Initially learning to play the Theremin in a sitting position would be the best option at first, instead of standing up and getting tired pretty fast so you end up cutting your practice down in 1/2. Later on, after the technique becomes easier on my hands ( and brain ), perharps then the practice could be done part standing up and sitting down to increase my resistance at standing up for long periods of time.
It is true that, maybe for most of you, standing up is an easy task, but my right knee is in such terrible shape due to an accident that happenend in my youth and 40 years later, it giving me some challenges... But when there is a will, there is a way! The perfect solution is around the corner hiding somewhere... Time for some digging, right?
:)