ABSTRACT
The present study aimed to investigate the profiles of activities of thigh muscles during 100 m sprint running in track and field athletes experienced hamstrings (muscle) strain injury, with specific emphasis on the difference between injured and non-inured legs. The subjects were 20 track and field athletes who were divided into muscle strain injury group (MS) and non muscle strain injury group (NMS). The electromyograms (EMGs) of five thigh muscles (the biceps femoris, semitendinosus, rectus femoris, vastus lateralis and vastus medialis) and knee joint angles were recorded during 100 m sprint running. For NMS, there were no significant differences between the right and left legs. For MS, the averaged EMG of every muscle,expressed as relative to that during maximum voluntary contraction (%mEMG<sub>MVC</sub>), values of the biceps femoris and semitendinosus in the latter phases of takeoff and swing periods were significantly higher in the injured leg than in the non-injured leg. Also, the maximal flexed and extended angles of the knee joint during takeoff and swing period, respectively, for the injured leg were significantly greater than those for non-injured leg. Thus, the present results indicate that track and field athletes experienced hamstrings (muscle) strain injury show by higher EMG activities in the biceps femoiris and semitendinosus of the injured leg at the later phases of swing and takeoff periods during 100 m sprint running. This may be partially related to the running style with a greater extended position of knee joint angles at the corresponding phases.
ABSTRACT
A study was carried out to investigate the application and method of adjusting a cant, and its effect in ski boots. Forty-two professional ski instructors were asked by questionnaire about the application and method of adjusting a cant, and its effect, etc. Simultaneously they were also checked regarding the alignment of the lower extremities. In order to reveal the effect of cant quantitatively, an experiment was performed on a ski-slope. The inclination of the axis of the lower leg was measured at an angulation position on the slope after placing a 1-mm, 3-mm, or 5-mm thick plastic medial wedge between the boot and the ski, so as to give valgus inclination to the heel.<BR>The results and conclusions are summarized as follows ;<BR>1) Twenty-seven of the forty-two subjects used a cant, and about one third of them stated that its effect was unknown.<BR>2) Valgus cant ( (+) cant) had the effect of improving edge-control and decreasing the inclination of the lower leg, whereas varus cant ( (-) cant) had the effect of smoothing the sliding of the ski tail in the latter half of a turn.<BR>3) There was little change in the axial inclination of the lower leg, even when a 5-mm-thick plastic medial wedge was placed between the boot and the ski.<BR>4) A cant compensates not for static malalignment of the lower extremities but for deficiency of joint movement, and should be adjusted according to a skier's individual technical problem, for example poor edge-control, utilizing its merits described in 2) .