Muscle fatigue, pedalling technique and the V ̇ O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ slow component...

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• The slow component of oxygen uptake (V̇O2slow) emerges above the first lactate threshold, potentially linked to muscle fatigue.
• The role of pedaling technique adjustments in V̇O2slow during fatiguing cycling exercise remains unclear.
• Existing evidence for a causal relationship between muscle fatigue and V̇O2slow is equivocal.

Purpose of the Study:

• To investigate the relationship between muscle fatigue, cardiorespiratory responses, and pedaling technique during fatiguing cycling.
• To explore the contribution of pedaling technique adjustments to V̇O2slow during sustained, high-intensity cycling.

Main Methods:

• Eleven participants completed constant power cycling trials above the second lactate threshold.
• Muscle fatigue assessed via femoral nerve stimulation; cardiorespiratory measures (V̇O2), quadriceps oxygenation, EMG, and pedal forces were recorded.
• Correlations between physiological and mechanical variables were analyzed at group and individual levels.

Main Results:

• Moderate correlations were found between V̇O2slow and quadriceps twitch force (r = -0.51) and muscle oxygenation (r = -0.52).
• Weak correlations were observed between V̇O2slow and EMG amplitude/frequency, and pedaling mechanical variables.
• Significant interindividual variability in correlations suggests heterogeneous responses to fatiguing exercise.

Conclusions:

• Findings align with literature linking muscle fatigue magnitude to V̇O2slow magnitude, but with considerable individual differences.
• The study suggests that pedaling technique adjustments might 'superimpose' increases in V̇O2slow onto underlying fatigue-related changes.
• Determining the precise impact of pedaling technique on V̇O2slow is challenging due to data heterogeneity.