Local muscle oxygen consumption related to external and joint specific power

The purpose of the present study was to examine the effects of external work rate on joint specific power and the relationship between knee extension power and vastus lateralis muscle oxygen consumption (mVO2). We measured kinematics and pedal forces and used inverse dynamics to calculate joint power for the hip, knee and ankle joints during an incremental cycling protocol performed by 21 recreational cyclists. Vastus lateralis mVO2 was estimated using near-infrared spectroscopy with an arterial occlusion. The main finding was a non-linear relationship between vastus lateralis mVO2 and external work rate that was characterised by an increase followed by a tendency for a levelling off (R2 = 0.99 and 0.94 for the quadratic and linear models respectively, p < 0.05). When comparing 100 W and 225 W, there was a ∼43 W increase in knee extension but still a ∼9% decrease in relative contribution of knee extension to external work rate resulting from a ∼47 W increase in hip extension. When vastus lateralis mVO2 was related to knee extension power, the relationship was still non-linear (R2 = 0.99 and 0.97 for the quadratic and linear models respectively, p < 0.05). These results demonstrate a non-linear response in mVO2 relative to a change in external work rate. Relating vastus lateralis mVO2 to knee extension power showed a better fit to a linear equation compared to external work rate, but it is not a straight line.