Augmented anabolic responses after 8-wk cycling with blood flow restriction

Introduction: Low-intensity endurance training (ET) performed with blood flow restriction (BFR) can improve muscle strength, cross-sectional area (CSA) and cardiorespiratory capacity.Whether muscle strength and CSA as well as cardiorespiratory capacity (i.e.,V˙ O2max) and underlying molecular processes regulating such respective muscle adaptations are comparable to resistance and ET is unknown. Purpose: To determine the respective chronic (i.e., 8 wk) functional, morphological, and molecular responses of ET-BFR training compared with conventional, unrestricted resistance training (RT) and ET. Methods: Thirty healthy young men were randomly assigned to one of three experimental groups: ET-BFR (n = 10, 4 dIwkj1, 30-min cycling at 40% of V˙ O2max), RT (n = 10, 4 dIwkj1, 4 sets of 10 repetitions leg press at 70% of one repetition maximum with 60 s rest) or ET (n = 10, 4 dIwkj1, 30-min cycling at 70%ofV˙ O2max) for 8 wk. Measures of quadriceps CSA, leg press one repetition maximum, and V˙ O2max as well as muscle biopsies were obtained before and after intervention. Results: Both RT and ET-BFR increased muscle strength and hypertrophy responses. ET-BFR also increased V˙ O2max, total cytochrome c oxidase subunit 4 isoform 1 abundance and vascular endothelial growth factor mRNA abundance despite the lower work load compared to ET. Conclusions: Eight weeks of ET-BFR can increase muscle strength and induce similar muscle hypertrophy responses to RT while V˙ O2max responses also increased postintervention even with a significantly lower work load compared with ET. Our findings provide new insight to some of the molecular mechanisms mediating adaptation responses with ET-BFR and the potential for this training protocol to improve muscle and cardiorespiratory capacity.