These receptors then tell the brain there is a stimulus, and the brain tells the muscle to contract in response. In addition, there are receptors that tell where each joint is located in relation to all the other body parts that help to determine position in space, etc. Their muscles are taut, and they look lean. You can improve your fat to lean body mass ratio, and you can become stronger too. These are under your voluntary control.
Muscle tone occurs at an involuntary level.
Sensory bombardment can effect changes in perception that then lead to changes in efficiency along the neural pathways. But it goes way beyond a couple of hours a week in the gym. Aimed at physiotherapists, has basic background on how hypotonia affects the young child and exercises for pre-walkers. This can be the start of a long, unbroken period of exploration deprivation that may add to existing deficits. It is difficult for the child who cannot move around to develop cognitively.