'''Deconditioning''' is adaptation of an organism to less demanding environment, or, alternatively, the decrease of physiological [[Physiology]]cal adaptation to normal conditions. Decondition may result from decreased physical activity, prescribed bed rest, orthopedic casting, paralysis, aging, etc. A particular interest in the study of deconditioning is in aerospace medicine, to diagnose, fight, and prevent adverse effects of the conditions of space flight.
Deconditioning due to decreased physical effort results in muscle loss, including heart muscles.