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Purpose: To examine differences in resistance exercise-induced hormonal responses among young athletes according to their maturity levels. Materials and Methods: A total of 12 collegiate and 32 junior high school male athletes were enrolled. The junior high school participants were divided into pre–peak height velocity (PHV) and post-PHV groups, according to their PHV ages. The salivary testosterone, cortisol, and human growth hormone levels were analyzed before (pre), immediately after (post), and at 15 minutes after performing body weight resistance exercise. Results: The testosterone levels were higher in the collegiate than in the junior high school group (P P P P P P P Conclusion: Exercise-induced acute hormonal responses to resistance exercise may depend on individuals’ maturity levels, even in those having the same age.

This study aimed to clarify the kinematic, kinetic characteristics associated with lateral ankle sprain.A 16-month prospective cohort study.Laboratory.A total of 179 college athletes.Joint kinematics, moment during single-leg landing tasks, and ankle laxity were measured. The attendance of each participating team, injury mechanism, existence of body contact, presence of orthosis, with or without medical diagnosis, and periods of absence were recorded.Twenty-nine participants incurred lateral ankle sprain during non-contact motion. The Cox regression analysis revealed that greater knee varus peak angle (hazard ratio: 1.16 [95% confidence interval: 1.10-1.22], p 0.001) and greater pelvic internal rotation peak angle toward the support leg were associated with lateral ankle sprain (hazard ratio: 1.08 [95% confidence interval: 1.02-1.15], p = 0.009). The cut-off values for each predictive factor were -0.17° (area under the curve = 0.89, p 0.001) and 6.63° (area under the curve = 0.74, p 0.001), respectively.A greater knee varus peak angle and pelvic internal rotation peak angle after single-leg landing are predictive factors for lateral ankle sprain.

Introduction Maintaining flexibility, often defined as range of motion (ROM), is important. Recently, self-massage using a foam roller (FR) has been used in clinical and/or sports settings to effectively and immediately improve ROM. Many studies have found significant increases in ROM following the FR intervention; however, the mechanism of the effect is unclear. We aimed to clarify this mechanism regarding the ROM effects following the FR intervention by evaluating local tissue and autonomic nervous system responses. Method The study employed a crossover design that included a comparison between non-intervention (CON trial: left leg) and intervention (FR trial: right leg) groups. Fourteen volunteers participated. Nine outcomes (passive maximum ankle ROM [ROM with a specified and non-specified passive strength], tissue hardness, skin temperature, water contents, circumference, blood flow velocity, pressure pain threshold, autonomic nervous system, and heart rate) were investigated before (PRE) and 0 min (POST0), 20 min (POST20), 40 min (POST40), and 60 min (POST60) post intervention. Results Skin temperature, impedance, and circumference changed significantly following the intervention, and increased ROM with non-specified strength was observed. Discussion Although we found that the FR intervention influenced skin temperature, impedance, circumference, and ROM, adaptability to the intervention may differ depending on an individual's characteristics. Females and/or individuals with a high body water content could obtain greater positive ROM effects than males and/or individuals with a low body water content. Conclusion These findings suggest that the FR intervention may be an effective method to improve ROM, with alterations of skin temperature, impedance, and circumference.

The purpose of this study was to examine whether the NHE with an increased lower leg slope angle would enhance hamstring EMG activity in the final phase of the descend. The hamstring EMG activity was measured, the biceps femoris long head (BFlh) and the semitendinosus (ST). Fifteen male volunteers participated in this study. Subjects performed a prone leg curl with maximal voluntary isometric contraction to normalize the hamstring EMG activity. Subsequently, subjects performed the NHE, with the help of a certified strength and conditioning specialist, while the lower leg slope angle were randomly set at 0° (NH), 20° (N20), and 40° (N40). To compare hamstring EMG activity during the NHE variations, the knee flexion angle was set in the range from 0° to 50°, divided into five phases (0–10°, 10–20°, 20–30°, 30–40° and 40–50°), where 0° indicated that the knee was fully extended. To calculate the knee extension angular velocity, the knee flexion angle divided by time, and break point angle (BPA) was the angle at which 10°/s was exceeded. In the statistical analysis, a two-way repeated measures ANOVA was used for the hamstring EMG activity and a one-way repeated measures ANOVA was used for the BPA. The EMG activity of the BFlh and the ST in N20 and N40 was significantly higher than in NH at knee flexion angle of 0–20° (p < 0.05). For the BPA, NH (57.75° ± 13.28°), N20 (36.27° ± 9.89°) and N40 (16.26° ± 9.58°) were significantly higher in that order (p < 0.05). The results of this study revealed that the NHE with an increased lower leg slope angle shifted the BPA to the lower knee flexion angle and enhanced the hamstring EMG activity in the final phase of the descent.

Kenichiro Murata,1 Tsukasa Kumai,2 Norikazu Hirose2 1Graduate School of Sport Sciences, Waseda University, Nishi-tokyo, Japan; 2Faculty of Sport Sciences, Waseda University, Saitama, JapanCorrespondence: Norikazu HiroseFaculty of Sport Sciences, Waseda University, 2-579-15, Mikajima, Tokorozawa, Saitama 359-1192, JapanTel/Fax +81 42-451-1022Email toitsu_hirose@waseda.jpPurpose: Lateral ankle sprain (LAS) in childhood can result in lateral malleolus avulsion fractures; additionally, bone nonunion may occur. Physical maturity relates to the development of bone morphology and physical functionality. It is unknown how changes in physical functionality attributable to physical maturity affect young soccer players with abnormal lateral malleolus (ALM) morphology. Hence, the present study aimed to investigate the bone morphology of the lateral malleolus in young soccer players and to examine its relationship with physical functionality at different maturity levels.Subjects and Methods: Two hundred and ninety young soccer players aged 6– 15 years were included. The presence of ALM was assessed using ultrasonography. The subjects were allocated to three groups based on physical maturity (Pre-, Mid-, and Post-peak height velocity age [PHVA]). The prevalence of ALM and the relationship between ALM and physical maturity were examined for body composition, foot pressure distribution, foot alignment, ankle mobility, and single-leg balance.Results: The prevalence of ALM was 17.6%. For physical maturity, the post-PHVA group showed a decrease in ankle dorsiflexion and eversion and an increase in one-leg hop distance compared to the Pre-PHVA group (P < 0.05). In the ALM group, the center of pressure during heel raising was distributed laterally in the Post-PHVA (P < 0.01), and the weight-bearing dorsiflexion angle was decreased in the Mid- and Post-PHVA (P < 0.05).Conclusion: In the Post-PHVA young soccer players, decreased ankle dorsiflexion and eversion and increased one-leg hop distance were observed. The ALM group exhibited lateral loading during heel raising in the Post-PHVA group and decreased weight-bearing ankle dorsiflexion angle in the Mid- and Post-PHVA groups. The findings indicate the importance of secondary prevention of LAS and ultrasonography. Prospective studies of LAS in young athletes are required in the future.Keywords: lateral ankle sprain, ultrasonography, physical maturity, physical function, soccer

Context: Several studies have reported that self-massage using a foam roller (FR) increased joint range of motion (ROM) immediately. However, the mechanism of increasing ROM by the FR intervention has not been elucidated. Objective: To clarify the mechanism by investigating properties and morphological changes of muscles targeted by the FR intervention. Design: An interventional study. Setting: An athletic training laboratory. Participants: Ten male college volunteers with no injuries in their lower limbs (mean [SD]: age 23.8 [3.2] y, height 173.2 [4.9] cm, weight 69.5 [8.6] kg). Intervention: The FR intervention on the right plantar flexors for 3 minutes. Main Outcome Measures: Maximum ankle ROM, muscle hardness, and fascicle length of the gastrocnemius muscle at the neutral (0°), maximum dorsiflexion, and maximum plantar flexion positions. All measurements were conducted before (PRE) and after (POST) the FR intervention. Results: Dorsiflexion ROM increased significantly at POST (PRE: 13.6° [8.0°], POST: 16.6° [8.4°]; P Conclusions: Dorsiflexion ROM increased significantly by the FR intervention in the present study; however, muscle hardness and fascicle length did not change. FR may affect not only the muscle but also the fascia, tendon, and muscle-tendon unit. The FR protocol of the present study can be applied in clinical situations, because it was found to be effective to increase ROM.

This study investigated the effect of high-intensity cycling re-warm up (RW) within a very short time-frame on the subsequent intermittent sprint performance. Twelve active males completed three trials in random order: control (CON); 3-min RW at 30% of maximal oxygen uptake (VO2max) (RW30); and 1-min RW at 90% of VO2max (RW90). During the experimental trials, participants performed 40-min intermittent cycling exercise followed by 15-min rest. During the rest period, participants completed CON, RW30, or RW90. After the rest period, participants performed the Cycling Intermittent-Sprint Protocol (CISP), which consisted of 10-s rest, 5-s maximal sprint, and 105-s active recovery with the cycles repeated over 10 min. The mean work during sprint for the CISP was significantly higher in both RW trials than in the CON trial (mean±standard deviation; CON: 3539±698 J; RW30: 3724±720 J; RW90: 3739±736 J; p, This study was supported by JSPS KAKENHI Grant Number 17J02878 (to TY) and internal funding from the Waseda University (to MM and NH).

Ankle sprains are the most prevalent injuries, and elevated fear avoidance beliefs after ankle sprain episodes could inhibit athletic performance and contribute to residual symptoms, such as functional and/or mechanical instability. However, it remains unclear how fear avoidance beliefs differ according to conditions of posttraumatic sequelae. The purpose of this study was to determine whether fear of movement/reinjury differed between individuals with and without functional ankle instability (FI, NFI) and healthy controls (CON) and to examine the relationship between fear and ankle joint laxity by sex. Participants (115 male athletes, 105 female athletes) completed the Identification of Functional Ankle Instability, Athlete Fear Avoidance Questionnaire (AFAQ), Tampa Scale for Kinesiophobia (TSK), and ankle joint laxity test. Total 168 athletes (79 males, 89 females) data were eligible for analysis. The results demonstrated that fear of movement/reinjury was lower in individuals in the absence of functional ankle instability although they experienced ankle sprain (FI; TSK=38.6±4.5, AFAQ=27.4±6.2, NFI; TSK=35.7±5.6, AFAQ=24.5±6.6). The fear of movement/reinjury had correlation with ankle joint laxity only in female athletes (TSK; r=0.285, p=0.013, AFAQ; r 0=0.322, p=0.045).

Objective. Joint torque differences between healthy and rehabilitated legs are often measured as a clinical index of recovery from muscle strain injury. Unfortunately, it should be noted that this is a questionable evaluation measure of the muscle after injury because it is a composite value including related cooperating muscles. Meanwhile, the use of ultrasound elastography for the measurement of individual muscle mechanical properties (i.e., muscle hardness) has recently expanded. The purpose of this study was to examine, using ultrasound elastography, the differences in the linear relationship between muscle contraction intensity and muscle hardness during knee extension in athletes who had recovered from grade II rectus femoris muscle strain injury through comparison of the healthy and rehabilitated legs. Methods. Six athletes participated. Rectus femoris muscle hardness, determined during isometric contraction at 10%, 20%, 30%, and 40% of maximum voluntary contraction, was evaluated using ultrasound strain elastography. Results and Conclusion. The results indicated that for the healthy legs, the strain ratios, as indicated by muscle hardness, decreased linearly (became harder) with contraction intensity, but the strain ratios for the rehabilitated legs decreased nonlinearly. These results show the danger of judging the recovery period using only the difference between healthy and rehabilitated muscle strengths and the importance of evaluating individual muscles.

Hamstring strain often occurs when an opponent unanticipatedly perturbs an athlete's movements. We examined the neuromuscular responses of hamstring and trunk muscles during unanticipated trunk perturbations in athletes with and without a history of hamstring strain injury. Male college athletes (11 with a history of a unilateral hamstring injury and 10 without prior injury) knelt while wearing a chest harness attached to a cable that was pulled backward. They were instructed to resist the force isometrically and maintain their position when the perturbations were applied. The pressure was released with or without a cue (CUE or NoCUE). We measured trunk acceleration, three-dimensional kinematic data, and surface electromyography (EMG) signals of the erector spinae, internal oblique, gluteus maximus, biceps femoris long head, and semitendinosus muscles. Maximum trunk acceleration and displacement were greater with NoCUE in both groups (p < 0.05). EMG amplitude did not differ after perturbation of any investigated muscle. The injured group demonstrated a delayed onset of the gluteus maximus and erector spinae muscles in NoCUE versus CUE stimuli (p < 0.05). Athletes with a history of hamstring strain injury exhibited a reduced neuromuscular coordination of the lumbopelvic muscles in response to unanticipated trunk movement.

Limited literature has investigated epidemiology of sports-related fatalities during high school organizes sports in Japan. Therefore, the purposes of this study are to determine the frequency and incidence rate of sports-related fatalities in Japanese high schools by cause and sports, and to examine the type of on-site first responder. Insurance claim data of sports-related fatalities in Japanese high schools reported to Japan Sports Council Injury and Accident Mutual Aid Benefit System between 2009 and 2018 were retrieved as the primary data source. All fatalities were classified into direct or indirect type by the reported etiology and further categorized into cardiac-related, head and neck injury, exertional heat stroke (EHS), or other. Frequency and incidence rate were calculated by cause of death and sports, and incidence rates were expressed per 100,000 athlete-years (AY) with 95% confidence interval (CI). Information regarding first responder to the incident was also retrieved and examined by frequency. A total of 63 sports-related fatalities were analyzed. The overall incidence rate was 0.45 (95%CI = 0.25–0.65) per 100,000AY. The incidence rates of direct and indirect fatalities declined from 0.36 and 0.50 per 100,000AY to 0.28 and 0.00 per 100,000AY, respectively. The leading cause of deaths was cardiac-related (n = 30/63, 47.6%), followed by head and neck injury (n = 15/63, 23.8%) and EHS (n = 14/63, 22.2%). The number of fatalities was highest in male baseball (n = 12/63, 19.0%) and the incidence rate was highest in male judo (4.79 per 100,000 AY, 95%CI: 0.68–8.15). Coach was the most frequently reported first responder onsite (n = 52/63, 82.5%). Medically trained personnel were involved in onsite care in two cases (3.2%). In conclusion, the occurrence of sports-related fatalities has declined over time from 2009 to 2018. To deliver appropriate medical care onsite for better survival, employment of medically trained personnel should be promoted in high school sports setting in Japan.

In this study, we aimed to clarify the characteristics of neuromuscular function, kinetics, and kinematics of the lower extremity during sprinting in track and field athletes with a history of strain injury. Ten male college sprinters with a history of unilateral hamstring injury performed maximum effort sprint on an athletic track. The electromyographic (EMG) activity of the long head of the biceps femoris (BFlh) and gluteus maximus (Gmax) muscles and three-dimensional kinematic data were recorded. Bilateral comparisons were performed for the EMG activities, pelvic anterior tilt angle, hip and knee joint angles and torques, and the musculotendon length of BFlh. The activity of BFlh in the previously injured limb was significantly lower than that in the uninjured limb during the late-swing phase of sprinting (

Background: Throwing injuries of the shoulder and elbow are common among youth baseball players. Hypothesis: A prevention program will reduce the incidence of throwing injuries of the shoulder and elbow by 50% among youth baseball players. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: The authors block randomized 16 youth baseball teams consisting of 237 players aged 9 to 11 years into an intervention group (8 teams, 117 players) and a control group (8 teams, 120 players). The intervention program consisted of 5 stretching, 2 dynamic mobility, and 2 balance training exercises performed during warm-up. Both groups were followed up for 12 months, during which the incidence of shoulder and elbow injuries was recorded. In addition, ball speed during pitching as a performance-related factor and variables of physical function (passive range of motion of the elbow, shoulder and hip, dynamic balance, and thoracic kyphosis angle) were assessed during the pre- and postintervention periods. Results: The incidence of shoulder and elbow injuries in the intervention group (1.7 per 1000 athlete-exposures) was significantly lower than that in the control group (3.1 per 1000 athlete-exposures) (hazard ratio, 1.940; 95% CI, 1.175-3.205; P = .010). The factors related to pitching performance, as assessed by ball speed, tended to increase in the intervention group as compared with the control group ( P = .010). The program also improved shoulder horizontal adduction deficits on the dominant side, hip internal rotation on the nondominant side, and the thoracic kyphosis angle. Conclusion: A prevention program decreases throwing injuries of the shoulder and elbow and enhances the parameter of pitching performance in youth baseball players.

Hirose, N and Tsuruike, M. Differences in the electromyographic activity of the hamstring, gluteus maximus, and erector spinae muscles in a variety of kinetic changes. J Strength Cond Res 32(12): 3366-3372, 2018-This study aimed to clarify the differences in the electromyographic (EMG) activity of the semitendinosus (ST), semimembranosus (SM), biceps femoris long head (BFl), gluteus maximus (GM), and erector spinae (ES) muscles during leg curl and bridge exercises across different knee angles and isometric contraction outputs. Sixteen male volunteers participated in this study. The EMG of all targeted muscles was measured at 20 and 40% of the maximal voluntary isometric contraction (MVIC) in the leg curl and during bilateral and unilateral bridge exercises. The knee flexion angle was randomly set at 30, 60, 90, and 120° during each of the exercises. The obtained data were normalized by the MVIC of the corresponding muscle, and each of the normalized values was compared with that of the ST. The EMG activity of the ST was significantly greater at 120° of knee flexion than that of 30 and 60° of knee flexion during leg curl regardless of intensity (p < 0.05), in contrast with that of the SM and BFl. However, bridge exercises diminished this inverse relationship. The ES activity changed similarly to that of the hamstrings, and no difference was observed in the activity of the GM regardless of different knee angles during bridge exercise(s). The strength and conditioning professionals should alter the knee joint angle and load during bridge and leg curl exercises according to which hamstring muscle they want to strengthen because ST, SM, and BFl EMG activity varies depending on the intensity and knee angles during these exercises.

Background The Kerlan-Jobe Orthopaedic Clinic (KJOC) score has been used to describe various parameters of throwing shoulder and elbow function for the return to play after a long period of rehabilitation, such as after ulnar collateral ligament reconstruction. No study has yet to identify how scapular dyskinesis (SD) in baseball players affects the KJOC score. This study investigated the relationship of the KJOC score to SD evaluated in collegiate baseball players with and without upper extremity injury. Materials and methods The study participants were 30 male collegiate baseball players (13 pitchers) belonging to the National Collegiate Athletic Association D-I conference. Participants were assessed with the KJOC instrument in the beginning (PRE) and end (POST) of the season. The SD test was conducted (PRE) in shoulder flexion to identify SD Results The mean value of KJOC score was significantly less in POST than that of PRE for the pitchers with SD (89.3 and 60.5, respectively; P = .001), whereas no difference was found in the KJOC score between PRE and POST for the pitchers without SD. For the position players, no difference in the mean value of KJOC score was found between PRE and POST, regardless of SD. Conclusion The results of this study provide evidence that collegiate baseball pitchers with mild SD may have lower KJOC scores, particularly setup or relief pitchers.

The semitendinosus (ST) muscle is primarily used during Nordic hamstring exercise (NHE), which is often prescribed for preventing hamstring injury, though the biceps femoris long head (BFlh) muscle that is more susceptible to injuries. Thus, this study aimed to identify the modulation of BFlh muscle activity with different knee flexion angles during NHE using an inclined platform. Fourteen male athletes performed NHE and maintained their position at maximum inclination (NH). Subjects also performed isometric NHE using a platform inclined to 50° (ICL) and 40° (ICH), and the knee flexion angle was controlled to 50° and 30°. The electromyography (EMG) activity of the BFlh, ST, semimembranosus, gluteus maximus, elector spinae, and rectus abdominus muscles was determined during each exercise. The EMG of the ST was higher than that of the BFlh during NHE and the highest of all muscles in all exercises (p < 0.05). Moreover, the activity of the BFlh tended to be higher than that of the ST for ICH than for ICL, regardless of the knee joint angle. The activity of the BFlh becomes equivalent to that of the ST during NHE at a knee flexion angle of less than 50°. These results indicate that performing NHE at a shallow knee flexion angle will enhance the activity of the BFlh muscle.

This study aimed to investigate the influence of the task type on the relative electromyography (EMG) activity of biceps femoris long head (BFlh) to semitendinosus (ST) muscles, and of proximal to distal regions during isometric leg-curl (LC) and hip-extension (HE). Twenty male volunteers performed isometric LC with the knee flexed to 30° (LC30) and 90° (LC90), as well as isometric HE with the knee extended (HE0) and flexed to 90° (HE90), at 40% and 100% maximal voluntary contraction (MVIC). Hip position was neutral in all conditions. EMG activity was recorded from the proximal and distal region of the BFlh and ST muscles. BFlh/ST was calculated from the raw root-mean-square (RMS) amplitudes. The RMS of 40% MVIC was normalized using MVIC data and the proximal/distal (P/D) ratio of normalized EMG (NEMG) was calculated. The BFlh/ST ratio was higher in HE0 than in LC90 during MVIC and 40% MVIC (p

BACKGROUND: Little is known about the activity of the abdominal internal oblique (IO) and lumbar multifidus (LM) muscles relative to kinetic chain exercises performed in a standing position. HYPOTHESIS/PURPOSE: The purpose of this study was to identify the activity of the IO and the LM muscles during weight‐bearing exercises. The authors hypothesized that IO and LM muscle activity would vary with lower body positions during the kinetic chain exercises. METHODS: Nineteen healthy, young, active subjects volunteered to participate. The electromyographic (EMG) activity (via surface EMG) of the abdominal external oblique (EO), IO, and LM muscles on both sides and the rectus femoris and semitendinosus muscles on the dominant side was determined during rhythmical lower body twisting exercise with three lower body positions: straight leg (SL), athletic position (AP), dynamic knee extension (DE) at two exercise speeds: 150 and 90 beats per min. These were reported as % maximum voluntary contraction. Mean EO, IO, and LM muscle activities were also compared with those of common core stability exercises. RESULTS: IO EMG activity was significantly greater in SL than that of AP (p

Although a 3- to 7-min re-warm up (RW) elicits performance and physiological benefits after half-time (HT), a time-efficient and feasible RW protocol is required for the use of an RW in the athletic setting. This study aimed to investigate the effect of a 1-min RW at high-intensity on the performance and physiological responses during the Loughborough Intermittent Shuttle Test (LIST). In a randomized and counterbalanced cross-over design, 12 male amateur intermittent team sports players (soccer, basketball, handball, and lacrosse; age, 22 ± 2 years; height, 1.70 ± 0.08 m; body mass, 65.1 ± 8.3 kg; body mass index, 22.4 ± 1.9 kg m−2; VO2max, 53.5 ± 4.5 ml kg−1 min−1) performed the LIST. The LIST comprised two 45-min halves separated by a 15-min HT. Each half comprised repetitions of exercise cycles consisting of 3 × 20-m walking, 1 × 20-m maximal sprint, 3 × 20-m jogging, and 3 × 20-m running. During the HT, the participants were assigned to a control trial (CON; 15-min seated rest) or an RW trial (1-min running at 90% of the maximal oxygen uptake after a 14-min seated rest). Compared to the CON, the RW prevents reductions in sprint performance at the fourth and sixth periods of the LIST (fourth: 2.4%, p = 0.002, d = 1.68, sixth: 3.6%, p = 0.012, d = 1.74) and a decrement of gastrointestinal temperature during HT (0.5°C, p = 0.010, d = 1.41). Moreover, the RW decreased the electromyogram amplitude of maximal voluntary contraction (MVC) after HT (12%, p = 0.017, d = 1.12) without a decrease of maximal voluntary contraction force, suggesting an increased neuromuscular efficiency (9%, p = 0.048, d = 0.58). The RW also increased the mean heart rate in the initial part of the second half (4 bpm, p = 0.016, d = 0.38). In conclusion, the RW improved sprint performance, core temperature, muscle activation, and heart rate in the second half of the LIST. The findings suggest that the RW should be recommended for intermittent team sports players when longer RWs are not possible.

Proprioceptive function of the lower limbs deteriorates in patients following total hip arthroplasty. Patients show poor balance and rely more on visual information than proprioceptive information. Plantar vibration stimuli can mechanically enhance somatosensory input from the plantar cutaneous mechanoreceptors, thereby improving static balance. Plantar vibration stimuli may improve static balance in patients after total hip arthroplasty. This is the first study to investigate whether plantar vibration stimuli affects static balance during the early phase following total hip arthroplasty.In this cross-over design study, 16 female patients (aged 65.1 ± 11.0 years) received plantar vibration stimuli for 2 minutes or the sham interventions after total hip arthroplasty in a randomized order on different days. The foot centre of pressure was measured for the total path length, mediolateral path length, and anteroposterior path length directions before and immediately after the interventions in the static standing position both with eyes open and closed. Patients were instructed to minimize body sway when standing.A significant increase was observed in the centre of pressure parameters in the eyes closed condition than in the eyes open condition. The centre of pressure parameters for the eyes closed condition was significantly decreased after vibration interventions than that before intervention.This study supports the view that plantar vibration stimuli can change static balance in patients in the early phase after total hip arthroplasty temporarily by up-weighting sensory information. These stimuli may serve as a treatment option for influencing balance following total hip arthroplasty.

Previous studies suggest that marathon running induces lower extremity muscle damage. This study aimed to examine inter- and intramuscular differences in hamstring muscle damage after a marathon using transverse relaxation time (T2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T2 values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T2 changes were observed and that, regardless of muscle, the T2 values of the distal and middle sites increased significantly at D1 and D3 and recovered at D8, although those values of the proximal site remained constant. T2 significantly increased at distal and middle sites of the biceps femoris long head on D1 (p = 0.030 and p = 0.004, respectively) and D3 (p = 0.007 and p = 0.041, respectively), distal biceps femoris short head on D1 (p = 0.036), distal semitendinosus on D1 (p = 0.047) and D3 (p = 0.010), middle semitendinosus on D1 (p = 0.005), and distal and middle sites of the semimembranosus on D1 (p = 0.008 and p = 0.040, respectively) and D3 (p = 0.002 and p = 0.018, respectively). These results suggest that the distal and middle sites of the hamstring muscles are more susceptible to damage induced by running a full marathon. Conditioning that focuses on the distal and middle sites of the hamstring muscles may be more useful in improving recovery strategies after prolonged running.

This study aimed to compare the effect of different density foam rollers on range of motion recovery.Ten active men completed two, 3-day trials in random order. During the experimental trials, all participants performed 2 min of foam rolling (FR) using a medium-density (medium trial) or hard-density (hard trial) foam roller on the right posterior thigh after completing the 90-min Loughborough Intermittent Shuttle Test (LIST). The hip joint range of motion (ROM), muscle hardness, and muscle soreness were assessed before and after the LIST and at 0 min, 20 min, 60 min, 24 h, and 48 h after FR intervention. Serum creatine kinase (CK) concentrations were assessed before the LIST and at 60 min, 24 h, and 48 h after FR intervention. The contralateral leg in each trial was used as a control.The ROM at 0 min, 20 min, 60 min, 24 h, and 48 h after FR intervention were higher in the right leg (the massage leg) than in the left leg (the contralateral leg) (p 0.05). In the right leg, the ROM at 0 min after FR intervention was higher than after the LIST (p 0.05). There were no significant differences between the medium and hard trials for ROM. Muscle hardness, muscle soreness, and serum CK concentration were not affected by FR.FR has a positive effect on ROM recovery. Moreover, the two roller densities provided similar ROM recovery.

Yanaoka, T, Hamada, Y, Kashiwabara, K, Kurata, K, Yamamoto, R, Miyashita, M, and Hirose, N. Very-short-duration, low-intensity half-time re-warm up increases subsequent intermittent sprint performance. J Strength Cond Res 32(11): 3258-3266, 2018-This study investigated the effect of very-short-duration, low-intensity half-time re-warm up (RW) on subsequent intermittent sprint performance. Using a randomized cross-over design, 11 healthy men performed 3 trials. In the experimental trials, participants performed the first 40-minute intermittent exercise followed by a 15-minute half-time. The interventions at half-time were 15 minutes of seated rest (control), 3 minutes of moderate-intensity RW (cycling at 60% of maximal oxygen uptake [V[Combining Dot Above]O2max]; [60% RW]), and 3 minutes of low-intensity RW (cycling at 30% of V[Combining Dot Above]O2max; [30% RW]). After half-time, participants performed the Cycling Intermittent-Sprint Protocol (CISP), which consisted of 10 seconds of rest, 5 seconds of maximal sprint, and 105 seconds of active recovery at 50% of V[Combining Dot Above]O2max, with the cycles repeated over the 20-minute duration. The mean work and electromyogram amplitude during the sprint in the CISP were higher in both RW trials than in the control trial (p < 0.05). Muscle temperature, estimated from the skin temperature, at 60 minutes was higher in the 60% RW trial than in the control and 30% RW trials (p < 0.05). The mean change in oxygenated hemoglobin concentration during active recovery at 55-65 minutes tended to be higher in both RW trials than in the control trial (60% RW trial: p = 0.06, 30% RW trial: p = 0.06). In conclusion, very-short-duration, low-intensity RW increased intermittent sprint performance after the half-time, in comparison with a traditional passive half-time practice, and was as effective as a moderate-intensity RW when matched for total duration.

Background: Concussion causes acute, short-term brain dysfunctions. However, the impact of repetitive concussion history on brain function remains unclear. Objectives: The present study examined the effect of a history of multiple concussions on the cognitive functions and dynamic cerebral blood flow (CBF) regulation in collegiate rugby football players. Methods: Nine male rugby football players with a history of ≤ 1 concussion and nine players with a history of multiple concussions (≥ 4 concussions) participated in this study. Reaction time and working memory were assessed using a neurocognitive assessment device (CogSport; CogState Ltd., Melbourne, Australia). Arterial blood pressure and middle cerebral artery blood velocity (MCAv) were measured continuously throughout the experiment. Dynamic cerebral autoregulation was examined using a thigh-cuff occlusion and release technique. Results: We found a significant difference in the short-term working memory between players with a history of ≤ 1 concussion and those with a history of multiple concussions (P < 0.05). However, dynamic cerebral autoregulation was not significantly different between the two groups. Conclusions: We found a dysfunction in the short-term memory function of collegiate rugby football players with a history of multiple concussions. However, this impairment in brain function was not associated with changes in dynamic CBF regulation.

Background: Programs to prevent anterior cruciate ligament (ACL) injuries in female basketball players are scarce. Also, ACL injury prevention training that focuses on hip joint function has not been reported. Purpose: To determine the effectiveness of a hip-focused ACL injury prevention program in female basketball players. Study Design: Cohort study; Level of evidence, 2. Methods: A prospective intervention study was conducted for 12 years. Incidence rates of ACL injuries were collected in the first 4 years (observation period) from college female basketball players. After the observation period, a hip-focused ACL injury prevention program was implemented for 8 years (intervention period). A total of 309 players (mean ± SD age, 19.6 ± 1.2 years; height, 163.7 ± 5.6 cm; weight, 59.1 ± 5.1 kg; body mass index, 22.0 ± 1.4) were tracked in the observation period and compared with 448 players (age, 19.6 ± 1.1 years; height, 162.6 ± 5.8 cm; weight, 58.0 ± 5.7 kg; body mass index, 21.9 ± 1.5) who participated in the intervention period. Athlete-exposures (AEs), ACL numbers and mechanisms of injury (MOIs), relative risk (RR), absolute risk reduction (ARR), numbers needed to treat (NNT), and compliance were analyzed. Results: There were 16 ACL injuries (13 noncontact MOIs) in the 4-year observation period, whereas 9 ACL injuries (8 noncontact MOIs) were recorded in the 8-year intervention period. The overall ACL injury incidence was 0.25/1000 AEs in the 4-year observation period compared with 0.10/1000 AEs in the 8-year intervention period, respectively. Compared with the 4-year observation period, significant RR reduction was observed (0.38; 95% CI, 0.17-0.87; P = .017) with ARR and NNT of 0.032 (95% CI, 0.027-0.037) and 31.6 (95% CI, 27.1-37.7), respectively, in the 8-year intervention period. The noncontact ACL injury incidence was 0.21 per 1000 AEs during the 4-year observation period compared with 0.08/1000 AEs in the 8-year intervention period, which also showed significant RR reduction (0.37; 95% CI, 0.15-0.92; P = .026), with ARR and NNT of 0.024 (95% CI, 0.020-0.029) and 41.3 (95% CI, 34.6-51.3), respectively. The mean compliance rate during the intervention periods (8 years) was 89%. Conclusion: A hip-focused injury prevention program demonstrated significant reduction in the incidence of ACL injury in female collegiate basketball players.

Background: Youth baseball players are at high risk for elbow injuries, which can lead to future functional disability. Purpose: To evaluate the effectiveness of a prevention program to lower the risk of medial elbow injury in these athletes. Study Design: Cohort study; Level of evidence, 2. Methods: Youth baseball players, 8 to 11 years old, without a history of elbow and shoulder pain, were allocated to either the intervention (n = 136) or control (n = 169) group. The intervention consisted of 9 strengthening and 9 stretching exercises, performed during warm-up or at home, with high compliance defined as completion of the program 1 or more times per week. The following outcome variables were measured: clinical assessment of the elbow and shoulder joint, ultrasonography assessment of the elbow, and assessment of physical function (passive range of motion of the elbow, shoulder, and hip; strength of the shoulder and scapular muscles; and measurement of the thoracic kyphosis angle). The clinical and ultrasonography assessments were measured at baseline and at 3-month intervals over the 1-year follow-up. Physical function outcomes were measured at baseline and at the endpoint of the follow-up. The primary endpoint of effectiveness was the incidence of medial elbow injury. Secondary endpoints were absolute measures of physical function and change in these measures over the 1-year follow-up. Results: The incidence rate of medial elbow injury was significantly lower in the intervention group (0.8/1000 athlete-exposures) than the control group (1.7/1000 athlete-exposures) (hazard ratio, 50.8%; 95% CI, 0.292-0.882; P = .016). The program improved total range of shoulder rotation (dominant side), hip internal rotation (nondominant side), shoulder internal rotation deficit (bilaterally), lower trapezius muscle strength (dominant side), and the thoracic kyphosis angle. Improvements in the following variables of physical function were predictive of a lower rate of medial elbow injury: increased total shoulder total rotation (odds ratio [OR], 0.973; 95% CI, 0.950-0.997), increased hip internal rotation of the nondominant side (OR, 0.962; 95% CI, 0.936-0.989), and decreased thoracic kyphosis angle (OR, 1.058; 95% CI, 1.015-1.103). Conclusion: A prevention program aiming to improve physical function can prevent medial elbow injury in youth baseball players.

Background There is a large amount of information regarding risk factors for fifth metatarsal stress fractures; however, there are few studies involving large numbers of subjects. This study aimed to compare the static foot alignment and distribution of foot pressure of athletes with and without a history of fifth metatarsal stress fractures. Methods The study participants comprised 335 collegiate male soccer players. Twenty-nine with a history of fifth metatarsal stress fractures were in the fracture group and 306 were in the control group (with subgroups as follows: 30 in the fracture foot group and 28 in the non-fracture group). We measured the foot length, arch height, weight-bearing leg–heel alignment, non-weight-bearing leg–heel alignment, forefoot angle relative to the rearfoot, forefoot angle relative to the horizontal axis, and foot pressure. Results The non-weight-bearing leg–heel alignment was significantly smaller and the forefoot angle relative to the rearfoot was significantly greater in the fracture foot group than in the control foot group (P = 0.049 and P = 0.038, respectively). With regard to plantar pressure, there were no significant differences among the groups. Midfield players had significantly higher rates of fifth metatarsal stress fracture in their histories, whereas defenders had significantly lower rates (chi-square = 13.2, P

Background This study examines age-related changes in the quadriceps femoris (QF), subdivided into the vastus medialis oblique (VMO), vastus medialis (VM), rectus femoris (RF), vastus intermedius (VI) and vastus lateralis (VL) in basketball players. Subjects Seventy male basketball players were divided into four groups according to age (12–13, 14–15, 16–17, and 18–20 years). Methods Ultrasonography was used to measure muscle architecture of the VMO, VM, RF, VI and VL. We created cubic approximate expressions and calculated inflexion points to evaluate peak growth age of each muscle head. Results Significant interactions were observed for all QF parts (p < 0.01–0.001). Muscle thickness (MT) in all QF parts was significantly lower in 12–13-year olds than in 18–20-year olds (p < 0.01–0.001). Significant differences were recognised between 12–13 and 16–17-year olds in VM (p < 0.001), RF (p < 0.001) and VL (p = 0.007). MT was significantly lower in 14–15-year olds than in 16–17-year olds in the VM (p = 0.007) and RF (p = 0.026) and in 18–20 year olds in the VM (p < 0.001), RF (p = 0.036) and VI (p < 0.001). Peak growth age was estimated for each QF part (VMO, 155.0 months; VM, 187.8 months; RF, 212.2 months, VI, 188.9 months; VL, 181.1 months). Conclusion QF parts have different growth rates due to differing functions in each muscle head.

Shinshiro Mineta,1 Takayuki Inami,2 Raldy Mariano,3 Norikazu Hirose4 1Graduate School of Sport Sciences, 2Institute of Physical Education, Keio University, Hiyoshi, Yokohama, 3Graduate School of Asia-Pacific Studies, Waseda University, Shinjuku, Tokyo, 4Faculty of Sport Sciences, Waseda University, Higashifushimi, Nishitokyo, Japan Introduction: Center of pressure (COP) is a sudden displacement at the time of a lateral ankle sprain (LAS). It has been suggested that the distribution of plantar pressure and the quantity of COP displacement are important for assessing the risk of LAS. Therefore, we evaluated the plantar pressure during a single-leg balance test with eyes closed (SLB-C) to identify the factors and characteristics of plantar pressure in people with repeated cases of LAS.Methods: We recruited 22 collegiate athletes and divided them into an instability group (IG; n=11) and a control group (CG; n=11). We measured the distribution of plantar pressure and lower extremity muscle activity during a SLB-C along with static alignment and isometric ankle strength.Results: The fibularis longus (FL) activity was significantly lower in the IG than in the CG. The lateral plantar pressure (LPP)/medial plantar pressure (MPP) ratio was also higher in the IG than in the CG. In addition, the LPP/MPP ratio was correlated with the tibialis anterior (TA)/FL ratio.Conclusion: These results suggest that increased lateral plantar pressure is related to decreased FL activity and increased TA/FL ratio. Keywords: chronic ankle instability, ankle sprain, postural stability, soccer, prevention

The purpose of this study was to identify the period of the gait cycle during which the hamstring muscles were likely injured by estimating the magnitude of tensile force in each muscle during overground sprinting. We conducted three-dimensional motion analysis of 12 male athletes performing overground sprinting at their maximal speed and calculated the hamstring muscle-tendon length and joint angles of the right limb throughout a gait cycle during which the ground reaction force was measured. Electromyographic activity during sprinting was recorded for the biceps femoris long head, semitendinosus, and semimembranosus muscles of ipsilateral limb. We estimated the magnitude of tensile force in each muscle by using the length change occurred in the musculotendon and normalized electromyographic activity value. The study found a quick increase of estimated tensile force in the biceps femoris long head during the early stance phase of the gait cycle during which the increased hip flexion angle and ground reaction force occurred at the same time. This study provides quantitative data of tensile force in the hamstring muscles suggesting that the biceps femoris long head muscle is susceptible to a strain injury during the early stance phase of the sprinting gait cycle.

The purpose of this study was to investigate growth changes in human plantar flexor muscle and tendons. In addition, we ascertained whether growth changes in muscle and tendon were more closely related to skeletal age than chronological age. 22 elementary school children (ESC), 19 junior high school students (JHS), and 23 young adults (ADT) men participated in this study. Maximal strain and hysteresis of tendon structures and cross-sectional area of Achilles tendon were measured using ultrasonography. In addition, skeletal age was assessed using Tanner-Whitehouse III method. Maximal strain of ESC was significantly greater than that of other groups, while no significant difference was observed between JHS and ADT. There was no difference in hysteresis among 3 groups. Relative cross-sectional area (to body mass(2/3)) of ADT was significantly smaller than that of other groups. For ESC and JHS, measured variables of muscle and tendon were significantly correlated to both chronological and skeletal ages. These results suggested that immature musculoskeletal system was protected by more extensible and larger tendon structures in ESC and only by larger tendon structures in JHS, respectively. Furthermore, there were no differences in correlation coefficient values between measured variables of muscle and tendon and chronological or skeletal ages.

Background: The risk of anterior cruciate ligament (ACL) injury is higher in female soccer players than in male soccer players. The most common reason for non-contact ACL injury has been found to be a cutting or stopping maneuver combined with deceleration and landing from a jump. In a previous study, there was no difference in the incidence of ACL injury between offensive and defensive players and in the risk of ACL injury between goalkeepers and other players. Recently studies reported that the most frequent injury situation was pressing in male players. However, the most common type of situation associated with ACL injury in female soccer players has not been clarified. Objectives: The purpose of the present study was to identify the most common type of situation associated with ACL injury in female soccer players. Methods: We handed out questionnaires to 80 female soccer players with a history of ACL injury (90 ACL injuries). The players were asked about the injury characteristics, injury circumstance, maneuver being performed when the injury occurred, and playing type associated with the injury. The players responded to the questionnaire under the guidance of the medical staff of each team. Results: The 80 female soccer players reported a total of 90 ACL injuries during soccer. Among 55 non-contact injuries, 29 (55%) occurred during a cutting maneuver and 22 (44%) occurred during pressing. On assessing the frequency distributions of playing type (pressing vs. others) and body contact (contact vs. no contact), we found that non-contact injuries at pressing were significantly more common than contact injuries at pressing (odds ratio: 3.03; 95% confidence interval, 1.11 - 8.25, P = 0.036) Conclusions: ACL injury often occurs as non-contact injury during pressing at the time of defense, regardless of the playing area, in female soccer players.

The aim of this study was to examine the in‰uence of milk peptide intake on the recovery from muscle damage following high-intensity eccentric exercise. To clarify this issue, we designed a cross over comparison study between peptide intake and control after eccentric calf raise exercise. Six healthy male volunteers (ranging from 19 to 22 years) performed high-intensity eccentric calf raise exercise. The CK, MRI T2 value of the calf were measured at pre-, post-, and on, day 1, 2, 3, 5 and 8 following the exercise to evaluate muscle damage as well as muscle soreness using a visual analog scale (VAS). Statistical diSerences in all measurements between the peptide and control condition were analyzed using two-factorial ANOVA. The peak value of each meas

The aim of the present study was to clarify relationships among the distribution of birth month, maturation and body size in young soccer players. We therefore examined physical and maturational differences between selected players, who were considered to have higher potential to play soccer at a professional level as decided subjectively by coaches, and unselected players. Participants were 332 elite soccer players (mean age = 12.2 +/- 1.5 years; range = 9.1-15.0 years). Participants were divided into six categories (under = U10 to U15), depending on chronological age. Height, body mass skeletal age and maturation difference (skeletal age - chronological age) were compared among four groups (quarter = Q1 to Q4) depending on month of birth. Overall, the distribution of players across the four quarters was skewed such that numbers were greatest in Q1 and smallest in Q4. No significant differences in maturation difference were observed between birth quarters in any age category. On the other hand, except for the U14 age category, there were no significant differences in height between Q4 and Q1 players. However, the height of Q4 players was significantly smaller than those of Q1 in three (U11, U13 and U14, P0.01) of six categories when maturation difference was statistically controlled. Our results suggest a clear bias toward quarter of birth and this bias may depend to some extent on differences in individual skeletal age and body size. Individual biological maturation should thus be considered when selecting adolescent soccer players.

In this study, we examined the relationship between birth-month distribution, skeletal age, height, and weight in adolescent soccer players. The participants were 271 well-trained male adolescent soccer players aged between 9.1 to 15.9 years (N=101 for U12, N=132 for U15, and N=38 for U18). They were divided into four groups according to their month of birth (Q1: Apr-Jun, Q2: Jul-Sep, Q3: Oct-Dec, and Q4: Jan-Mar). Then, the number of players in each group was compared with the standard population of children in Tokyo. Our result showed significant asymmetries in the birth-month distribution for participants of all age groups (p

This study aimed to investigate the in vivo kinematics of shear modulus of the lower leg muscles in patients with medial tibial stress syndrome (MTSS). The study population included 46 limbs with MTSS and 40 healthy limbs. The shear modulus of the medial head of the gastrocnemius, lateral head of the gastrocnemius, soleus, peroneus longus and tibialis anterior muscles were measured using shear wave ultrasound elastography. As a result, the shear modulus of the lower leg muscles was significantly greater in patients with MTSS than in healthy patients (p < 0.01). Based on the differences in shear modulus of lower leg muscles between the patients with MTSS and healthy patients, the measurements obtained via shear wave ultrasound elastography could be used to evaluate risk factors of MTSS.

Development in the coastal zone was focused on from functional aspects such as utilization and protection. In recent years, responding to the social demand for nature conservation, numerous projects have been carried out, seeking ways of coexistence with nature. This report presents an outline of the planning, design, construction and monitoring of such an experiment on how breakwaters can be harmonized with nature. Three types of breakwaters were constructed at Maruyama Fishing Port in Hyogo prefecture to compensate for the loss of seaweed beds due to reclamation. In a survey carried out for three years after construction, the situation was judged to have reached mid succession as the number of species and the diversity index of the seaweeds and phytal animals had increased.

PURPOSE In our previous study, we found that injection of lidocaine into intact knees reduced the maximal voluntary contraction (MVC) and integrated electromyogram (I-EMG) of the quadriceps femoris (QF). This study was designed to investigate changes in the MVC and I-EMG of the QF in response to lidocaine, in patients with anterior cruciate ligament (ACL) lesion, to evaluate alpha-motoneuron activity innervating the QF. METHODS The MVC of knee extension and I-EMG of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles were measured in eight patients with ruptured ACL, before and after lidocaine injection into the knee. RESULTS There were no significant differences between preinjection and postinjection values of MVC (preinjection: 167 +/- 49 N.m; postinjection: 164 +/- 55 N.m) and I-EMG (preinjection: VL: 0.11 +/- 0.06, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.04) (postinjection: VL: 0.12 +/- 0.07, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.05). CONCLUSION Our results indicated that hindrance of afferent feedback from the knee in patients with ACL rupture did not significantly change alpha-motoneuron activity. Lidocaine injection into the knee joint of the subjects in this study only attenuated afferent feedback from mechanoreceptors in the knee joint cavity, but not in the ACL, as afferent feedback from ACL was already lost due to ACL rupture. This indicated that attenuation of afferent feedback from mechanoreceptors in the knee joint cavity other than the ACL did not significantly decrease the activity of alpha-motoneurons innervating the QF during MVC exertion. Therefore, our findings provide evidence that afferent feedback from the ACL has a major influence on the MVC exertion of the QF.

Background No firm consensus has been established regarding the risk factors for stress fracture of the 5th metatarsal because of a lack of large-scale prospective studies. Objective The purpose of this study was to clarify the risk factors for a stress fracture of the 5th metatarsal. Design Cohort study. Setting Prospective study with well-trained varsity players. Participants One hundred and sixty healthy collegiate male football (soccer) players. Assessment of Risk Factors The medial lateral arch ratio of the foot, leg-heel alignment with weight-bearing (WLHA), LHA without weight-bearing (NLHA), relative angle of the forefoot to the hindfoot (FA-H), and plantar pressure during the heel raise position were measured. Rearfoot and forefoot alignment were evaluated from images using Image J. The plantar pressure distribution was measured using a plate-type lower limb GP-6000 weighted meter and pressure distribution-measuring MD-1000 device from Anima Co., Ltd. Main Outcome Measurements The measurements from players who were diagnosed with a stress fracture of the 5th metatarsal were compared with the measurements from non-injured players. Results Four players were diagnosed with a stress fracture of the 5th metatarsal. The arch ratio, WLHA, and FA-R of the injured players were higher than those of the non-injured players (17.8±0.21 vs. 1.68±0.26, −3.79±2.5° vs. −4.24±2.93°, 4.34±3.62° vs. 3.19±5.18°). The NLHA of the injured players was lower than that of the non-injured players (3.08±2.29° vs. 6.03±4.51°). The plantar pressure of the injured players tended to be located in a more lateral position compared with the non-injured players during heel raise (55.41±1.59% vs. 47.93±4.59%). Conclusions Stress on the lateral side of the foot during heel raise may cause stress fractures of the 5th metatarsal.

Background Previous meta-analyses have revealed that effective programs to prevent anterior cruciate ligament (ACL) injuries in female basketball players have not been established. Objective To investigate the effects of an ACL injury prevention program focused on improving hip joint function in female basketball players. Design Cohort study. Setting Intervention study for well-trained varsity athletes. Patients (or Participants) Four hundred eighty-nine (180 intervention and 309 control) female varsity division II basketball players (18–22 years of age) participated in this study. Interventions (or Assessment of Risk Factors) The prevention program consisted of education (injury mechanism, neutral position, etc.) and neuromuscular training to improve hip joint function (jump-landing exercise with a band, hip external rotator and abductor strength training, and balance exercises). Players were guided through this program by several physical therapists. They were instructed to keep the knee and toe in a neutral position in the jump-landing exercise. The intervention group performed this program three times a week throughout the season. The control group maintained their routine warm-up session. All ACL injuries were verified by arthroscopy or magnetic resonance imaging findings. Main Outcome Measurements The 1000 athlete-exposure (1000 AE) and relative risk index (intervention vs. control) of ACL injuries were calculated and compared between the groups using the χ2 test. Statistical significance was set at P Results Three ACL injuries occurred in the intervention group, whereas 16 occurred in the control group. The incidence of injury in the intervention and control groups was 0.08/1000 AE and 0.25/1000 AE, respectively. The relative risk index was 0.32 (95% CI, 0.092–1.086; P=0.053, χ2 test). Conclusions Prevention programs to reduce ACL injuries may be beneficial in well-trained female basketball players.

Background There is little information about the effect of hamstrings training on hip and knee joint function, morphology of each hamstring muscle, and the rate of injury incidence. Objective To clarify the effect of hamstrings training on H:Q strength ratio in hip and knee joint, the morphological adaptations of each hamstring muscle, and the rate of strain injury incidence. Design Prospective, randomized controlled trial. Setting Collegiate, elite division. Participants 23 healthy collegiate Lacrosse players were recruited voluntarily, and 20 (39 limbs) of them finished the study. Interventions Subjects were randomly divided into 3 groups; Single-leg Deadlift (DL) intervention, Nordic Hamstrings (NH) intervention, and control (CR). DL and NH groups joined the training program in twice a week for 6 months. Main Outcome Measurements Before (Pre) and 1, 3, and 6 months after training period, isokinetic strength testing was conducted to measure flexion and extension torques in hip and knee joint, and magnetic resonance imaging to determine the cross sectional area (CSA) of each hamstring muscle. Results After the training of 3 months, only in DL group, significant increase of hip extension torque (+25.2±9.4%) and H:Q ratios in the hip joint (1.28±0.43→1.61±0.48) were found, and significant increase of CSAs were found in biceps femoris long head (+12.0±3.7%) and semimembranosus (+25.5±4.1%) muscle (P Conclusions Hip extension (Single-leg Deadlift) exercise training may be useful for preventing and rehabilitating from hamstring strain injury by stimulating hypertrophy in biceps femoris long head and semimembranosus muscle and promoting improvements in hip extensor strength and H:Q ratio in hip joint. These data may provide compelling evidence to warrant the further exploration of hip extension oriented exercises in hamstring strain injury prevention protocols.

The purpose of this study was to compare the morphological and mechanical properties of the human patellar tendon among elementary school children (prepubertal), junior high school students (pubertal), and adults. Twenty-one elementary school children, 18 junior high school students, and 22 adults participated in this study. The maximal strain, stiffness, Young’s modulus, hysteresis, and cross-sectional area of the patellar tendon were measured using ultrasonography. No significant difference was observed in the relative length (to thigh length) or cross-sectional area (to body mass2/3) of the patellar tendon among the three groups. Stiffness and Young’s modulus were significantly lower in elementary school children than in the other groups, while no significant differences were observed between junior high school students and adults. No significant differences were observed in maximal strain or hysteresis among the three groups. These results suggest that the material property (Young’s modulus) of the patellar tendons of elementary school children was lower than that of the other groups, whereas that of junior high school students was already similar to that of adults. In addition, no significant differences were observed in the extensibility (maximal strain) or viscosity (hysteresis) of the patellar tendon among the three groups.

Background The purpose of this study was to compare the elastic properties and size of tendinous structures and muscle architecture for knee extensors and plantar flexors in boys and men. Methods Twenty-two early pubescent boys (9.6–12.7 yrs) and 23 young adult men (19.8–26.2 yrs) participated in this study. The maximal strain and thickness of tendinous structures for knee extensors and plantar flexors were measured using ultrasonography. In addition, the fascicle lengths of vastus lateralis and medial gastrocnemius muscles were measured. Findings The maximal strain of tendinous structures for plantar flexors was significantly greater in boys than in men, while there was no difference in the maximal strain for knee extensors between the two groups. The relative thickness (to body mass 1/3 ) of Achilles tendon was significantly greater in boys than in men, although there was no difference in that of patellar tendon between the two groups. The relative fascicle length (to limb length) of vastus lateralis muscle was significantly lower in boys than in men, although there was no difference in that of medial gastrocnemius muscle between the two groups. Interpretation These results suggest that the amount of changes in the elastic properties and sizes of tendinous structures and in the fascicle lengths from early pubescence to maturity is different for different muscle groups (in particular, the knee extensors and the plantar flexors).

The purpose of this study was to obtain evidence to support the hypothesis that motor unit recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture. We compared muscle torque per unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold motor unit recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI. Tests revealed that the mean muscle torque per unit volume of the uninjured and injured sides was significantly lower than those of the control group. This study demonstrated that the values of the muscle torque per unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of motor unit recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

Background: Anterior cruciate ligament (ACL) injury is one of the most devastating injuries in sports. Althoughmany studies have demonstrated successful prevention program in research settings, the rate of ACL injury remains high. One of the reasons might be a low participants adherence to injury prevention training programs. More effective and efficient strategy is needed to reduce the rate of ACL injury. This study implemented a simplified skill training program that was specific to basketball in order to encourage the athletes and coaches to perform the program with a high adherence. This study also attempted to train younger athletes than those who were usually targeted, as learning proper movement skills could be better achieved in younger population. Purpose:To evaluate the effects of skill training on lowerextremity kinematics and muscle function in female pubertal athletes. Methods: Nine female basketball players (age 12.6± 0.5 years) participated in the study. A 12-week skill training program was implemented. The focus of the program was to ensure proper landing techniques. The skills required in basketball, such as jumping, stopping, and pivoting, were practiced with the instruction to use proper body mechanics. Isokinetic strength of the hip and knee joints, and lower-extremity kinematics and preparatory muscle activities during drop vertical jumps were evaluated before and after the training period. The data were compared between the preand post-test by using a paired t-test or a Wilcoxon signed-rank test. Results: The knee abduction angle at 40ms after ground contact, when ACL injuries typically occur, was significantly decreased after the training period (−1.9± 5.8 vs. −4.5± 3.8◦, p= 0.04). The preparatory muscle activities of the rectus femoris, vastus medialis, and gluteus maximus were significantly decreased (rectus femoris: 38.0± 25.2 vs. 21.5± 7.7%MVIC, p= 0.04; vastusmedialis: 37.6± 22.8 vs. 23.0± 13.1%MVIC, p= 0.01; gluteus maximus: 13.8± 9.2 vs. 5.4± 1.8%MVIC, p= 0.02) and the isokinetic strength of knee flexion was significantly increased after the training period (0.83± 0.18 vs. 0.94± 0.10Nm/kg, p= 0.04). These changes in the muscle function might suggest an improved proficiency in the performance of the landing task. Conclusion(s): A 12-week training program that focused on proper landing skills might be effective in reducing the knee abduction angle at 40ms after ground contact. The training program also changed the preparatory muscle activity and isokinetic strength. These results suggested that the skill training program might have improved not only the landing skills but also the neuromuscular function in female pubertal athletes. Implications: Simplified skill training might be sufficient for young athletes to modify the landing technique and muscle function. The implementation of the skill training should be encouraged in pubertal girls to reduce the risk of developing ACL injury.

No studies have identified the direct effect of changes in cerebral blood flow (CBF) on cognitive function at rest and during exercise. In this study, we manipulated CBF using hypercapnic gas to examine whether an increase in CBF improves cognitive function during prolonged exercise. The speed and the accuracy of cognitive function were assessed using the Stroop color‐word test. After the Stroop test at rest, the subjects began exercising on a cycling ergometer in which the workload was increased by 0.5 kilopond every minute until a target heart rate of 140 beats/min was achieved. Then, the subjects continued to cycle at a constant rate for 50 min. At four time points during the exercise (0, 10, 20, 50 min), the subjects performed a Stroop test with and without hypercapnic respiratory gas (2.0% CO2), with a random order of the exposures in the two tests. Despite a decrease in the mean blood flow velocity in the middle cerebral artery (MCA Vmean), the reaction time for the Stroop test gradually decreased during the prolonged exercise without any loss of performance accuracy. In addition, the hypercapnia‐induced increase in MCA Vmean produced neither changes in the reaction time nor error in the Stroop test during exercise. These findings suggest that the changes in CBF are unlikely to affect cognitive function during prolonged exercise. Thus, we conclude that improved cognitive function may be due to cerebral neural activation associated with exercise rather than global cerebral circulatory condition., e12163 We found that even prolonged exercise improved cognitive function, which was unlikely to have been affected by changes in cerebral blood flow. Exercise‐induced improvements in cognitive function may be due to cerebral neural activation associated with exercise rather than cerebral circulatory condition. The finding would advance our understanding of physiological mechanisms underlying the regulation of the cognitive function.

Background The rearfoot motion during sports activities in patients with the medial tibial stress syndrome (MTSS) is unknown. This study aimed to investigate the difference in kinematics of the rearfoot in MTSS patients (eight male soccer players) and control participants (eight male soccer players) during a forward step. Methods Sixteen male soccer players, including eight players with MTSS, participated. Forward step trials were recorded with cineradiographic images obtained at a sampling rate of 60 Hz. Geometric bone models of the tibia and talus/calcaneus were created from computed tomography scans of the distal part of one lower limb. Following a combination of approaches, anatomical coordinate systems were embedded in each bone model. The talocrural joint motion (relative motion of the talus with respect to the tibia) and subtalar joint motion (relative motion of the calcaneus with respect to the talus) were examined. Results A significantly larger range of internal/external rotation and inversion/eversion motion was observed in the subtalar joint of MTSS patients compared to healthy controls (P