Influence of exercise during 28 days of bed rest with energy deficit and amino acid supplementation on metabolic profile

Abstract

Muscle loss and metabolic changes occur with disuse [i.e. bed rest (BR)]. We investigated the metabolic profile after 28 days of BR with energy deficit in individuals randomized to resistance exercise with amino acid supplementation (RT, n=24) or amino acid supplementation alone (AA, n=7). We hypothesized that BR would lead to a metabolically unhealthy profile defined by: increased circulating tumor necrosis factor (TNF)‐α, decreased circulating insulin‐like‐growth‐factor (IGF)‐1, decreased HDL‐cholesterol, decreased normal density muscle (NDM) and increased low density muscle (LDM; measured by mid‐thigh computerized tomography). We found a shift toward a metabolically unhealthy profile after BR (compared to baseline) in both groups as shown by decreased HDL levels (AA: 39±4 →32±2 mg/dL, RT: 39±1 →32±1 mg/dL; p<0.001) and LDM (AA: 27±4 →22±3 cm2, RT: 28±2 → 23±2 cm2; p<0.001). A healthier metabolic profile was maintained with exercise, including NDM (AA: 124±6 → 110±5 cm2, RT: 132±3 → 131±4 cm2; p<0.001, time‐by‐group); although, exercise did not completely alleviate the unfavourable metabolic changes seen with BR. Interestingly, both groups had increased plasma IGF‐1 levels (AA: 168±22 → 213±20ng/mL, RT: 180±10 → 219±13 ng/mL; p<0.001) and neither group showed TNFα changes (p>;0.05). We conclude that RT can partially offset the metabolic complications of BR. Support: NSBRI‐NPFR00301 & GCRC M01 RR00