Medical services at the 2017 Sapporo Asian winter games: injury and illness epidemiology at a 34-nation multisport event.

OBJECTIVES: We describe the medical services provided and report the injuries and illnesses that occurred at the eighth Asian Winter Games 2017. METHODS: A total of 2010 athletes and team officials from 32 National Olympic Committees and 2 guest countries attended this event; medical services were provided for 16 days. Medical data (medical care and physiotherapy) were collected for the same period by the organising committee for athletes and non-athletes (team officials, workforce, media and spectators) and recorded on the electronic medical record system at the medical rooms in the venues and the team residences. RESULTS: We recorded 745 medical encounters (medical care, 443; physiotherapy, 302), of which 549 (74%) were among athletes. There were 214 injuries as well as 144 illnesses and other medical conditions. Of the 1164 athletes, 549 (47%) utilised the services. Ice hockey, snowboarding and alpine skiing had high rate of medical encounters. More than half of the delegations were not accompanied by team doctor, and rate of medical encounters was high in these teams. The vast majority of patients transferred to hospital for further care were mostly athletes (n=36 out of 41), mostly alpine skiers and ice hockey players. CONCLUSION: Injuries and illnesses varied depending on NOC medical staffing and sport events. These data will serve organisers of medical and physiotherapy services in the Asian Winter Games and similar large events.

The kinematics of 1-on-1 rugby tackling: a study using 3-dimensional motion analysis.

BACKGROUND: Although past studies using video analysis indicated that the arm tackle and head-in-front shoulder tackle are possible risks for shoulder dislocation, the underlying mechanisms of tackling-related shoulder dislocation have not been sufficiently investigated. This study aimed to analyze the kinematic aspects of these tackling motions in 1-on-1 tackles in an experimental setting using a 3-dimensional motion-capture system. METHODS: A total of 65 one-on-one tackles were recorded using a marker-based, automatic, digitizing motion-capture system. A documented tackle was classified into 1 of 3 types, which was decided based on the first point of contact on the ball carrier and the head position at the time of impact: shoulder tackle (reference tackle), arm tackle, and head-in-front tackle. The orientations of the head, trunk, and shoulder at impact were calculated and statistically compared with each other. RESULTS: The distribution of tackles recorded in this study was as follows: 38 shoulder, 23 arm, and 4 head-in-front tackles. In comparison with the shoulder tackle as a reference, shoulder abduction on the side of impact was higher in both the arm and head-in-front tackles, while shoulder external rotation was lower in the head-in-front tackles. In the latter type of tackle, significant decreases in neck extension and ipsilateral neck rotation were also indicated. CONCLUSION: The kinematics in both the arm tackle and the head-in-front tackle is significantly different from that in the shoulder tackle and may represent a distinct risk factor for shoulder dislocation.

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.

Oral contraceptive therapy reduces serum relaxin-2 in elite female athletes.

AIM: Recent investigations have demonstrated that athletes with high relaxin-2 levels have a high risk of anterior cruciate ligament injuries, while athletes taking oral contraceptives (OC) have low relaxin-2 levels. It has not yet been clarified whether taking OC reduces relaxin-2 levels. The purpose of this study was to investigate changes in relaxin-2 levels in athletes taking OC. METHODS: Levels of relaxin-2, estradiol, progesterone, luteinizing hormone and follicle-stimulating hormone were measured in serum samples (n = 183) from 106 elite female athletes. Five athletes with serum relaxin-2 concentrations > 6 pg/mL during the luteal phase were recruited to assess the effect of OC therapy. RESULTS: Serum relaxin-2 concentrations were significantly higher during the luteal phase (n = 57) than in the follicular phase (n = 72), or in athletes on OC therapy (n = 10) (P < 0.001, P < 0.001 and P < 0.05, respectively). In the luteal phase, 36.8% (21/57) of the athletes had relaxin levels > 6 pg/mL. In 23 athletes, serum relaxin-2 concentrations were measured during both the follicular and luteal phases, revealing that relaxin-2 levels were significantly higher in the luteal phase compared with the follicular phase. In 5 out of 23 athletes, serum relaxin-2 concentrations were > 6 pg/mL in the luteal phase and during the second cycle of OC therapy, relaxin-2 concentrations decreased dramatically to below the detection limit (0.26 pg/mL). CONCLUSIONS: High serum relaxin-2 concentrations were only detected during the luteal phase. In athletes with high relaxin-2 concentrations during the luteal phase, OC therapy decreased serum relaxin-2 levels.

Shoulder and elbow pain in elementary school baseball players: The results from a nation-wide survey in Japan.

BACKGROUND: Despite recommendations on how to prevent baseball injuries in youths by the Japanese Society of Clinical Sports Medicine, shoulder and elbow pain still frequently occurs in young baseball players. We conducted a questionnaire survey among baseball players at elementary schools across the country to understand the practice conditions of players, examining the risk factors of shoulder and elbow pain in baseball players. METHODS: The questionnaire survey was conducted among elementary school baseball players as members of the Baseball Federation of Japan in September 2015. RESULTS: A total of 8354 players belonging to 412 teams (average age: 8.9) responded to the survey. Among 7894 players who did not have any shoulder and/or elbow pain in September 2014, elbow pain was experienced in 12.3% of them, shoulder pain in 8.0% and shoulder and/or elbow pain in 17.4% during the previous one year. A total of 2835 (39.9% of the total) practiced four days or more per week and 97.6% practiced 3 h or more per day on Saturdays and Sundays. The risk factors associated shoulder and elbow pain included a male sex, older age, pitchers and catchers, and players throwing more than 50 balls per day. CONCLUSIONS: It has been revealed that Japanese elementary school baseball players train too much. Coaches should pay attention to older players, male players, pitchers and catchers in order to prevent shoulder and elbow pain. Furthermore, elementary school baseball players should not be allowed to throw more than 50 balls per day. STUDY DESIGN: Retrospective cohort study.

Application of shear wave elastography for the gastrocnemius medial head to tennis leg.

Muscle strain of the gastrocnemius medial head mainly occurs at the musculotendinous junction (MTJ), and stiffness is a risk factor. Shear wave elastography (SWE) measures elasticity by determining the propagation velocity. The aim of this study was to measure the elasticity of the normal muscle and aponeurosis in the MTJ of the gastrocnemius medial head using SWE, thus obtaining information relevant to muscle strain at this point. Forty-one volunteers (82 legs) were recruited and the gastrocnemius medial heads were examined at four points: three on the aponeurosis, namely at the center of the MTJ (Central), 10 mm proximal to it (Proximal) and 10 mm distal to it (Distal); and at one on the muscle belly (Muscle). The measurements were compared among the points, between males and females, and between younger and middle-aged subjects. Correlations between the elastic modulus and age were also examined. The elastic moduli at Proximal, Central, Distal, and Muscle were 2.82 ± 0.53 m/s, 3.43 ± 0.83 m/s, 4.83 ± 1.56 m/s, and 2.25 ± 0.43 m/s, respectively. These values differed significantly among the points of the aponeurosis, Distal having the highest modulus followed by Central. The elastic moduli were significantly greater in males than females at Distal and Muscle and in younger subjects than middle-aged subjects at Muscle. No significant correlations between elastic modulus and age were observed for any point. SWE could be a feasible method for quantifying the elasticity of muscle and aponeurosis in the MTJ of the gastrocnemius medial head. Clin. Anat. 30:114-119, 2017. © 2016 Wiley Periodicals, Inc.

Epidemiological survey of anterior cruciate ligament injury in Japanese junior high school and high school athletes: cross-sectional study.

We investigated the incidence of anterior cruciate ligament (ACL) injuries among athletes in junior high school and high school by retrospectively reviewing Japan Sports Council notification data registered over a period of 10 years. The total number of ACL injuries during the 10-year period was 30,458, with an incidence of 0.81 per 1000 athlete-years. Among those with ACL injuries, the ratio of girls to boys was 2.8, and incidence of injury was significantly greater among girls than boys (1.36 as against 0.48). Athletes in the 11th grade demonstrated the highest incidence of ACL injuries. We also found that the greatest incidence of ACL injuries was among female high school basketball players; the second highest being among female high school Judo athletes. For sports with a greater number of ACL injuries and a higher injury rate, it is necessary to obtain more detailed data and analysis to determine an effective prevention programme.

Magnetic resonance imaging findings related to sacroiliac joint pain in high-performance athletes.

BACKGROUND: Sacroiliac joint (SIJ) dysfunction in athletes affects competitiveness. However, the pathology and imaging features have not been clarified. OBJECTIVE: To clarify the association between SIJ pain and MRI findings in high-performance athletes. METHODS: Fifty-two Japanese high-performance athletes with or without SIJ pain were recruited. MRI short tau inversion recovery (STIR) semi-coronal and semi-axial images of their SIJs were taken. The relationships between high-signal changes in MRI-STIR and SIJ pain and pain duration were investigated. Six athletes with continuous SIJ pain were prospectively followed. RESULTS: The proportion of athletes with high-signal changes in the SIJ was significantly higher among athletes with SIJ pain for one month or more (76.9%, 10/13) than among athletes with SIJ pain for less than one month (18.2%, 2/11) and among athletes without SIJ pain (28.6%, 8/28). High-signal changes on painful SIJs were most often present in the sacrum. In three of the six athletes who were prospectively followed, the high-signal area and intensity on MRI both diminished as their symptoms improved. CONCLUSIONS: High-signal changes of the SIJ on MRI-STIR images in high-performance athletes may reflect their SIJ pain.

Functional differences in the activity of the hamstring muscles with increasing running speed.

In this study, we examined hamstring muscle activation at different running speeds to help better understand the functional characteristics of each hamstring muscle. Eight healthy male track and field athletes (20.1 +/- 1.1 years) performed treadmill running at 50%, 75%, 85%, and 95% of their maximum velocity. Lower extremity kinematics of the hip and knee joint were calculated. The surface electromyographic activities of the biceps femoris and semitendinosus muscles were also recorded. Increasing the running speed from 85% to 95% significantly increased the activation of the hamstring muscles during the late swing phase, while lower extremity kinematics did not change significantly. During the middle swing phase, the activity of the semitendinosus muscle was significantly greater than that of the biceps femoris muscle at 75%, 85%, and 95% of running speed. Statistically significant differences in peak activation time were observed between the biceps femoris and semitendinosus during 95%max running (P < 0.05 for stance phase, P < 0.01 for late swing phase). Significant differences in the activation patterns between the biceps femoris and semitendinosus muscles were observed as running speed was increased, indicating that complex neuromuscular coordination patterns occurred during the running cycle at near maximum sprinting speeds.

Differences in activation patterns of knee flexor muscles during concentric and eccentric exercises.

The purpose of this study was to clarify the activation patterns among knee flexor muscles during knee flexion exercises by electromyography (EMG) and muscle functional magnetic resonance imaging (mfMRI). Seven male volunteers performed knee flexion exercises with each unilateral limb at 120% of 1 repetition of maximum (1RM) and 50% of 1RM. EMG activity was recorded for the biceps femoris long head, semitendinosus (ST), semimembranosus (SM), and gracilis (G) muscles; mfMRI T2 values in the same muscles were measured at rest and immediately after exercise. The study found that EMG of the ST and G was significantly higher than that of the SM during the exercises at 120% 1RM. T2 value changes in the ST and G were significantly higher than in the biceps femoris long head (BFlh) and SM in both exercises [corrected].It was concluded that the activation patterns among knee flexor muscles during knee flexion were nonuniform for the respective muscles.

Appropriate slice location to assess maximal cross-sectional area of individual rotator cuff muscles in normal adults and athletes.

PURPOSE: We investigated appropriate slice locations for magnetic resonance (MR) imaging evaluation of the maximal cross-sectional area (CSA) of individual rotator cuff (RC) muscles in normal adults and athletes. METHODS: We used a 1.5-tesla MR system with body-array and spine coils to obtain oblique sagittal T(1)-weighted shoulder images of 29 normal adults (16 men, 13 women); 6 national-level competitive swimmers (4 men, 2 women); 10 collegiate-level female badminton players; and 7 collegiate-level male rowers. We calculated the supraspinatus, infraspinatus, teres minor, and subscapularis CSAs at the 0-1 locations on the scapula (dividing scapula width into 11 locations), 0 representing the medial border of the scapula and 1, the glenoid fossa surface. We evaluated the differences in CSAs at relative locations on the scapula for each muscle in normal adults, swimmers, badminton players, and rowers using a one-way analysis of variance followed by the Tukey test (P<0.05). RESULTS: The supraspinatus CSAs were maximal at 0.7 for all groups. The infraspinatus CSAs were maximal at 0.5 for normal men and women and badminton players, 0.4- and 0.5 locations for swimmers, and 0.4 for rowers. The teres minor CSAs were maximal at 0.9 for all groups except the swimmers (1 location). The subscapularis CSAs were maximal at 0.7 in men, swimmers, and badminton players and 0.6 in women and rowers. CONCLUSION: The appropriate slice locations for evaluating maximal CSAs are slightly lateral to the center of the scapula for the supraspinatus and subscapularis, at approximately the center of the scapula for the infraspinatus, and near the glenoid fossa for the teres minor. These slice locations should be clinically useful for morphological and/or function-related assessments of shoulder RC muscles.

A retrospective study of mechanisms of anterior cruciate ligament injuries in high school basketball, handball, judo, soccer, and volleyball.

The purpose of this study was to analyze the mechanism of anterior cruciate ligament (ACL) injuries among male and female high school students across several different sports to understand ACL injury trends.A total of 1000 cases involving high school students who suffered ACL injuries during school activities (soccer, basketball, volleyball, handball, and judo) and who received insurance benefits through the Injury and Accident Mutual Aid Benefit System, were included to clarify the various mechanisms of ACL injuries. The mechanism of ACL injury was divided into contact and non-contact injuries. Contact injuries were further divided into direct and indirect contact injuries. Non-contact ACL injuries were also further divided into landing injuries, which involved jump-landing movements, and cutting and stopping injuries, which involved movement with a change of direction and deceleration.Overall, 99.0% of judo ACL injuries were categorized as contact ACL injuries. With regards to ball sports, the number of non-contact ACL injuries among basketball, volleyball, and handball players was significantly higher than the number of contact injuries (67.0%, 86.5%, and 68.5% respectively). With regards to female soccer and basketball players, the number of indirect ACL injuries was higher than direct injuries (72.2% and 76.7%, respectively).Volleyball was associated with a higher rate of non-contact injuries. Soccer, basketball, and handball were associated with more or similar rates of indirect and non-contact injuries than direct injuries. Judo was associated with a higher rate of contact injuries.

Mortality of Japanese Olympic athletes: 1952-2017 cohort study.

AIM: To evaluate mortality among Japanese Olympic athletes compared with the general population and also evaluate their mortality based on total number of Olympics participation and intensity of sports disciplines. METHODS: Information on biography, vital status, date of birth, date of death and latest follow-up date on Japanese Olympians was retrieved from six online databases and compared. Standardised mortality ratio (SMR) was estimated according to observation periods and years from last participation in the Olympics. To further evaluate the association between mortality and total number of Olympics participation/intensity of sports disciplines within the study population, rate ratios (RRs) adjusted by sex, observation period and attained age group were estimated by a Poisson regression model. RESULTS: A total of 3381 Olympians were included in the analysis. The total person years was 94 076.82. The deaths of 153 (4.53%) Olympians were confirmed, and the overall SMR was 0.29 (95% CI, 0.25 to 0.34). SMRs categorised by years from last participation did not differ significantly. Higher mortality was observed among those who participated in the Olympics twice (RR: 1.52; 95% CI, 1.04 to 2.23) and three times or more (RR: 1.87; 95% CI, 1.08 to 3.25) compared with those who participated just once. Compared with combination of low static and low dynamic intensity category, higher mortality was observed in most combinations of middle-intensity or high-intensity categories. CONCLUSION: Japanese Olympians lived longer than the general population. More frequent participation in the Olympics and higher intensity of sports disciplines were associated with higher mortality.

Kinematics of Rugby Tackling: A Pilot Study With 3-dimensional Motion Analysis.

BACKGROUND: Although improper tackling technique in rugby can affect the outcome of the tackle and lead to head, neck, and shoulder injuries, the effects of the height of the tackle or the side of the leading leg at the time of impact have not been investigated. Hypothesis/Purpose: The purpose was to characterize the trunk orientation at impact during various tackles. It was hypothesized that 3-dimensional motion analysis would be able to capture the critical kinematic differences in the 4 types of tackles studied. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 66 tackles on a tackle bag were recorded among 13 elite rugby players. Four types of tackles were evaluated: the normal shoulder tackle, in which the tackler's dominant shoulder made impact while the leading foot was on the same side as that shoulder; the low tackle, in which the tackler targeted the lower portion of the tackle bag; the opposite-leg tackle, in which the tackler's leading leg was on the opposite side as the shoulder making impact; and the low and opposite-leg tackle, which was a combination of the previous 2 types of tackles. The orientation of the trunk at impact was calculated, and 2-way repeated-measures analyses of variance were used to compare the characteristics of these tackles. RESULTS: Trunk inclination at impact was lower in the low tackle than in the normal tackle ( P < .01), regardless of the side of the leading leg. Trunk bending to the side of the impacted shoulder was lower in the opposite-leg tackle ( P < .01), and these findings were more significant in the normal-height tackles ( P < .01). Trunk rotation to the side of the impacted shoulder was lower in the opposite-leg tackles ( P < .01) and more significant in the lower-height tackles ( P = .03). CONCLUSION: The 3-dimensional motion capture system was effective in investigating the kinematics of rugby tackling. The kinematics in the low and opposite-leg tackles were significantly different from those in the normal shoulder tackle, which may affect tackle performance and the possible risk of contact injury. CLINICAL RELEVANCE: When a rugby coach provides tackling instructions to players, it is advantageous to have information about the kinematics of different types of tackles.

Lumbar intervertebral disk degeneration in elite competitive swimmers: a case control study.

BACKGROUND: The majority of orthopaedic problems experienced by competitive swimmers are related to pain in the shoulder, low back, and knee. Three of 39 national swim team members were hampered in their performance due to lumbar disk herniation at an international competition in 2001. There has been no previous research into lumbar disk degeneration in elite competitive swimmers. HYPOTHESIS: Excessive competitive swimming activities accelerate lumbar disk degeneration. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Fifty-six elite swimmers (high-load group, 35 men and 21 women; mean age, 19.6 years) and a control group of 38 university recreational level swimmers (low-load group, 24 men and 14 women; mean age, 21.1 years) were evaluated for lumbar disk degeneration using magnetic resonance imaging. We compared the prevalence of disk degeneration and the disk level between the 2 groups and further investigated the relationship among their symptoms, swimming styles, and disk degeneration. RESULTS: Thirty-eight (68%) elite swimmers and 11 (29%) controls had degenerated disks at various disk levels, and the prevalence was significantly greater in the elite swimmers (P = .0002). Comparison between the 2 groups of the prevalence of disk degeneration at each level revealed that the disk level of L5-S1 was significantly more frequently degenerated in the high-load group (P = .026). There was no significant relationship observed among the variables of low back pain symptoms, swimming strokes, and disk degeneration. CONCLUSION: Excessive competitive swimming activities might exaggerate lumbar intervertebral disk degeneration, especially in the L5-S1 intervertebral segment.

Hip acetabular dysplasia and joint laxity of female anterior cruciate ligament-injured patients.

BACKGROUND: It has been noted that some female anterior cruciate ligament-injured patients have complaints of both coxalgia and joint laxity. HYPOTHESIS: Female anterior cruciate ligament-injured patients tend to have both acetabular dysplasia and generalized joint laxity. STUDY DESIGN: Cohort study (prevalence); Level of evidence, 2. METHODS: Hip radiographs of 100 female anterior cruciate ligament-injured patients and 40 female athletes without any hip joint complaints or history of anterior cruciate ligament injury were evaluated by measuring their center-edge angle (CEA). In addition, generalized joint laxity tests using 8 items were performed for anterior cruciate ligament-injured patients. Anterior-posterior (A-P) tibiofemoral translation of the uninjured knee was measured using a KT-1000 knee arthrometer to evaluate joint laxity under anesthesia before anterior cruciate ligament reconstruction. RESULTS: The average (± standard deviation) CEA of female anterior cruciate ligament-injured patients was 25.5° ± 5.3° (uninjured side) and 25.8° ± 4.8° (injured side), and that of the control group was 28.2° ± 4.2° (right side) and 29.2° ± 5.7° (left side), both P < .05. Among the 100 patients with anterior cruciate ligament tears, both the generalized joint laxity score and A-P tibiofemoral translation of the group with acetabular dysplasia (CEA of <25°, n = 37) were significantly greater than that of the normal group (CEA of ≥25°, n = 63). There was a negative correlation between the CEA of female anterior cruciate ligament-injured patients and both the generalized joint laxity score and A-P tibiofemoral translation. CONCLUSION: The CEA of female anterior cruciate ligament-injured patients was significantly smaller than that of the control group. Statstical analysis showed a moderate negative correlation between the CEA and generalized joint laxity score. Female athletes with an anterior cruciate ligament injury had an increased prevalence of acetabular dysplasia and generalized joint laxity.

Effects of cooling on human skin and skeletal muscle.

To investigate the effects of cooling on local temperature and circulation in the skin and skeletal muscle at different cooling temperatures. Ten male subjects (mean age 24.9 years) participated in this study. Intramuscular temperatures were measured by inserting two 22-gauge temperature probes (needle length; 8 and 18 mm) into the ankle dorsiflexors, while skin temperature was measured using a thermocouple attached to the leg skin anteriorly. Near-infrared spectroscopy was also used to evaluate the concentration changes in oxygenated, deoxygenated, and total hemoglobin/myoglobin in local skin and skeletal muscle. These measurements were simultaneously performed during the 10-min noncooling, 30-min cooling (cooling pad temperature; 0, 10, or 20 degrees C), and 60-min recovery periods. Under all cooling conditions, skin and intramuscular temperatures decreased during cooling (P < 0.01) and began to increase after the cooling pad was removed. However, these values did not return to baseline values during the recovery period (P < 0.01). Moreover, tissue temperatures tended to show lower values during cooling at lower cooling temperatures. All hemoglobin/myoglobin concentrations also showed a concomitant significant decrease during cooling under three cooling conditions (P < 0.01); the oxygenated and total hemoglobin/myoglobin concentrations did not return to the exact values before cooling during the recovery period. This study suggested that the rate of decrease in tissue temperature depends on the cooling temperature and the effects of cooling on tissue temperatures and circulation tend to be maintained during 60 min post-cooling period despite the cooling temperature.

Non-uniform changes in magnetic resonance measurements of the semitendinosus muscle following intensive eccentric exercise.

This study was designed to determine the regional differences of magnetic resonance (MR) measurements in the hamstrings [biceps femoris muscle long head (BFl) and short head (BFs), semimembranosus muscle (SM), and semitendinosus muscle (ST)] following eccentric knee-flexion exercise. Twelve male volunteers performed eccentric knee-flexion exercise. Maximum isometric torque, plasma creatine kinase (CK) activity, muscle soreness, and MR images of the hamstrings were measured before and immediately following exercise, and on the first, second, third and seventh days following the exercise. Cross-sectional areas (CSAs) and transverse relaxation times (T2s) of the hamstrings were measured from the T2-weightened MR imaging sequences of 30% (proximal), 50% (middle), and 70% (distal) areas of the thigh length. The CSA of the ST at proximal and middle regions had significantly increased on the third day, but no significant changes were found for the BFl or SM. Immediately following exercise, T2 values had increased significantly in the BFs, BFl, and ST. On the third day, T2 values of only ST increased significantly at proximal, middle and distal regions. Significant differences of T2 values between proximal and distal regions in the ST were found for the second, third and seventh days following the exercise. These results suggest that because of the anatomical characteristics of the muscles, the degrees of response following the exercise differed among the muscles and the regions of ST muscle.