How would I know what muscles contract and which ones relax during each phase of a particular movement such as walking? I mean for the arms and legs that is pretty easy. I can just feel my own muscle and see if it feels smaller or bigger during each phase to know whether it is contracting or relaxing. However the glutei and abs are also involved in walking. In particular the glutei in the forward movement of the leg and the abs for stability. For me it is not as easy to feel the muscle to know whether it is contracting or relaxing when it comes to the glutei or abs, especially the abs. So how would I know whether the glutei and abs are contracting or relaxing during each phase?