Effect Of Handgrip Training With Blood Flow Restriction On Resting Blood Flow And Vascular Resistance

Muscle adaptations (changes in muscle size and strength) with low-intensity exercise paired with blood flow restriction are known to increase to a greater extent than the same exercise without the restriction. However, changes in vasculature associated with the exercise protocol is not fully understood. In addition, some have hypothesized that repeated bouts of blood flow restriction might be detrimental to vascular health and function. PURPOSE: To evaluate changes in resting forearm blood flow following low intensity handgrip training with and without blood flow restriction. We also compared this to high intensity handgrip training. METHODS: 179 participants (18-35 years) completed this 6-week study. Participants were randomly assigned to one of the four conditions: high-intensity (HI; n = 47; maximum voluntary contraction (100% MVC); 5 sec/set; 4 sets/session), low-intensity (LI; n = 47; 30% MVC; 2 min/set, 4 sets/session), low-intensity with blood flow restriction (LI-BFR; n = 41; 30% MVC, 50% arterial occlusion pressure [AOP]; 2 min/set, 4 sets/session), or non-exercise control (CON; n = 44). Participants came in for 3 visits/week (excluding CON) to perform the exercise with their dominant arm under their assigned condition. Before and after the training period, each participant had their resting limb blood flow measured in their dominant forearm. Changes in resting limb blood flow were compared using a Bayesian ANCOVA. The pre-value served as the covariate. Changes are noted as means (SD). RESULTS: The ANCOVA found no evidence for changes in resting forearm blood flow (BF10: 0.06). Pre-post changes in blood flow were 0.08 (0.98), 0.26 (0.67), 0.34 (0.96), and 0.03 (0.76) ml·min-1·100 ml-1 for the CON, LI, LI-BFR, and HI groups, respectively. There were also no changes when mean arterial pressure was divided by blood flow and represented as forearm vascular resistance (BF10: 0.08). Pre-post changes in forearm vascular resistance were 0.04 (14), -2.9 (12.9), -5.4 (18) and -2.7 (14) mmHg per flow for the CON, LI, LI-BFR, and HI groups, respectively. CONCLUSION: Low intensity exercise with BFR did not impede or improve blood flow. The beneficial effects to vascular health may only be observed with higher pressures not used in this study (e.g. 80% AOP). This requires further study.