HYDRODYNAMIC RE-EXAMINATION OF UNDERWATER NON-PROPULSIVE PHASE IN FRONT CRAWL

The purpose of this study was to re-examination of the hand propulsive force (FP) during the entry and catch (EC) phase in a stroke of front crawl. The EC phase was defined as non-propulsive phase (Collet et al., 2000), which is until a hand starts moving backwards after it enters the water and moves forward. The other phases in the stroke was defined as propulsive phase. Twelve male swimmers performed a 20-m front crawl with maximal effort. For estimatinng the FP, six pressure sensors were attched on their right hand and trials were recorded by three-dimentional motion capture system. We calculated %EC that was the ratio of the mean FP in the EC phase to the mean FP in the propulsive phase. As a result, the mean FP in the EC phase was 22.4 ± 12.9 N and the %EC was 29.1%. Therefore, it was considered the EC phase is propulsive phase even though the hand moves forward

CHANGES OF KINEMATICS DURING UNDERWATER UNDULATORY SWIMMING WITH INCREASING SWIMMING VELOCITY

The purpose of this study was to clarify about the changes of the kinematics during underwater undulatory swimming (UUS) with increasing the swimming velocity. Eight male collegiate swimmers performed three UUS trials at the 70%, 80% and 90% velocity of their maximum effort swimming velocity in a water flume. For motion analysis, a motion capture system was used to collect the three-dimensional coordinates. Using the collected coordinates, the kinematic parameters were analyzed in each trial. As the main results, the kick frequnecy increased and the relative duration of the un-propusive phase with hip extension and knee felxion decreased with increasing swimming velocity. Furtheremore, since the peak hip external roation velocity increased with increasing swimming velocity, it was considered that the hip external rotation velocity during the downward kicking related to controll the swimming velocity during underwater undulatory swimming