The muscle is activated constantly during walking and running for example; I once strained mine and it took a long time to heal because it fires so frequently.

The muscle is activated constantly during walking and running for example; I once strained mine and it took a long time to heal because it fires so frequently. The point here is that it’s non-trivial to activate it on command while sitting. The special equipment is likely meant to activate the muscle for all users on command, making their research far more reliable.