Abstract.[Purpose] The purpose of this study was to clarify the intrinsic factors influencing the deep squatting posture and to investigate the utility of ankle joint dorsiflexion measurement using this posture.[Subjects] The study subjects were 71 healthy male individuals. [Methods] The subjects were asked to squatted with their heels down and then were divided into 2 groups: possible squatting and impossible squatting. The anthropometric characteristics of the subjects were assessed, and the flexibility and movement range of the lower extremities were tested. To identify the intrinsic factors influencing the deep squatting posture, a dediscriminant analysis was performed by a stepwise procedure. The sensitivity, specificity, and cutoff values for the factors were evaluated by receiver operating characteristic curve analysis.[Results] Of the 71 participants, 55 were assigned to the possible squatting group and the remaining to the impossible squatting group. Analysis revealed that body weight and ankle dorsiflexion flexibility were significantly associated with ability to assume the deep squatting posture. In particular, ankle dorsiflexion flexibility was strongly associated with the ability to assume this posture. [Conclusion] The impossible squatting group showed reduced ankle dorsiflexion. Thus, the deep squatting posture is useful for easy and objective method for measuring ankle joint dorsiflexion flexibility.

Abstract.[Purpose] The aim of this study was to determine relationship between hip muscle strength and kinematics of the knee joint during single leg squatting and dropping.[Subjects] Twelve healthy subjects participated in this study.[Methods] The knee medial displacement was measured during single leg squatting and dropping using a highspeed camera. Peak isometric muscle strengths of the following muscles were measured hip abductors, hip adductors, hip external rotators, hip internal rotators, knee extensors and knee flexors.[Results] Muscle strength of hip external rotators was associated with knee medial displacement during both single leg squatting (r=-0.69) and dropping (r =-0.59), and muscle strength of knee flexors was associated with knee medial displacement during dropping (r = -0.58).[Conclusion] The present results suggest that hip muscles' strength, particularly hip external rotators' strength are closely associated with knee medial displacement.

ABSTRACT. Background : It is important to acquire fundamental movement skills during childhood. Throwing is a representative manipulative skill required for various intrinsic factors. However, the relationship between intrinsic factors and throwing ability in childhood is unclear. The purpose of this study was to investigate intrinsic factors related to the ball throwing distance of Japanese elementary school children. Methods: Japanese elementary school children from grades 1-6 (aged 6-12 years; n=112) participated in this study. The main outcome was throwing ability, which was measured as the ball throwing distance. We measured five general anthropometric parameters, seven physical fitness parameters, and the Roberton's developmental sequence for all subjects. The relationships between the throwing ability and the 13 parameters were analysed. Results: The Roberton's developmental sequence was the best predictor of ball throwing distance (r=0.80, p!0.01). The best multiple regression model, which included sex, handgrip strength, shuttle run test, and the Roberton's developmental sequence, accounted for 81% of the total variance. Conclusions: The development of correct throwing technique reflects throwing abilities in childhood. In addition to the throwing sequence, enhancement of grip strength and aerobic capacity are also required for children's throwing ability.

Abstract.[Purpose] The aim of this study was to investigate and compare changes in muscle fascicle and tendon tissue behavior during stretching between a weight-bearing position and non-weight-bearing position. [Subjects] The study subjects were fifteen healthy individuals. [Method] Changes in the calf muscle after stretching in a weight-bearing and a non-weight-bearing position were compared using ultrasonography. Weight-bearing and non-weight-bearing stretching were performed for 30 seconds, and the medial gastrocnemius (MG) muscle fascicle length, pennation angle, and Achilles tendon length were measured before and after stretching.[Results] The post-stretching results in both positions showed increased fascicle length, decreased pennation angle, and increased Achilles tendon length compared with the pre-stretching results. Significant interactions were found between weight-bearing and stretching as evidenced by MG fascicle length and Achilles tendon length; specifically, the non-weight-bearing position increased the length more than the weight-bearing position. [Conclusion] This study revealed that while both weight-bearing and non-weight-bearing stretching were able to stretch the MG muscle and the Achilles tendon, non-weightbearing stretching was more effective with regard to extending the MG muscle and Achilles tendon.