Brain and muscle activity during fatiguing maximum-speed knee movement

Area of Science:

• Neuroscience
• Human Physiology
• Motor Control

Background:

• Mechanisms of motor slowing in upper limbs are known, but less so for lower limbs.
• Lower limb joints have different functional patterns and segment inertia, potentially causing distinct fatigue manifestations.
• Understanding knee joint fatigue is crucial due to its functional importance.

Purpose of the Study:

• To investigate central and peripheral fatigue manifestations during a fatiguing knee maximum movement rate task.
• To measure brain activity, muscle activity, and brain-muscle coupling (corticomuscular coherence) during this task.
• To compare knee joint fatigue with findings from smaller joint (e.g., finger) tasks.

Main Methods:

• Participants performed a fatiguing knee maximum movement rate task.
• Electroencephalography (EEG) measured brain activity.
• Electromyography (EMG) measured knee flexor and extensor muscle activity.
• Corticomuscular coherence assessed brain-muscle coupling.

Main Results:

• Knee movement rate significantly decreased during the task.
• Brain activity decreased initially then plateaued; knee flexor muscle activity continuously declined.
• Corticomuscular coherence decreased for both flexor and extensor muscles.
• Observed changes suggest both central and peripheral fatigue mechanisms.

Conclusions:

• Acute knee fatigue during high-speed movement involves central and peripheral electrophysiological changes.
• Findings include decreased EEG power, increased cocontraction, and impaired brain-muscle coupling.
• These electrophysiological changes in the knee joint differ from those previously reported for smaller upper limb joints.