Aerobic exercise capacity and muscle volume after lower limb suspension with exercise countermeasure.

Aviation, Space, and Environmental Medicine 81(12):1085 (2010) PMID 21197852

The purpose of the present study was to elucidate the effect of unilateral lower limb suspension (ULLS) on aerobic capacity during one-legged cycle exercise and whether the change in aerobic exercise capacity after ULLS with or without intensive interval training is related to the change in skeletal muscle volume. There were 13 young men who underwent 20 d of ULLS and were divided into 2 groups based on some physical characteristics: the control group (CON; N=7) and the trained group (TRN; N=6). Subjects in TRN underwent interval cycle training on alternate days during ULLS. The respiratory and circulatory responses to one-legged incremental cycling and muscle volume of the thigh were measured before and after 20 d of ULLS. : One-legged peak oxygen uptake (VO2peak) and total muscle volume of the thigh in CON decreased significantly after 20 d of ULLS (-11.0 +/- 3.5% in VO2peak, -6.1 +/- 1.8% in total muscle volume). However, these parameters were maintained in TRN (+0.2 +/- 5.2% in VO2peaka, -1.0 +/- 1.8% in total muscle volume). Circulatory variables at rest and during submaximal exercise were unchanged in both groups after ULLS. Changes in one-legged VO2peak were significantly correlated with change in total muscle volume of the thigh in CON. Our findings indicated that peripheral adaptations after ULLS could relate to the change in aerobic exercise capacity during one-legged exercise. Our results also suggest that intensive interval training prevents ULLS-induced deconditioning of both aerobic exercise capacity and skeletal muscle volume.