I’ve been continuing the anatomy studies in respect of Yoga and some fascinating things have been uncovered, the latest being the challenges of doing Yoga in space, and in fact the challenges of just moving in space. Googling around I’m surprised I can’t find much material on the subject of how the body adapts to moving its muscles in space.
First a simple exercise – hold your arm straight out at 90 degrees. Now slowly bend at the elbow and bring your hand up until it is pointing upwards. During that move the main muscle doing the work should have been the biceps, contracting to bring the hand and lower arm upwards. Now bring the hand to the shoulder (while keeping the upper arm straight out). The muscle doing that work should have been the triceps – the muscle lengthening while ‘contracting’ i.e. ‘pulling’ against the force of gravity to slow and control the hand’s descent (the scientific/medical term for that is ‘eccentric contraction’ (ref: http://muscle.ucsd.edu/musintro/contractions.shtml).
So what happens if you do that movement in space? Everything is different, that’s what! It looks like there would certainly be no switch-over from the biceps to the triceps at the point where the hand is pointing straight upward. I imagine that the biceps would continue it’s ‘normal’ concentric contraction unti the hand was near the shoulder and then maybe the triceps steps in with eccentric contraction against the momentum of the upper arm coming in towards the shoulder to slow it down.
The whole practice of Yoga would have to be different in zero-G. Some asasas e.g. the shoulder stand (salamba sarvangasana) would lose their meaning without gravity to work against, but I’m sure dedicated Yogis would come up with a host of zero-G friendly alternatives – what do you think?