Acute Cardiovascular And Muscular Response To No-load Exercise With And Without Blood Flow Restriction

Abstract

PURPOSE: To examine acute changes in muscle thickness, isometric strength, and arterial occlusion pressure (AOP) following NO LOAD exercise with and without the application of blood flow restriction (BFR) in the upper body. METHODS: Changes in muscle thickness, isometric strength and AOP were examined following four sets of twenty repetitions of unilateral elbow flexion exercise. Participants performed maximal muscle contractions with no external load throughout a full range of motion with and without the application of a moderate BFR (40% of AOP). Results are displayed as mean (SD). RESULTS: 39 resistance-trained males and females completed the study. For isometric torque there was a condition x time interaction (p = 0.012). The BFR condition had lower isometric torque immediately following exercise [56.07 (17.78) Nm] compared to the control group [58.67 (19.06) Nm]. In addition, both the BFR and control conditions demonstrated a decrease in torque immediately following exercise [mean change = 4.5 (4.5) and 1.82 (4.5) Nm for BFR and control conditions respectively], which remained decreased below baseline 15 minutes post exercise [mean change 2.39 (5.5) and 2.28 (3.19) Nm for BFR and control conditions respectively]. For muscle thickness, there was a main effect for time (p < 0.001). Muscle thickness increased from pre [3.52 (.78) cm] to post [3.68 (.81) cm] exercise and remained increased above baseline 15 min post exercise [3.6 (.80) cm]. For AOP, there was a group x time interaction (p = 0.027). The change in AOP was greater in the BFR group [16.6 (13.42) mmHg] compared to the control group [11.1 (11.84) mmHg]. CONCLUSIONS: NO LOAD exercise with the application of BFR led to greater reductions in isometric torque compared to NO LOAD exercise without the application of BFR. In addition, the application of BFR led to an exaggerated cardiovascular response compared to NO LOAD exercise alone. There were no differences in acute muscle swelling between NO LOAD exercise with and without BFR. These results suggest that the application of BFR to NO LOAD exercise may lead to a greater level of muscle fatigue when performing four sets of twenty maximal repetitions. This is accompanied with an exaggerated cardiovascular response.