Abstract
The purpose of this study was to investigate effect of high intensity bicycle training during 6 deg head-down tilt bed rest on muscle function and volume. Ten healthy men were divided into either two groups: countermeasure group (CM, n = 5) and control group (Cont, n = 5). The CM group performed two sessions centrifuge-induced artificial gravity with bicycle exercise training consisted of two sessions (20 min per session, 40 min total) during bed rest period. First session was 0.8-1.4 Gz in supine position with a constant exercise intensity (60 W). Second session was 0.3 Gz in supine position with an interval exercise protocol (40% to 80% of heart rate maximum). Before and after the bed rest period, maximum voluntary contraction (MVC) during knee extension, muscle volume of the thigh, muscle functional MRI (mfMRI) and EMG of the quadriceps femoris during fatiguing isotonic knee extension. CM subjects showed no change in MVC (525 to 485 N, P = 0.31), however the Cont group demonstrated significant change in MVC after bed rest (593 to 457 N, P = 0.008). Muscle volume of the knee extensors, knee flexors, and adductors of the CM group was unchanged, whereas muscle volume of the knee extensors of the Cont group decreased by 9% (P = 0.02). There was no significant change in exercise-induced mfMRI signal change and EMG activity of the knee extensors for both the CM and Cont groups. These results suggested that short-arm centrifuge with high intensity bicycle training would be effective for maintain of function and volume in skeletal muscle. [Jpn J Physiol 54 Suppl:S45 (2004)]
