four Rio Olympic candidates (36 men, 28 women), who were high level swimmers ranked among the top 32 in the 2014 World Ranking in swimming. The participants were categorized into the Olympian group (n = 25), swimmers who were consecutively selected for the Olympic team, and the non-Olympian group (n = 39), swimmers who were not. Main outcome measures Four months prior to the Olympic qualification in 2016, an orthopedist and two physical therapists evaluated injuries and 11 physical characteristics of the swimmers. The prevalence of total overuse injuries, shoulder and low back injury, and physical characteristics were compared between the two groups. Results The female swimmers in the non-Olympian group had a 53.3% prevalence of total overuse injuries, which was significantly higher than that of those in the Olympian group with 15.4% (p = 0.037). The prevalence of total over use injuries in male swimmers in both the Olympian and non-Olympian groups was 41.7%. Female Olympian group showed that the shoulder external rotation range of motion was significantly less than that of non-Olympian group (97.8 ± 5.7 and 103.6 ± 7.3, p = 0.046). Conclusions In female swimmers, total overuse injuries four months before an important competition influence their performance at the event.

This study aimed to investigate whether muscle coordination differs between swimmers with and without a history of swimmer's shoulder (SS). Muscle synergies, which can assess muscle coordination, in young elite male swimmers were analyzed using surface electromyography (EMG). Twenty elite swimmers who swam the butterfly stroke were included in this study (SS n=8; control n=12). Four muscle synergies in both groups were identified. Synergy #1, which is involved in the early pull, and Synergy #3, which is involved in the early recovery, were shown to be different synergies in both groups. In the SS group, the contribution of the internal oblique, external oblique, and rectus abdominis, which are involved in stabilizing the trunk, was low during the early pull. In the early recovery, the SS group had lower contributions of the serratus anterior, upper trapezius, and lower trapezius involved in stabilizing the shoulder girdle, and a lower contribution of the erector spinae presenting in the control group. In the rehabilitation is desirable to introduce exercises to obtain coordination of the upper limb and abdominal muscles in the early pull phase, and coordination of the periscapular muscles and erector spinae in the early recovery phase.

Psychological pressure during sports competition disturbs the ideal physical movement and causes injury. Baseball batting frequently causes trunk injuries. This study aimed to examine the influence of psychological pressure on the lumbar kinematics and trunk muscle activity during the baseball batting. Fourteen collegiate baseball players participated in this study. The participants performed bat swings under three different psychological conditions (non-pressure, pressure, and emphasized pressure). The lumbar kinematics and trunk muscle activity were measured during each bat swing. One- and two-way analyses of variance were performed to compare the lumbar kinematics and trunk muscle activity among different psychological pressure conditions. The lumbar flexion angle throughout the bat swing in the swing phase, from the moment of ground contact of the lead foot to the moment of ball contact, was significantly larger under the pressure and emphasized pressure conditions than under the non-pressure condition (P

The purpose of this study was to clarify the influence of different postures on the activity of the shoulder girdle and lower back muscles while using a smartphone. Sixteen healthy male participants maintained two postures while using a smartphone : a good posture in which the tragus and acromion were closer to the vertical line passing through the greater trochanter, and a poor posture in which the tragus and acromion were farther from the vertical line passing through the greater trochanter. The target muscles were the rhomboid major (Rhom), upper trapezius, middle trapezius, lower trapezius (LT), lumbar erector spinae (LES), and lumbar multifidus (LMF). The activities of the Rhom and LT were significantly lower with poor posture than those with good posture. The activities of LES and LMF were significantly higher with poor posture than those with good posture. The results of this study indicated that poor posture was associated with hypoactivity of the shoulder girdle muscles and hyperactivity of the lower back muscles when compared with good posture. Poor posture for prolonged periods while using a smartphone would lead to malfunction of the shoulder girdle muscles and musculofascial lower back pain. J. Med. Invest. 67 : 274-279, August, 2020.

Background Medial tibial stress syndrome is a common sports related injury. Altered foot kinematics can be a risk factor for the injury. Since foot segments can move independently, intersegment coordination is important for proper foot function. This study aimed to compare the foot intersegmental coordination pattern and single segment kinematics between female lacrosse players with and without a history of medial tibial stress syndrome during drop jump. Methods Twelve players with a medial tibial stress syndrome history and 12 players with no history were enrolled. Foot kinematics, including angle at landing and peak angle and excursion at the rearfoot, midfoot, and forefoot during single-leg drop jumps were analysed. Each segment motion data from landing to leaping was time-scaled to 100% to analyse the intersegmental coordination with a modified vector coding technique. Instant intersegmental coordination of every 1% was classified into four patterns (in-phase, two segments rotate in the same direction with similar amplitudes; anti-phase, two segments rotate in opposite directions; proximal phase, proximal segment dominantly rotates in the same direction compared to the distal segment; and distal phase, distal segment dominantly rotates in the same direction compared to the proximal segment). The percentage of intersegmental coordination pattern and kinematics in each segment were compared between the groups using the Student’s t test. Results Groups with a history of medial stress syndrome showed a significantly higher percentage of proximal phase between the rearfoot and midfoot in the sagittal (Mean ± SD; history, 52.2 ± 17.9%, no history, 29.3 ± 16.7%; p = 0.004) and coronal planes (history, 40.3 ± 22.0%, no history, 15.9 ± 9.1%; p = 0.004). Dorsiflexion excursion (history, 34.5 ± 4.5°, no history, 29.6 ± 2.1°; p = 0.003) were significantly larger in a history of medial tibial stress syndrome group compared to no history group. Conclusions Rearfoot dominant motion pattern relative to the midfoot may be related to medial tibial stress syndrome. Intersegmental coordination analysis may be useful for detecting abnormal foot coordination patterns. Also, stabilization for the rearfoot may be required rather than the midfoot for intervention.

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.

The nordic hamstring exercise (NHE) is a dynamic lengthening hamstring exercise that requires trunk and hip muscles activation. Thigh muscles activation, specifically hamstring/quadriceps contractions has been previously examined during NHE. Trunk and hip muscles activity have not been enough studied. The aim of this study was to analyze of hip and trunk muscles activity during NHE. Surface electromyography (EMG) and kinematic data were collected during NHE. Ten healthy men with the age range of 21-36 years performed two sets of two repetitions with downward and upward motions each of NHE. EMG activity of fifteen trunk and hip muscles and knee kinematic data were collected. Muscle activity levels were calculated through repeated measure analysis of variance in downward and upward motions, through Paired t-test between downward and upward motions and gluteus maximus to erector spine activity ratio (Gmax/ES ratio) using Pearson correlation analyses were evaluated. Semitendinosus and biceps femoris muscles activity levels were the greatest in both motions and back extensors and internal oblique muscles activity were greater than other muscles (P

This study aimed to clarify the differences in electromyographic activity between the quadratus lumborum anterior (QL-a) and posterior layers (QL-p), and the relationship among trunk muscles and gluteus medius (GMed) activities during forward landing. Thirteen healthy men performed double-leg and single-leg (ipsilateral or contralateral sides as the electromyography measurement of trunk muscles) forward landings from a 30 cm-height-box. The onset of electromyographic activity in pre-landing and the electromyographic amplitude of the unilateral QL-a, QL-p, abdominal muscles, lumbar multifidus (LMF), erector spinae (LES), and bilateral GMed were recorded. Two-way ANOVA was used to compare the onset of electromyographic activity (3 landing leg conditions × 10 muscles) and electromyographic amplitude among (3 landing leg conditions × 2 phases). The onset of QL-p was significantly earlier in contralateral-leg landing than in the double-leg and ipsilateral-leg landings. The onset of LMF and LES was significantly earlier than that of the abdominal muscles in contralateral-leg landing. QL-p activity and GMed activity on the contralateral leg side in the pre-landing were significantly higher in contralateral-leg landing than in the other leg landings. To prepare for pelvic and trunk movements after ground contact, LMF, LES, QL-p on non-support leg side, and GMed on support leg side showed early or high feedforward activation before ground contact during single-leg forward landing.

ObjectivesThis study aimed to clarify the trends of injury occurrence in the Japan national swim team for 15 years and to evaluate the effectiveness of the lumbar injury prevention project. It also aimed to verify the incidence of swimming-related injuries among swimmers by sex, age and swimming style.MethodsThe target group comprised 488 swimmers who participated in the Olympics, Asian Games and Universiade from 2002 to 2016; we compiled data for the total number of injuries in each body part. The lumbar injury prevention project started in 2008 and included two components (deep trunk muscle exercises and evaluation of lumbar disc degeneration using MRI). We analysed the prevalence of lumbar injury before (2002–2008) and after (2009–2016) implementation of the lumbar injury prevention project by χ2 test. We compared age, sex and swim strokes between the injured and non-injured groups by χ2 test and unpaired t-test.ResultsThe most common injury site was the lower back, followed by the shoulder and knee. The lumbar injury prevalence was significantly lower after implementation of the prevention project (23.5% vs 14.8%; pConclusionsLumbar injury prevention intervention might be effective to prevent lower back injury in swimmers. Injury risk factors included female and old age; younger female athletes should prevent the development of injuries as they mature.

[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.

This study aimed to clarify the difference in the onset of EMG activity between eight trunk muscles, including the anterior (QL-a) and posterior (QL-p) layers of the quadratus lumborum during rapid shoulder joint abduction. Thirteen healthy men participated in this study. Electromyography of the QL-a, QL-p, transversus abdominis (TrA), internal oblique (IO), external oblique (EO), rectus abdominis (RA), lumbar multifidus (LMF), lumbar erector spinae (LES) on non-movement side, and middle deltoid (MD) on the movement side were measured. Subjects who were standing in a relaxed position performed rapid shoulder abduction with the dominant hand after light stimulus with or without a 3 kg wrist weight. Two-way ANOVA (muscles × weight conditions) was used to compare the onset of trunk muscles relative to that of MD. There was a significant main effect of the muscles. The onset of the QL-a, QL-p, and TrA was significantly earlier than that of the IO, EO, LMF, and LES (P 0.01). This result suggests that the activities of the QL-a, QL-p, and TrA have a crucial role in controlling the center of mass within the base of support and stabilizing the lumbar spine in the coronal plane during shoulder abduction.

Objective Exercises for lower leg muscles are important to improve function. To examine the influence of foot position on lower leg muscle activity during heel raises. Design Cross-sectional laboratory study. Setting Laboratory. Participants Fourteen healthy men participated in this study. Main outcome measures The muscle activity levels of the tibialis posterior (TP), peroneus longus (PL), flexor digitorum longus (FDL) and medial gastrocnemius (MG) were measured. The heel raises consisted of three foot positions: 1) neutral, 2) 30° abduction, and 3) 30° adduction. The EMG data for five repetitions of each foot position were normalized to maximum voluntary contraction. One-way repeated measure ANOVA was employed for statistical analysis. Results The muscle activity level of TP, PL and FDL was significantly different between the three foot positions during the heel raises. TP and FDL showed the highest activity level in 30° foot adduction while PL demonstrated the highest activity level in 30° foot abduction. Conclusions Heel raises with 30° foot adduction and abduction positions can change lower leg muscle activity; These findings suggest that altering foot posture during the heel raise exercise may benefit patients with impaired TP, PL or FDL function.