I feel that longer spans shorten the amount of time between the thumb clearing thumb hole and the fingers exiting the ball (the hand is already stretched, so all the pressure is on the fingers, so as soon as the thumb exits, the fingers are going to want to exit as well). With a relaxed span, there is little to no pressure on the fingers. Once the thumb clears, there is more time to build up pressure on the fingers, prior the fingers exiting the ball. As a result, its easier (I feel much easier) to get effort-less revs on a ball with a shorter span. Longer spans tend to make you lift or hit the ball to get revs on it, while shorter spans don't. Click
HERE for an article on the "modern" method of fitting a span. If you have had a stretched span for quite some time, a relaxed span is definitely going to feel different (maybe even hard to get out of the ball). But after bowling it a relaxed span for a while, people tend to start to allow their hand/arm relax and come out of the ball just fine. Of course, this is only a suggestion.. everyone is different and comfort IS the biggest factor (however if your hand is stretched and tight, I'm not sure it can be truly comfortable).
S^2
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