Ageing is not associated with greater exercise-induced muscle damage or impaired recovery in older adults; a meta-analytical comparison

Anecdotal evidence suggests that ageing is associated with greater symptoms of exercise-induced muscle damage (EIMD) (e.g. reductions in muscle function, increases soreness and circulating creatine kinase [CK]) and impaired recovery. However, the available literature is contrasting and does not appear to support this. Therefore, the aim of this study was to provide a meta-analytical comparison of EIMD symptoms at 24, 48 and 72 hours, and for peak symptoms (i.e. those with the greatest magnitude of change), in younger (e.g. 18 to 25 years) and older adults (e.g. >35 years). Google Scholar, PubMed and Sport Discus were searched from August 2022. Studies were eligible for inclusion if they 1) provided an adult age comparison, 2) provided muscle function (e.g. strength), soreness or CK markers between 24 and 72 hours after muscle damaging exercise, 3) did not provide a recovery treatment or included a treatment free control group, 4) and were performed in humans. An inverse-variance random-effects model for meta-analyses was employed because it allocates proportionate weight to comparisons based on the size of their individual standard errors whilst accounting for heterogeneity across studies. Effects were represented by the standardised mean difference (SMD). Thirty-six comparisons from 34 individual studies were included in the analysis: 27, 21 and 24 for muscle function, muscle soreness and CK, respectively. The main effects for muscle function at 48 hours (SMD = -0.35, Z=-1.74, P<0.05), muscle soreness for all comparisons (SMD range = -0.34 to -0.62, Z range = -2.10 to -5.30, P<0.05) and CK for 24 hour and peak comparisons (SMD = -0.37 and -0.34, Z= -2.82 and -2.68, respectively, P<0.05) indicated greater EIMD symptoms in younger than older. All other comparisons were non-significant (P>0.05). These data suggest that older adults do not experience greater EIMD symptoms or impaired recovery after muscle-damaging exercise. Indeed, there is strong suggestion that older adults experience a reduced magnitude of EIMD symptoms, particularly for muscle soreness. These findings provide insight and encouragement to practitioners who may be concerned about the potential impact of EIMD in older adults specifically.