"Contractile proteins" refers to a group of proteins in our muscles that are responsible for the contraction and relaxation of our muscles, allowing us to move and perform physical activities. Full definition
The theory is that quercetin's capacity to reduce free radical damage may prevent damage to the membranes that surround mitochondria and reduce injury to contractile proteins in muscles that are brought on by exercise. (cathe.com)
«When your body is forced to adapt to the increased demands of a heavier weight, it responds by building more contractile proteins within the muscle, which increases muscle density and muscle tone (myogenic tone).» (womenshealthandfitness.com.au)
The third method is repeat effort — when we do something repeatedly, we increase contractile proteins within the muscles, which increases force output. (mindbodygreen.com)