Acute Physiological Responses To Low-intensity Exercise With Different Levels Of Blood Flow Restriction

PURPOSE: External pressure is a key factor in blood flow restriction (BFR) training. Previous studies have used a limited range of occlusion pressures to compare the acute physiological and perceptual responses during leg exercise. The aim of this study was twofold: i) to compare the physiological and perceptual responses of low-intensity exercise (LI) with different levels of BFR, and ii) to compare LI with BFR on the bike with high-intensity (HI) exercise without BFR. METHODS: Twenty-one healthy, moderately-trained male (age: 24.6±2.4 yrs; VO2peak: 47.2±7.0 ml/kg/min, mean±sd) volunteered to perform one maximal graded exercise test on the bike and seven 5-min constant intensity exercise bouts on separate days and in a counterbalanced order. Six bouts were at 40% peak power (Ppeak; LI); one without BFR and five with different levels of BFR (40%, 50%, 60%, 70%, 80% of arterial occlusion pressure, LI-BFR40/50/60/70/80). Finally, they performed one HI bout (70% Ppeak) without BFR. Oxygen uptake (VO2), heart rate (HR), blood lactate (BLa), rating of perceived exertion (RPE), and tissue oxygen saturation (TSI) with near-infrared spectroscopy were recorded. RESULTS: Regardless of pressure, HR, BLa and RPE during LI-BFR were higher compared to LI (p<0.05), and TSI reduction was greater in LI-BFR (LI-BFR40/50/60/70/80: -10.6±3.1%, -10.2±4.0%, -10.1±5.1%, -10.0±4.2%, -11.3±4.9%, respectively) than LI (-6.0±4.2%, p<0.05).The responses of VO2, HR, BLa, RPE and TSI induced by the different levels of BFR applied in LI-BFR were similar. Regardless of pressure, the responses of VO2, HR, BLa and RPE induced by LI-BFR was lower than HI (p<0.05), except for TSI. TSI change was similar between LI-BFR40/50/60/70/80 and HI (LI-BFR40/50/60/70/80 range: -10.0±4.2% to -11.3±4.9%, HI: -11.5±4.5%). CONCLUSION: It appears that BFR equal to 40% of arterial occlusion pressure is sufficient to reduce TSI. This BFR level seems to stress the physiological mechanisms adequately and there is no need for higher external pressure application. This level of BFR can also produce local hypoxia similar to that during HI. Therefore, low-intensity exercise with BFR could be an alternative exercise mode for individuals who are unable to perform high-intensity exercise.