The kinetic response of microvascular oxygen extraction in the exercising muscle, as estimated via the deoxyhaemoglobin (Hb) signal of near infrared spectroscopy (NIRS) to constant workload exercise has been well characterised (DeLorey et al, 2003; Grassi et al, 2003; Ferreira et al, 2005). In contrast the typical response to incremental exercise is less well-defined despite a number of authors utilising the “inflection” point of Hb as a marker of anaerobic threshold (Bhambani, 2004). However recent data suggest that the rate of increase of workload during exercise may have some bearing on the nature of Hb kinetics during this type of exercise (Wang et al, 2006). The purpose of the present study was therefore to investigate the response of Hb to ramp exercise during a slow (SR) and fast (FR) rate of increase of workload. Following approval from London South Bank University Research Ethics Committee, 7 young healthy male (recreational athletes) subjects completed a ramp test (40 W / min, FR) to exhaustion and an incremental exercise test (SR) consisting of 2 min stages at 30, 40, 50, 60, 70 & 80 % VO2max (mean incremental rate ~16 W / min), on a cycle ergometer. During each test the oxygenation status of the vastus lateralis was determined via NIRS. The inflection point of the Hb data was evaluated by iteratively fitting combinations of 2 regression lines to yield the lowest sum of squared residuals. The regression line gradient prior to the inflection point (S1) was greater than the regression line gradient after the inflection point (S2) during FR for all subjects. In contrast during SR, the gradient for the S1 regression line was less than S2 for 5 out of 7 subjects. There was a significant correlation between the power output at the inflection point during SR and FR (r=0.84, p<0.01), however the average power output at the inflection point was significantly higher in the FR (219 ± 11 W) compared to the SR (125 ± 11 W), p<0.01. The present data demonstrate that the rate of increase of workload during exercise impacts upon the time-course of muscle deoxygenation as measured via NIRS. Furthermore, the use of the inflection point of Hb as a proxy for the anaerobic threshold should be treated with caution.