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

INTRODUCTION: 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. METHODS: 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. RESULTS: : 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. CONCLUSION: 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.