If older men in their early 70s lift heavy weights three times a week for four months, they’ll get noticeably stronger and their big muscle fibers will grow bigger.

A randomized controlled trial with 72±5-year-old healthy men assigned to either heavy resistance training (three sessions/week for 16 weeks) or a no-exercise control group, measuring changes in maximal voluntary contraction strength and type II muscle fiber cross-sectional area via muscle biopsy and isokinetic dynamometry as primary outcomes.

A longitudinal cohort study tracking the same group of healthy older men (aged 72±5) before and after 16 weeks of supervised heavy resistance training three times per week, with repeated measures of MVC and muscle fiber cross-sectional area to assess within-subject changes.

A case-control study comparing men aged 72±5 who have been performing heavy resistance training three times weekly for at least 16 weeks (cases) with age-matched sedentary controls, measuring MVC and type II fiber CSA to determine if training is associated with the reported changes.

A rodent study using aged rats (equivalent to 72 human years) subjected to progressive resistance loading three times per week for 16 weeks, measuring maximal force output and type II muscle fiber hypertrophy to model the human claim.

An in vitro study exposing human myotubes derived from older donors to mechanical stretch mimicking resistance training to assess changes in fiber size and contractile protein expression.