BACK-PLATE STARTING PLATFORM HAS ADVANTAGES OVER THE CONVENTIONAL PLATFORM

Nomura, T., Takeda, T., & Takagi, H. (2010). Influences of the back plate on competitive swimming starting motion in particular projection skill. A paper presented at the XIth International Symposium for Biomechanics and Medicine in Swimming, Oslo, June 1619, 2010.

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This study identified the influences of the back plate on the swimming starting motion and in particular, the projection skill. Male college swimmers (N = 10) performed the track start from the conventional platform and the platform with a back plate. A video camera was used to record the performance of each trial from the side view. The projection motion was divided into the set position, acceleration phase, take-off, and flight phase. Fifteen variables were analyzed

At the set position, the back-plate position of the center of mass was significantly more forward than the conventional position. The back-plate rear-leg knee angle was significantly smaller than on the conventional platform. The back-plate projection angle while still in contact with the platform was significantly more horizontal than the conventional projection angle. At take-off, the projection angles of the centers of mass were ~-8.2 for the back-plate and ~ -10.5 for the conventional platform. The vertical velocity components of the center of mass at the take-off were ~ -0.65 m/s for the back-plate platform and ~ -0.81 m/s for the conventional platform. Other items for the take-off and for flight were not significantly different.

At the set position, the center of mass of the back-plate position displaced forward. That is in agreement with a study of the squatting-to-standing movement where heel elevation primarily influenced postural adjustment as anterior displacement of the hip. In the back-plate position, the rear knee angle was about 90. The isometric force-angle relationship of knee extension produces largest forces were between 105-120. Therefore, the rear knee of the back-plate position should possibly be more extended.

Implication. The back-plate starting position produces a more horizontal flight angle and initially positions the swimmer slightly more forward than that exhibited with the conventional flat-angled starting platform.

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