There are some full and half truths printed above.
1. In short, the lengthening of a muscle fiber under
load IS more traumatic and thereby damaging. The
degree of recovery has to do with rest, diet, and all
factors discussed here before ad infinitum. However,
no reasonable athlete could perform well by training
with negative motions only. Therefore the need for
concentric contraction work for coordination. In
practice, the two motions almost always come together
to provide a synergistic effect and a more natural
movement profile. Training too often with negative
motions ( using heavier weights than possible in
concentric work or after failure in conjunction with
concentric work ) has been shown to be a route to
overtraining.
2. While the latissimus may indeed function in a
greater range of motion when the narrow grip is used,
it is important to attempt to place the body in
typical anatomical positions when weight training, and
recruit muscle from typical postures: thus the limited
utility of "isolation" exercises that do not coordinate
the muscular action with the rest of the body
ultimately producing unusable strength and size out of
proportion to function.
3. While the biceps does assist in flexing the elbow
when supinated, it is still responsible for only 30%
of the effort. Personal testimony: I was able to do
pullups with a totally detached distal tendon of my
left biceps, so only the brachialus did the work.
4. The pullup performed with the hands pronated has a
greater benefit for many sport-specific movements.
Think of the natural motion of climbing, for instance.
5. Please remember that we are not talking
bodybuilding here, but training for martial arts. The
balances of strength/muscular development requirements
are not necessarily similar!!
Lee
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