Research

Mixed

Weakness combined with normal lean mass still carries a high risk of mobility impairment, suggesting that muscle quality (function) is distinct from muscle quantity (mass).

You can have normal muscle size but still be 'weak' and at high risk for mobility issues. This is often due to muscle quality (fat infiltration, nerve function) rather than size. Strength training can improve function even if muscle size doesn't change dramatically.

GoodSupportsHIGH confidence
Men who were weak with normal lean mass had two to nearly five times the odds of incident mobility impairment than those who were not weak with normal lean mass.
Robert R. McLean et al. · The Journals of Gerontology Series A · 2014

Why this rating

Clear statistical association in a large pooled cohort.

Source

Criteria for Clinically Relevant Weakness and Low Lean Mass and Their Longitudinal Association With Incident Mobility Impairment and Mortality: The Foundation for the National Institutes of Health (FNIH) Sarcopenia Project

Robert R. McLean et al. · The Journals of Gerontology Series A · 2014

DOI 10.1093/gerona/glu012

Meta-analysis · 6 studiesCited 464×
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DOI resolved against Crossref · corpus check 2026-06-10

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