We hypothesised that the ratio between the increase in oxygen uptake and the increase in work rate (��VO2/��WR) during ramp cycle exercise would be significantly related to the percentage type II muscle fibres at work rates above the gas exchange threshold (GET) where type II fibres are presumed to be active. We further hypothesised that ramp exercise at higher pedal rates, which would be expected to increase the proportional contribution of type II fibres to the total power delivered, would increase the ��VO2/��WR slope at work rates above the GET. Fourteen healthy subjects [four female; mean(SD): age 25(3)years, body mass 74.3(15.1)kg] performed a ramp exercise test to exhaustion (25Wmin1) at a pedal rate of 75revmin1, and consented to a muscle biopsy of the vastus lateralis. Eleven of the subjects also performed two further ramp tests at pedal rates of 35 and 115revmin1. The ��VO2/��WR slope for exercise GET (S1) was significantly correlated with VO2 peak in mlkg1min1 (r=0.60; P0.05), whereas the ��VO2/��WR slope for exercise GET (S2) was significantly correlated to percentage type II fibres (r=0.54; P=0.05). The ratio between the ��VO2/��WR slopes for exercise above and below the GET (S2/S1) was significantly greater at the pedal rate of 115revmin1 [1.22(0.09)] compared to pedal rates of 35revmin1 [0.96(0.02)] and 75revmin1 [1.09(0.05), (P0.05)]. The greater increase in S2 relative to S1 in subjects (1) with a high percentage type II fibres, and (2) at a high pedal rate, suggests that a greater recruitment of type II fibres contributes in some manner to the xs VO2 observed during ramp exercise.