View Full Version : Safe momentum to catch

Richard Ollerenshaw
07-09-2001, 08:17 PM
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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