Muscle atrophy is just a state of mind.
Learned from: Kill Bill: Vol. 1 (2003)
Muscle atrophy is medically described as a condition where muscle mass decreases due to a lack of use; it's most commonly caused by being in a comatose state, because the body isn't moving for a significant amount of time.
Though it's a physical ailment that sees muscles literally wasting away, Quentin Tarantino's Kill Bill: Vol. 1 has taught us that it can be cured with the mind. Screw physical therapy and electrical stimulation—just sit around for fifteen hours and try to wiggle your toe. You'll be strong enough to fight bad guys in no time.