Muscle disuse atrophy is greater in young compared with elderly individuals

Abstract

It is currently unclear whether elderly individuals are more or less susceptible to muscle disuse atrophy compared with young. Here, we compared the magnitude of muscle disuse atrophy between young and elderly subjects. Twelve healthy young (age 23±2 y) and 11 healthy elderly (age 69±3 y) men were subjected to a 5 day period of one‐legged knee immobilization by means of a full leg cast.Three days prior to and immediately after the immobilization period, single slice CT scans and DXA scans were performed to determine quadriceps cross sectional area (CSA) and leg lean mass, respectively. In addition, muscle biopsies were collected to assess myocellular characteristics (analyses ongoing) and 1RM tests were performed to determine muscle strength. Quadriceps CSA decreased with immobilization in both groups (P<0.001 over time), but to a greater extent in the young (−3.5±0.5 % in young vs −1.1±0.6 % in old, P<0.05 between groups). Leg lean mass declined by 1.4±0.7 % with immobilization in young subjects (P=0.07) while no change was detected in the elderly. Strength was reduced to the same extent in young and old after 5 days (−9.0±2.2 % and −7.6±3.7 % respectively; both P<0.01). We conclude that 5 days of muscle disuse leads to significant muscle atrophy and a substantial decline in muscle strength in both young and old individuals. However, the disuse‐induced loss of muscle mass is greater in young compared with elderly individuals.