The Relationships Between Static Ankle Dorsiflexion Range of Motion and Dynamic Ankle Dorsiflexion, Inversion, and Foot Progression Angles During Sidestep Cutting Maneuver / 体力科学

Although decreased dorsiflexion range of motion (DROM) is linked to ankle inversion sprains and other lower limb injuries, the mechanisms underlying these links are not well understood. The purpose of this study was to examine the relationships between DROM and the ankle dorsiflexion and inversion, and the foot progression angles during a sidestep cutting maneuver. Nineteen healthy subjects participated in this study. The loaded DROM in a flexed- knee position was measured. The foot and ankle motions were assessed during the sidestep cutting maneuver using a 3D motion analysis system. The low DROM group displayed smaller dorsiflexion and inversion angles, and greater external foot rotation, and performed the task using a significantly greater percent of their DROM than the high DROM group during the sidestep cutting maneuver. In addition, the smaller DROM was associated with smaller dorsiflexion angles, greater external foot rotation, and greater maximum dorsiflexion angles as a percentage of DROM during the sidestep cutting maneuver. The decreased DROM may prevent the ankle from becoming stable during the sidestep cutting maneuver, therefore the ankle may be vulnerable position to an inversion sprain. The kinematic patterns displayed by individuals with a decreased DROM may be a compensatory strategy for dorsiflexion deficits, which may be associated with ankle and knee injuries.

ACUTE STATIC STRETCHING REDUCES POWER OUTPUT DURING ISOTONIC MUSCLE ACTION / 体力科学

PURPOSE : The purpose of the present study was to clarify the effect of static stretching on muscular performance with concentric isotonic muscle actions under various loads.METHODS : Concentric isotonic leg extension power outputs were assessed in 12 healthy male subjects after two types of pre-treatment. The pre-treatments included 1) static stretching (SS) treatment performing static stretching of leg extensors, and 2) non-stretching (NS) treatment by resting in a sitting position. Loads during the assessment of the power output were set to 5%, 30% and 60% of the maximum voluntary contractile (MVC) torque with isometric leg extension in each subject.RESULTS : The peak power output following the SS treatment was significantly (P<0.05) lower than that following the NS treatment under each load.CONCLUSION : The present study demonstrated that static stretching significantly reduces power output with concentric isotonic muscle actions under various loads. This result suggests that static stretching decreases power performance.