Effect of muscle strength on VO₂ plateau occurrence rate

The purpose of this study was to investigate the plateau occurrence rate in a cycle ergometer VO_2max test in two groups of subjects, one biased toward low muscle strength relative to cardiovascular fitness (low muscle strength/cardiovascular fitness ratio) and the other biased toward high muscle strength relative to cardiovascular fitness. The subjects, 7 collegiate distance runners (DR) and 6 collegiate football linemen (FL), performed a multiple stage cycle protocol ranging in power output from 60 - 484 W. VO₂ was averaged over 15 sec intervals during each stage. Stage VO₂ was recorded as the average of the steady state values on the VO₂/time curve. Each subject performed a VO_2max test that consisted of two parts, a continuous phase and a discontinuous phase. Leg strength was assessed by 1RM leg press using a hip sled. Plateau occurrence rate was not different between groups (6/7 DR and 6/6 FL; p = 0.538). Absolute VO_2max was similar in DR and FL (4.34 ± 0.4 vs. 4.63 ± 0.5 L/min; p = 0.266), relative VO_2max was greater in DR than FL (65.6 ± 5.6 vs. 38.9 ± 5.5 ml/(kg/min); p < 0.001). Absolute leg strength was greater in FL than DR (342.0 ± 36.0 vs. 158.1 ± 31.8 kg; p < 0.001), as was the leg strength to body mass ratio (2.85 ± 0.22 vs. 2.38 ± 0.37; p = 0.034). The leg strength to cardiovascular fitness ratio, expressed in kg/(ml/min), was greater in DR than FL (9.02 ± 2.2 vs. 2.46 ± 2.2; p < 0.001). These data suggest that leg strength does not affect the occurrence rate of a plateau in VO_2max/power output curve.