Task-oriented control of muscle coordination during cycling.

Area of Science:

• Biomechanics
• Human Physiology
• Motor Control

Background:

• Muscle activation patterns exhibit variability during cyclic movements like cycling.
• Understanding this variability is crucial for optimizing performance and preventing injury.

Purpose of the Study:

• To investigate how different biomechanical constraints, specifically cycling power output, affect muscle activation variability.
• To analyze the structure of muscle activation variability in lower limb muscles during cycling.

Main Methods:

• Fifteen male athletes performed cycling at 150 W and 300 W while surface electromyography (sEMG) of seven lower limb muscles was recorded.
• Wavelet transformed sEMG signals underwent principal component analysis (PCA) to quantify muscle activation variability.
• Relative variability (RV) was calculated, and principal angles were used to compare muscle coordination patterns between power conditions.

Main Results:

• Muscle activation variability was lower at higher cycling power (300 W) compared to lower power (150 W).
• Variability was consistently smaller for lower-ordered eigenvectors, indicating structured aspects of muscle coordination.
• A small average principal angle (0.4) suggested similarity in the underlying muscle coordination subspaces between the two power conditions.

Conclusions:

• Cycling at higher power imposes constraints that lead to more structured and less variable muscle activation patterns.
• This suggests a shift towards a more specific and precise muscle coordination strategy under increased task demands.
• The findings support the minimum intervention principle, where task constraints dictate muscle activation patterns.