GLOSSARY

Central fatigue is a reduced ability of the central nervous system to voluntarily activate muscles, causing a fall in force even when the muscle itself could still produce more; it is contrasted with peripheral fatigue (within the muscle).

Possible Mechanisms

• Reduced motor cortex output and corticospinal excitability.
• Inhibitory feedback from muscle group III and IV afferents (sensitive to metabolites) that reduces central drive.
• Neurotransmitter changes: a rising serotonin-to-dopamine ratio and build-up of adenosine and ammonia.
• Rising brain temperature in the heat.
• Falling blood glucose and brain glycogen stores.
• Psychological factors: motivation, perceived effort, and mental fatigue.

Measurement

Interpolated twitch technique: electrical stimulation of the muscle during a maximal voluntary contraction