| 摘要 |
A swim fin for each foot or a monofin for both feet of a swimmer has an elastic flapping foil that bends away from the ball of the foot on the kicking stroke in which the instep is advanced first, and that is forced against the sole of the of the foot on the opposite stroke. this greatly enhances the efficiency of the kicking action. The free edge of the flapping foil may be curled upward to further enhance the flapping action.
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