Concurrent Improvements In Muscle Volume And VO2max In Response To Blood Flow Restricted Cycle Training

A previous study has shown that low-intensity dynamic exercise training with muscular blood flow restriction (BFR) produces muscle hypertrophy and strength gains. PURPOSE: To investigate the concurrent improvements in muscular and cardiovascular fitness in response to a single mode of training, we examined the effects of low-intensity cycle exercise training with and without BFR on MRI-measured muscle size and maximal oxygen uptake (VO2max). METHODS: A group of 19 active young men (mean age 23.0 yr) were allocated randomly into either a BFR-training group (n = 9, BFR-training) or a non-BFR control training group (n = 10, CON-training), both of which trained 3 days/wk for 8 wk. Training intensity and duration were 40% of VO2max and 15 min for the BFR-training group and 50% of VO2max and 45 min for the CON-training group. The BFR-training group wore pressure cuff belts (5 cm wide) on both legs during training, with incremental increases in external compression starting at 160 mmHg and ending at 220 mmHg. During all training sessions, heart rate (HR) was recorded for both groups, and the HRs ranged between 129 and 149 beats/min (50-65% HR reserve, mean 59%) for BFR-training group and between 105 and 141 beats/min (37-46% HR reserve, mean 42%) for CON-training group. Thigh muscle cross-sectional area (CSA) and volume (MV) and isometric knee extension and flexion strength were measured before (pre) and 3 days following the final training session (post). RESULTS: MRI-measured thigh and quadriceps muscle CSA (thigh CSA: pre, 142 cm2; post, 147 cm2) and muscle volume (thigh MV: pre, 3508 cm3; post, 3641 cm3) increased by 3.4-5.1% (P < 0.01) and isometric knee extension strength (pre, 194 Nm; post, 209 Nm) tended to increased by 7.7% (P < 0.10) in the BFR-training group. There was no change in muscle size (-0.1 to 1.6%) and strength (2.0%) in the CON-training group. Significant improvements in VO2max (pre, 2.73 l/min; post, 2.91 l/min; 6.6%) and exercise time until exhaustion (pre, 11.0 min; post, 12.7 min; 15.4%) were observed in the BFR-training group (P < 0.05) but not in the CON-training group (-0.1 and 3.9%, respectively). CONCLUSIONS: The results suggest that low-intensity, short-duration cycling exercise combined with BFR improves both muscle hypertrophy and aerobic capacity concurrently in young active males. Supported in part by JAXA