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Intrinsic Motoneuron Excitability Differentiates Sarcopenic, Nonsarcopenic and Athletic Ageing Phenotypes
Lucas B R Orssatto1,2, David Scott2,3, Brian C Clark4,5
1Centre for Sensorimotor Performance, School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia.
Journal of Cachexia, Sarcopenia and Muscle
|November 26, 2025
Summary
Reduced intrinsic motoneuron excitability contributes to sarcopenia and physical decline in older adults. Exercise may preserve this excitability, offering a target for interventions to restore neuromotor function.
Area of Science:
- Neuromuscular physiology
- Gerontology
- Exercise science
Background:
- Sarcopenia's physical decline mechanisms are unclear, with neural factors like motoneuron excitability gaining attention.
- Reduced intrinsic motoneuron excitability may drive age-related weakness and mobility loss.
Purpose of the Study:
- To investigate differences in intrinsic motoneuron excitability among sarcopenic older adults, controls, and master athletes.
- To determine the relationship between these excitability differences and physical function.
Main Methods:
- Recruited 56 older adults (sarcopenic, controls, master athletes).
- Recorded high-density electromyography (HD-EMG) during isometric contractions.
- Analyzed motor unit discharge properties using paired motor unit analysis to calculate delta frequency (ΔF) as a measure of intrinsic motoneuron excitability.
Main Results:
- Sarcopenic adults showed significantly lower strength and physical function compared to controls.
- Intrinsic motoneuron excitability (ΔF) was substantially reduced in sarcopenic individuals across all intensities.
- Master athletes exhibited preserved or enhanced excitability at higher intensities compared to controls, correlating with better physical function.
Conclusions:
- Reduced intrinsic motoneuron excitability is a key feature of sarcopenia in older adults, impacting functional capacity.
- Long-term exercise practice preserves motoneuron excitability, especially during demanding tasks.
- Intrinsic motoneuron excitability is a potential therapeutic target for sarcopenia interventions.
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