DETRAINING: Two Weeks of Reduced Activity Decreases Leg Lean Mass and Induces "Anabolic Resistance" of Myofibrillar Protein Synthesis in Healthy Elderly
During the period of quarantine in 2020 I was investigating the rate of detraining and the impact of reduced training load. This study looked at age-related muscle atrophy with the hypothesis that "during periods of muscle disuse, muscle protein synthesis is blunted, and muscle atrophy occurs in young and old". In particular the authors investigated "the impact of a short reduction in physical activity on muscle protein metabolism in older adults".
The methodology involved a 14-day period of reduced daily steps hoping to determine the impact on either a fasted and fed-state rate of myofibrillar protein synthesis (MPS). The results showed that:
Leg fat-free mass was reduced by approximately 3.9%. Postabsorptive insulin resistance was increased by approximately 12%, and postprandial insulin sensitivity was reduced by approximately 43% after step reduction. Postprandial rates of MPS were reduced by approximately 26% after the intervention, with no difference in postabsorptive rates.
14 days of reduced steps in older adults induces small but measurable reductions in muscle mass that appear to be underpinned by reductions in postprandial MPS and are accompanied by impairments in insulin sensitivity and systemic inflammatory markers and postprandial MPS.
PRACTICAL TAKE AWAY - as little as 14 days of reduced activity has an impact on older adults. Therefore it would be valuable to include some exercise and training even in a post-season break rather than having a period of complete rest.