Our initial search of the databases returned 2979 publications. After removing duplicates, we selected 159 publications based on their titles and abstracts and thoroughly evaluated them. We also identified 42 RCTs cited in previous systematic reviews and meta-analyses; all of these had already been captured in our search. Of the 159 studies screened, 91 were excluded for various reasons (see ESM), whereas the remaining 68 were retained. Figure 1 provides a flowchart of how publications were chosen for our review.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow chart of the inclusion of publications

The principal investigator or corresponding author of eight RCTs was contacted because of incomplete data. After a personal communication, we obtained additional information for only one RCT, which led to the exclusion of seven other publications. Thus, our meta-analysis ultimately included 68 RCTs [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85] with 108 evaluation arms, 39 of which examined the effects of exercise on muscular strength [18,19,20, 24,25,26,27,28,29, 33, 37, 39, 43, 48,49,50,51, 54, 55, 57, 59,60,61,62,63,64,65, 67, 69,70,71, 73, 77, 79,80,81,82,83, 85], 39 on fat-free mass [18, 19, 21,22,23, 30,31,32, 34,35,36,37,38, 40,