Abstract
Above the first lactate threshold, the steady-state V̇O2 is delayed or prevented due to the V̇O2 slow component ( V̇O2SC ). This phenomenon has been associated with muscle fatigue, but evidence for a causal relationship is equivocal. Moreover, little is known about the contribution of pedalling technique adjustments to V̇O2SC during fatiguing cycling exercise. Eleven participants completed constant power trials at 10% above the second lactate threshold. Muscle fatigue was assessed, utilizing femoral nerve stimulation and instrumented pedals, while V̇O2 , quadriceps oxygenation, electromyography (EMG) and pedal force components were measured. Correlations between physiological and mechanical variables were estimated at group and individual levels. Group correlations revealed moderate values for V̇O2SC with quadriceps twitch force (r = -0.51) and muscle oxygenation (r = -0.52), while weak correlations were observed for EMG amplitude (r = 0.26) and EMG mean power frequency (r = -0.16), and with pedalling mechanical variables such as peak total downstroke force (r = -0.16), minimum total upstroke force (r = -0.16) and upstroke index of effectiveness (r = 0.16). The findings here align with prior literature reporting significant correlations between the magnitude of muscle fatigue and that of V̇O2SC , although there was large interindividual variability for all the reported correlations. Considering the heterogeneity in the data, it is difficult to determine the relative impact of pedalling technique adjustments on V̇O2SC overall, but the present study opens the possibility that in some cases, increases in V̇O2 secondary to technical adjustments may be 'superimposed' on the underlying V̇O2SC .