Atrophy: gradual decline in effectiveness or vigor due to underuse or neglect I type this currently hobbled on a walking boot from a torn calf muscle. The only cure for this particular injury is plenty of rest and easing back into activity. One interesting observation is how quickly the muscles surrounding my actual injury have atrophied after only a short period of rest. The phrase “use it or lose it” is often said but rarely understood until the effects are extreme and impossible to ignore.