The purpose of this study was to examine the metabolic and cardiovascular response to exercise without (CON) or with (BFR) restricted blood flow to the muscles. Ten young men performed upright cycle exercise at 20, 40, and 60% of maximal oxygen uptake, VO₂max in both conditions while metabolic and cardiovascular parameters were determined. Pre-exercise VO₂ was not different between CON and BFR. Cardiac output (Q) was similar between the two conditions as a 25% reduction in stroke volume (SV) observed in BFR was associated with a 23% higher heart rate (HR) in BFR compared to CON. As a result rate-pressure product (RPP) was higher in the BFR but there was no difference in mean arterial pressure (MAP) or total peripheral resistance (TPR). During exercise, VO₂ tended to increase with BFR (~10%) at each workload. Q increased in proportion to exercise intensity and there were no differences between conditions. The increase in SV with exercise was impaired during BFR; being ~20% lower in BFR at each workload. Both HR and RPP were significantly greater at each workload with BFR. MAP and TPR were greater with BFR at 40 and 60% VO₂max. In conclusion, the BFR employed impairs exercise SV but central cardiovascular function is maintained by an increased HR. BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VO₂max; probably indicated by a higher energy supply and RPP. When incorporating BFR, HR and RPP may not be valid or reliable indicators of exercise intensity.

• Blood flow reduction (BFR) employed impairs stroke volume (SV) during exercise, but central cardiovascular function is maintained by an increased heart rate (HR).

• BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VOmax;

• Probably indicated by a higher energy supply (VO) and rate-pressure product (HR x systolic blood pressure).