Author(s): KE, S., XIAOLEI, J., Institution: BEIJING INSTITUTE OF SPORTS SCIENCE, Country: CHINA, Abstract-ID: 861

INTRODUCTION:
It has been suggested that blood flow restriction combined with endurance training can improve aerobic capacity. But in those studies, the magnitude of improvement in aerobic capacity, the type of intervention, the participants and other factors varied. Blood flow restriction leads to greater metabolic stress on local muscles, but there have been few studies on the effects of local muscle physiological indexes. The aim of this study was to discover the changes of oxygen saturation（rSO2） of lower limb muscles during moderate and low intensity endurance exercise with blood flow restriction, and to explore the mechanism of blood flow restriction in improving aerobic capacity.
METHODS:
Eight young male rugby players performed ergometer cycling at 40% of maximum aerobic intensity in two exercise, one with lower extremity blood flow restriction（BFR）and one without(CON). Each exercise includes three 5-min sets with 2 min interval, and the interval between BFR and CON condition was more than 48h. Another eight subjects performed the same exercise at 75% of maximum aerobic intensity. To restrict the blood flow，the subject wear a 5cm wide inflation band at the base of each thigh for a binding pressure of 40mmHg and an inflation pressure of 200mmHg. The rSO2 of the muscles in the middle front of left thigh pre-and in the last 10s of each set（POST） were recorded, and the heart rate and blood lactic acid were recorded immediately post exercise. The paired T-test was performed between BFR and CON condition at each intensity, pre- and post- exercise. Repeated measurement ANOVAs were performed among the three sets.
RESULTS:
At 40% of the maximum aerobic intensity, there was no difference in muscle rSO2 between BFR (the 3rd set: PRE: 59.1±3.22%, POST: 57.1±3.76%) and CON (the 3rd set: PRE: 60.8±2.57%, POST: 59.8±2.14%)(P>0.05), and no difference among the three sets (P>0.05). Only in the 3rd set, the heart rate of BFR（135.7±12.83 bpm）was higher than that of CON (129.4±8.31 bpm) (P<0.05). There was no difference in blood lactate concentration between BFR（4.4±1.2mmol/l）and CON (4.2±1.0mmol/l) post exercise (P>0.05).
At 75% maximum aerobic intensity, the muscle rSO2 of both conditions decreased during exercise (P<0.05).The muscle rSO2 post exercise of BFR was lower than CON in 2 sets（2nd set:BFR:48.8±4.38% vs CON:51.8±2.25%; 3rd set: BFR: 46.8±4.21% vs CON: 50.5±2.23%）(P<0.05). The BFR showed an decrease with the number of exercise sets (P<0.05). The heart rate of BFR was higher than that of CON condition (P<0.05), and showed an increasing trend with the set. There was no difference in blood lactate concentration between BFR（7.8±1.8mmol/l）and CON (7.0±1.5mmol/l) post exercise (P>0.05).
CONCLUSION:
Blood flow restriction did not significantly affect the physiological load of local muscle during short intermittent low-intensity aerobic exercise, but increased the physiological load of local muscle during medium intensity aerobic exercise.