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PubMed · 42520337

Age-related differences in motor unit behaviours and maximal strength: A systematic review and meta-analysis.

Dagnew Getnet Adugna·Simon Walker·Oliver Hayman·Yibeltal Yismaw Gela·Chu Gan·Dawson J Kidgell
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Abstract

Ageing is associated with a decline in strength; however, the neural mechanisms underpinning these changes remain poorly understood. Motor unit discharge rate (MUDR) and recruitment threshold (MURT) regulate the magnitude of motoneuron output through rate coding and orderly recruitment, while discharge rate variability (MUDRV) reflects the steadiness of motoneuron output. Yet, age-related differences in these properties remain inconsistent across the literature. Therefore, this systematic review and meta-analysis quantified age-related differences in motor unit behaviours and their contribution to maximal isometric strength. Electronic databases (Medline, Embase, Scopus, PsycINFO, Ovid Emcare, CENTRAL, and Web of Science) were searched up to May 2025, yielding 1493 records; of these, 48 studies met the inclusion criteria. Standardised mean differences (SMDs) were calculated using random-effects models to compare older and younger adults, and methodological quality was assessed using the AXIS tool. Older adults exhibited markedly lower maximal strength than younger adults (SMD = -1.01; 95% CI -1.22, -0.79). MUDR was lower in older adults across all contraction intensities, with greater reductions at high forces (> 60% maximal voluntary contraction (MVC): SMD =&#x202f;-0.65; 95% CI -0.96, -0.34) compared to low forces (< 30% MVC: SMD = -0.34; 95% CI -0.50, -0.18). Discharge rate variability was greater (SMD = 0.44; 95% CI 0.15, 0.72), whereas recruitment thresholds relative to MVC were lower (SMD = -0.42; 95% CI -0.80, -0.03) in older adults. Collectively, these findings suggest that age-related alterations in motor unit discharge behaviour may contribute, at least in part, to reduced maximal strength in older adults.

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AgingHumansMuscle StrengthMotor NeuronsRecruitment, NeurophysiologicalMuscle, SkeletalAgedIsometric ContractionAgeingElectromyographyMaximal strengthMotor unit discharge ratesMotor unitsRecruitment thresholdsJournal ArticleSystematic ReviewMeta-AnalysisReview

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Dagnew Getnet Adugna, Simon Walker, Oliver Hayman, Yibeltal Yismaw Gela, Chu Gan, Dawson J Kidgell. 2026-07-25. Age-related differences in motor unit behaviours and maximal strength: A systematic review and meta-analysis.. https://doi.org/10.1016/j.neurobiolaging.2026.07.008

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Aged subjectAgeing subjectAging subjectElectromyography subjectHumans subjectIsometric Contraction subjectJournal Article subjectJournal Article; Systematic Review; Meta-Analysis; Review resourceMaximal strength subjectMeta-Analysis subjectMotor Neurons subjectMotor unit discharge rates subjectMotor units subjectMuscle Strength subjectMuscle, Skeletal subjectSystematic reviews study

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