RESUMO
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., VËO2max) 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 d·wk, 30-min cycling at 40% of VËO2max), RT (n = 10, 4 d·wk, 4 sets of 10 repetitions leg press at 70% of one repetition maximum with 60 s rest) or ET (n = 10, 4 d·wk, 30-min cycling at 70% of VËO2max) for 8 wk. Measures of quadriceps CSA, leg press one repetition maximum, and VËO2max 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 VËO2max, 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 VËO2max 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.