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amputee swing leg speed

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  • amputee swing leg speed

    Li Li raises an interesting point and he proposes a way to test it.

    But, a study by Peter Weyand et al. suggests that
    minimizing contact time and not swing time is the
    key variable to consider.
    I really like Peter's study, not everybody feels
    that his inferences are correct.
    abstract and free pdf link pasted below.

    Rodger Kram

    J Appl Physiol 89: 1991-1999, 2000;

    Faster top running speeds are achieved with
    greater ground forces not more rapid leg movements
    Peter G. Weyand, Deborah B. Sternlight, Matthew J. Bellizzi, and Seth Wright

    Concord Field Station, Museum of Comparative
    Zoology, Harvard University, Bedford,
    Massachusetts 01730

    We twice tested the hypothesis that top running
    speeds are determined by the amount of force
    applied to the ground rather than how rapidly
    limbs are repositioned in the air. First, we
    compared the mechanics of 33 subjects of
    different sprinting abilities running at their
    top speeds on a level treadmill. Second, we
    compared the mechanics of declined (6°) and
    inclined (+9°) top-speed treadmill running in
    five subjects. For both tests, we used a
    treadmill-mounted force plate to measure the time
    between stance periods of the same foot (swing
    time, tsw) and the force applied to the running
    surface at top speed. To obtain the force
    relevant for speed, the force applied normal to
    the ground was divided by the weight of the body
    (Wb) and averaged over the period of foot-ground
    contact (Favge/Wb). The top speeds of the
    33 subjects who completed the level treadmill
    protocol spanned a 1.8-fold range from 6.2 to
    11.1 m/s. Among these subjects, the regression of
    Favge/Wb on top speed indicated that this force
    was 1.26 times greater for a runner with a top
    speed of 11.1 vs. 6.2 m/s. In contrast, the time
    taken to swing the limb into position for the
    next step (tsw) did not vary (P = 0.18). Declined
    and inclined top speeds differed by 1.4-fold
    (9.96 ± 0.3 vs. 7.10 ± 0.3 m/s, respectively),
    with the faster declined top speeds being
    achieved with mass-specific support forces that
    were 1.3 times greater (2.30 ± 0.06 vs.
    1.76 ± 0.04 Favge/ Wb) and minimum tsw that were
    similar (+8%). We conclude that human runners
    reach faster top speeds not by repositioning
    their limbs more rapidly in the air, but by
    applying greater support forces to the ground. or1=Weyand&searchid=1&FIRSTINDEX=0&sortspec=releva nce&resourcetype=HWCIT