Youths are less susceptible to exercise-induced muscle damage than adults; a systematic review with meta-analysis

Purpose; This meta-analysis aimed to 1) provide a comparison of peak changes in indirect markers of EIMD in youths versus adults and 2) determine if the involved limb moderated this effect. Method; Studies were eligible for inclusion if they 1) provided a human youth versus adult comparison, 2) provided data on muscle strength, soreness or creatine kinase (CK) markers beyond ≥ 24 hours, 3) did not provide a recovery treatment. Effect sizes (ES) were presented alongside 95% confidence intervals. Results; EIMD exhibited larger effects on adults than in youths for muscle strength (ES=-2.01; P<0.001), muscle soreness (ES=-1.52; P<0.001) and CK (ES=-1.98; P<0.001). The random effects meta-regression examined the effects of upper- and lower-limb exercise in youths and adults was significant for muscle soreness (coefficient estimate =1.11; P< 0.001) but not muscle strength or CK (P>0.05). As such, the between-group effects for muscle soreness (ES=-2.10 versus -1.03; P<0.05) were greater in the upper- than lower-limb. Conclusion; The magnitude of EIMD in youths is substantially less than their adult counterparts, and this effect is greater in upper- than lower-limbs for muscle soreness. These findings help guide practitioners who may be concerned about the potential impact of EIMD when training youth athletes.