REF-596 · Piasecki, Ireland, Piasecki, Stashuk, McPhee et al., 2018 · The Journal of Physiology, · Paper · PubMed
Sarcopenia is partly neurogenic: motor-unit numbers fall with age, and the failure of surviving units to enlarge (reinnervate) distinguishes sarcopenic from non-sarcopenic older muscle
Participants
n=143 men: young (48), non-sarcopenic old (13), pre-sarcopenic (53), sarcopenic (29). Vastus lateralis.
Protocol
Cross-sectional comparison of four groups of men: young (n=48), non-sarcopenic old (n=13), pre-sarcopenic (n=53) and sarcopenic (n=29) (from the abstract)
Motor unit potentials isolated from intramuscular and surface EMG recordings (the abstract names the vastus lateralis); motor unit number and size compared between groups
Key Findings
Motor-unit numbers were reduced in all older groups vs young men (all P < 0.001) — progressive motor-neuron loss.
Non-sarcopenic and pre-sarcopenic older men had larger motor-unit potentials than young men (P = 0.039 and 0.001) — surviving units enlarge via collateral reinnervation of denervated fibres.
Sarcopenic older men did NOT show this enlargement (P = 0.485 vs young) — the failure of compensatory reinnervation, not neuron loss alone, distinguishes sarcopenic from pre-sarcopenic muscle.
Motor-unit remodelling occurs relatively early in ageing, exceeds the loss of muscle mass and precedes sarcopenia.
Not from this paper: the preferential vulnerability of the largest/fastest (Type II) units is a claim from the wider ageing literature, not this study; what the base does carry is that peak power declines faster than aerobic capacity with age (REF-349).
Practical Application
In 143 men, every older group had fewer motor units than the young, but only the non-sarcopenic and pre-sarcopenic older men had enlarged the surviving units; the sarcopenic men had not — muscle loss in ageing tracks the failure to reinnervate, not just neuron loss.
Inference, not tested: treat resistance + explosive training as neuroprotective — heavy loads (high-threshold recruitment) + high-velocity intent keep the at-risk units active. The study measured motor units, not training responses.
Prioritize early — remodelling starts before sarcopenia, so the window to keep compensating is before mass is lost.
Supports the base's "include explosive/power work, not just endurance" advice for masters (REF-349); inference, not tested here: strength tests can look preserved while velocity/power erodes.
Limitations
Cross-sectional (no within-person tracking); MU number *estimates*; male, single muscle; non-athletes → likely worst-case (trained masters may reinnervate better); no training arm, so the "neuroprotective" application is inference.
How this entry was checked and changed
Why this level
(mechanistic, controlled comparison)
Content correction 2026-09-27
Added the Participants section (n=143; 48/13/53/29 per group) and the abstract's P-values; entry previously carried no n.
"Type II units preferentially vulnerable → power lost faster than strength" labelled as not from this paper; the REF-349 cross-reference now states what REF-349 actually says (power declines faster than aerobic capacity).
Lead line was house advice ("treat training as neuroprotective") -> now the study's finding; training application labelled inference. Tier 1-2 -> Tier 0-1 (non-athletes).
2026-09-28: added Protocol from the abstract (Europe PMC/PubMed PMID 29527694).
2026-09-28: PMID 29406601 belonged to an unrelated paper; replaced with 29527694, the PubMed record for this entry's own DOI.