Abstract

Short periods of bed rest lead to the loss of muscle mass and quality. It has been speculated that dietary feeding pattern may have an impact upon muscle protein synthesis rates and, therefore, modulate the loss of muscle mass and quality. We subjected 20 healthy men (age: 25 +/- 1 yr, body mass index: 23.8 +/- 0.8 kg/m(2)) to 1 wk of strict bed rest with intermittent (4 meals/day) or continuous (24 h/day) enteral tube feeding. Participants consumed deuterium oxide for 7 days before bed rest and throughout the 7-day bed rest period. Prior to and immediately after bed rest, lean body mass (dual energy X-ray absorptiometry), quadriceps cross-sectional area (CSA: CT), maximal oxygen uptake capacity ((V) over dot(O2p)(eak)), and whole body insulin sensitivity (hyper-insulinemic-euglycemic clamp) were assessed. Muscle biopsies were collected 7 days before, 1 day before, and immediately after bed rest to assess muscle tracer incorporation. Bed rest resulted in 0.3 +/- 0.3 vs. 0.7 +/- 0.4 kg lean tissue loss and a 1.1 +/- 0.6 vs. 0.8 +/- 0.5% decline in quadriceps CSA in the intermittent vs. continuous feeding group, respectively (both P 0.05), with no differences between groups (both P > 0.05). Moreover, feeding pattern did not modulate the bed rest-induced decline in insulin sensitivity (-46 +/- 3% vs. 39 +/- 3%; P 0.001) or (V) over dot(O2p)(eak) (-2.5 +/- 2.2 vs. -8.6 +/- 2.2%; P 0.010) (both P > 0.05). Myofibrillar protein synthesis rates during bed rest did not differ between the intermittent and continuous feeding group (1.33 +/- 0.07 vs. 1.50 +/- 0.13%/day, respectively; P > 0.05). In conclusion, dietary feeding pattern does not modulate the loss of muscle mass or the decline in metabolic health during 1 wk of bed rest in healthy men.