Koji Miyashita

Muscular outputs during dynamic bench press under stable versus unstable conditions.

Koshida, S, Urabe, Y, Miyashita, K, Iwai, K, Tanaka, K, and Kagimori, A. Muscular outputs during dynamic bench press under stable versus unstable conditions. J Strength Cond Res 22(5): 1584-1588, 2008-Previous studies have suggested that resistance training exercise under unstable conditions decreases the isometric force output, yet little is known about its influence on muscular outputs during dynamic movement. The objective of this study was to investigate the effect of an unstable condition on power, force, and velocity outputs during the bench press. Twenty male collegiate athletes (mean age, 21.3 ± 1.5 years; mean height, 167.7 ± 7.7 cm; mean weight, 75.9 ± 17.5 kg) participated in this study. Each subject attempted 3 sets of single bench presses with 50% of 1 repetition maximum (1RM) under a stable condition with a flat bench and an unstable condition with a Swiss ball. Acceleration data were obtained with an accelerometer attached to the center of a barbell shaft, and peak outputs of power, force, and velocity were computed. Although significant loss of the peak outputs was found under the unstable condition (p < 0.017), their reduction rates remained relatively low, approximately 6% for force and 10% for power and velocity outputs, compared with previous findings. Such small reduction rates of muscular outputs may not compromise the training effect. Prospective studies are necessary to confirm whether the resistance training under an unstable condition permits the improvement of dynamic performance and trunk stability.

Glenohumeral, Scapular, and Thoracic Angles at Maximum Shoulder External Rotation in Throwing

Background Because a majority of throwing injuries occur near the maximum external rotation (MER) of the throwing shoulder, sports medicine practitioners and researchers have paid special attention to the shoulder kinematics at the MER in throwing. However, little is known about the individual kinematics of the glenohumeral, scapulothoracic, and thoracic joints at the MER. Purpose To demonstrate the glenohumeral, scapulothoracic, and thoracic joint movements and their contribution to the MER in throwing for baseball players. Study Design Descriptive laboratory study. Methods We collected throwing motion data for 20 collegiate baseball players by using 3 high-speed cameras and established 3-dimensional coordinates of each landmark with a direct linear translation method. We then obtained the MER of the shoulder complex, the external rotation angle of the glenohumeral joint, the posterior tipping angle of the scapula, and the thoracic extension angles at the MER in throwing. Results The mean (± standard deviation) value of the MER was 144.2° ± 11.0°. The mean (± standard deviation) values of the glenohumeral external rotation, the scapular posterior tipping, and the thoracic extension angles at the MER were 105.7° ± 15.5°, 23.5° ± 13.9°, and 8.9° ± 7.3°, respectively. Conclusion Our results indicate that not only the glenohumeral joint movement but also the scapular and thoracic movements make major contributions to the MER angle. Clinical Relevance To better understand the pathomechanics of the shoulder complex in throwing, we need to take into account the individual contributions of the glenohumeral, scapulothoracic, and thoracic extension movements to the MER.

Characteristics of trunk lean motion during walking in patients with symptomatic knee osteoarthritis

OBJECTIVE Trunk lean motion on the frontal plane shifts the pressure across the medial-lateral cartilage of the stance limbs knee. The purpose of this study was to investigate trunk lean motion during walking in patients with knee osteoarthritis. MATERIALS AND METHODS The study involved five healthy normal controls and 12 patients with symptoms of knee osteoarthritis (six with unilateral and six with bilateral). The trunk lean angle and the direction during one stride cycle of walking were calculated using a three-dimensional gait analysis. RESULTS There was no significant difference between the three groups (normal, unilateral knee OA, and bilateral knee OA group). However, patients with bilateral limb knee osteoarthritis displayed a tendency to lean their trunk toward the swing side. CONCLUSION This study determined that bilateral OA patients exhibit the characteristic gait which may progress knee OA.

The common mechanisms of anterior cruciate ligament injuries in judo: a retrospective analysis

Background Although high prevalence of anterior cruciate ligament injuries (ACL) in judokas has been reported, there has been very little research concerning events preceding the injury. Objective To determine the common situations and mechanisms of ACL injury in judo. Methods A total of 43 cases of ACL injuries that had occurred during judo competition or practice were investigated, using questionnaires with interviews conducted by a single certified athletic trainer who has 20 years of judo experience to obtain information regarding the situation and mechanism in which the ACL injury occurred. Results The number of ACL injuries when the participants grip style was different from the style of the opponent (ie, kenka-yotsu style) (28 cases) was significantly greater than when the participants grip style was the same as that of the opponent (ie, ai-yotsu style) (15 cases; p<0.001). The number of ACL injuries was significantly higher when the participant was attacked by the opponent than when counterattacked or when attempting the attack (p<0.001). In addition, being attacked with osoto-gari was revealed as the leading cause of ACL injury incidence among the participants (16.8%). Conclusions Grip style may be associated with ACL injury occurrence in judo. In addition, direct contact due to the opponents attack may be a common mechanism for ACL injuries in judo.