Onset of blood lactate accumulation and peak oxygen uptake during graded walking test combined with and without restricted leg blood flow

The purpose of this study was to compare the peak oxygen uptake (VO 2peak ) and lactate threshold / onset of blood lactate accumulation (LT/OBLA) during an incremental exercise test with and without blood flow restriction (BFR). Six male subjects performed a graded walking test on a treadmill with and without BFR in random order, and oxygen uptake (VO 2 ), minute ventilation (V E ), and blood lactate concentration were measured during each test. During the BFR test, the subjects wore pressure cuff belts on the most proximal portion of each thigh. At a given workload (e.g. during walking at 100 m/min) VO 2 was 17% higher in BFR than in free-flow. Exercise time to exhaustion during BFR was shorter compared with free-flow despite the ratings of perceived exertion being similar between both conditions. Peak heart rate did not reach same level in the BFR test as it did in free-flow, with the heart rate 5 beats lower with BFR. VO 2peak and V E peak were also 17% and 9%, respectively, lower in BFR than in free-flow. Compared with the control, O 2 pulse (an index of stroke volume) was 14% lower in BFR. During BFR, VO 2 at LT and OBLA were lower compared with free-flow. However, percentages of VO 2peak at LT and OBLA were similar between BFR and free-flow. Our results suggest that the BFR-induced decrease in VO 2peak may be associated with reductions in venous return and stroke volume. Additionally, these results suggest that increased muscle fiber recruitment with BFR may relate to the earlier LT/OBLA observed at lower intensities.