Influence of muscle fibre type and pedal rate on the VO sub(2)-work rate slope during ramp exercise

• Published in: European journal of applied physiology Vol. 91; no. 2-3; pp. 238 - 245
• Main Authors: Jones, Andrew M, Campbell, Iain T, Pringle, Jamie SM
• Format: Journal Article
• Language: English
• Published: 01.03.2004
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-003-0971-7

We hypothesised that the ratio between the increase in oxygen uptake and the increase in work rate ( Delta VO sub(2)/ Delta 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 Delta VO sub(2)/ Delta 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 (25Wmin super(-1)) at a pedal rate of 75revmin super(-1), 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 115revmin super(-1). The Delta VO sub(2)/ Delta WR slope for exercise <GET (S sub(1)) was significantly correlated with VO sub(2) peak in mlkg super(-1)min super(-1) (r=0.60; P<0.05), whereas the Delta VO sub(2)/ Delta WR slope for exercise >GET (S sub(2)) was significantly correlated to percentage type II fibres (r=0.54; P=0.05). The ratio between the Delta VO sub(2)/ Delta WR slopes for exercise above and below the GET (S sub(2)/S sub(1)) was significantly greater at the pedal rate of 115revmin super(-1) [1.22(0.09)] compared to pedal rates of 35revmin super(-1) [0.96(0.02)] and 75revmin super(-1) [1.09(0.05), (P<0.05)]. The greater increase in S sub(2) relative to S sub(1) 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" VO sub(2) observed during ramp exercise.