Muscle fatigue, pedalling technique and the slow component during cycling.

Abstract

Above the first lactate threshold, the steady-state is delayed or prevented due to the slow component ( ). 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 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 , 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 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 , although there was large interindividual variability for all the reported correlations. Considering the heterogeneity in the data, it is difficult to determine therelative impact of pedalling technique adjustments on overall, but the present study opens the possibility that in some cases, increases in secondary to technical adjustments may be 'superimposed' on the underlying .