The Role Of The Metaboreflex On Cardiovascular Responses To Submaximal Exercise With Blood Flow Restriction

It is unclear how much of the cardiovascular responses during blood flow-restricted exercise are due to the sensory signal from the accumulation of metabolites. PURPOSE: To investigate the role of the metaboreflex in cardiovascular responses to submaximal low-load resistance exercise with different pressures and modes of blood flow restriction. METHODS: Fifty-six adults (33 males; age 22 SD 4) completed six visits. The first visit involved a 1RM test and a local muscular endurance test (2 sets of unilateral knee extension exercise until task failure at a 30% 1RM with 1 min inter-set rest) with the cuff inflated to 80% arterial occlusion pressure (AOP). In subsequent visits, participants performed 1) a time-matched non-exercise control (CON), 2) 70% of the repetitions completed in the endurance test with the cuff continuously inflated to 2) 80% AOP (LL + 80%), 3) 40% AOP (LL + 40%), 4) intermittently inflated to 80% AOP only during exercise (LL + 80%Int), and 5) not inflated (LL), in a randomized order. Three min of post-exercise circulatory occlusion followed by three min of free flow recovery was employed to assess muscle metaboreflex activation. Blood pressure was measured at baseline and at several distinct points into recovery. A linear mixed model was used for analysis. RESULTS: Systolic and diastolic blood pressure increased (LL + 80% > LL + 40% > LL + 80%Int = LL) immediately after exercise in all exercise conditions compared to CON (p < .001). LL + 80% observed the greatest change from CON in both systolic [18 (95% CI: 16, 21) mmHg] and diastolic [15 (95% CI: 13, 17) mmHg] pressure. For comparison, LL had relatively smaller increases over CON in both systolic [10 (95% CI: 8, 13) mmHg] and diastolic [5 (95% CI: 3, 7) mmHg] pressure. The changes from the immediate post-exercise to the end of the circulatory occlusion period did not differ among exercise conditions for systolic or diastolic blood pressure (~5 mmHg decrease). In all exercise conditions, the systolic and diastolic blood pressure decreased (p < .001) and returned to a similar level as CON (~118/70 mmHg) immediately after the cuff deflation. CONCLUSION: Continuous blood flow restriction, especially with higher pressure, accentuates muscle metaboreflex activation, resulting in amplified cardiovascular responses to the submaximal unilateral knee extension exercise.