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Safe momentum to catch

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  • Safe momentum to catch

    Hi all,
    I'm a trampolining coach looking for a bit of biomech expertise to answer a
    question. First, a bit of background.

    In trampolining 2 or 4 spotters are traditionally placed around a trampoline
    to 'stop a performer falling off'. This goes back to the first days of
    trampolines, in the 1950s. Practical experience tells us that in fact
    spotters seem to do more harm than good, for a variety of reasons, at all
    levels. But there is little objective evidence to support this.

    I was wondering if any studies had been carried out into the catching or
    handling of objects moving at speed. A trampolinist may fall from a CoM 2 -
    8m above floor level, and weigh anything from 30 - 100kg! My quick
    calculation suggests that this suggests a downward velocity of 6.3m/s -
    12.6m/s on contact. This means a range of momentum from 190 - 1260 kgm/s.

    One problem is that it could be (erroneously but believably) claimed that
    spotters are able to assist the spotter without taking the full weight.
    This is not possible as spotters are not fast enough, nor adept enough to do
    so reliably in all but the most trivial situations. However, to counter
    this claim, research into catching, reaction speed, or other similar work
    would be helpful.

    For safety it might be suggested that the spotter should be capable of
    safely taking the performer's entire weight. I can calculate the average
    force needed to slow the performer to a halt on the floor, is there any
    research upon the maximum safe force a human can exert?

    As you can see, my lack of biomech experience is making it difficult to know
    what research I need, but I hope I have given you enough background to make
    some suggestions!!!

    If I get any replies, I will post a summary to this list.


    Richard Ollerenshaw

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