| 摘要 |
An enhanced swim fin is provided comprising a flipper blade having an increased effective surface area during movement in a first direction, and a decreased effective surface area during movement in a second direction. The swim fin preferably comprises a staged opening during movement in the first direction, in which the opened flipper blade provides increased flexion as the effective surface area is increased. The swim fin preferably comprises a staged closing during movement in the second direction, in which the opened flipper blade provides decreased flexion as the effective surface area is decreased. In some embodiments of the staged swim fin, a central hinge, generally located longitudinally along the blade on the fin, provides staged opening and flexion. Various embodiments provide fin opening and closing for either forward or backward kicks. The enhanced swim fin is typically attached to a foot, such as for performance, for training, or for physical therapy. Alternate embodiments of the expandable fin blade may be attached to a hand or to an oar or paddle shaft.
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