How many studies support Rest Days?

There is no direct meta-analytic literature under the label "rest days," but the closely related question of optimal resistance-training frequency has been studied extensively: multiple meta-analyses find that training a muscle group roughly twice per week produces greater hypertrophy than once weekly, provided total weekly volume is matched, implying that adequate spacing (i. That's backed by 6 published studies in Vitaebase's database, including 5 meta-analyses, the most recent from 2026 -- a modest but real research base.