The American College of Sports Medicine has updated its guidance on resistance training for healthy adults, reporting that resistance training improves muscle strength, hypertrophy, power, muscular endurance, and several measures of physical function, although only a limited number of prescription variables consistently enhance those adaptations.
The new position stand updates the organization’s 2009 recommendations using an overview of systematic reviews of randomized trials in adults aged 18 years and older. Eligible trials included resistance training programs lasting at least 6 weeks and up to 52 weeks and compared resistance training with no exercise or with an alternative resistance training prescription.
Researchers synthesized 137 systematic reviews including more than 30,000 participants. Compared with no exercise, standard resistance training improved strength across 26 reviews including 23,204 participants, with a quality-of-evidence score of 73%. Standard resistance training also improved hypertrophy, power, endurance, contraction velocity, gait speed, balance, chair stand performance, timed up-and-go, and multicomponent physical function.
Several nontraditional approaches also showed benefit compared with no exercise. Circuit training, elastic band training, home-based training, and velocity-based training improved strength. Circuit training and elastic band training also improved hypertrophy. For performance outcomes, jumping performance was improved with eccentric flywheel training and velocity-based training.
Among prescription variables, strength was enhanced by training at least 2 sessions per week, using loads of at least 80% of one-repetition maximum, performing 2 to 3 sets per exercise, using a full range of motion, and placing exercises at the beginning of a training session. Eccentric flywheel resistance training also enhanced strength compared with standard resistance training.
By contrast, strength was not consistently affected by training to fatigue or failure, machine vs free-weight use, contraction speed, rest intervals, time under tension, blood flow restriction, or periodization. Evidence was also insufficient for some comparisons, including unstable surface training, autoregulation, and some concurrent training questions.
For hypertrophy, researchers found that resistance training improved muscle size, including with circuit and elastic band programs. Among prescription variables, hypertrophy was enhanced by higher weekly volume and by eccentric-only compared with concentric-only contractions. Higher volume of at least 10 sets per muscle group per week was associated with greater hypertrophy.
Hypertrophy was not consistently affected by frequency when total training volume was equated, and it was also not consistently affected by load, training to failure, time under tension, power training techniques, periodization, or exercise order.
Power also improved with resistance training. Compared with standard resistance training prescriptions, power was enhanced by moderate loads of 30% to 70% of one-repetition maximum, low-to-moderate volume of 24 or fewer total repetitions across sets, Olympic-style weightlifting, and power training techniques emphasizing a fast concentric phase.
Physical function findings were more nuanced. Compared with no exercise, resistance training improved gait speed, balance, chair stand performance, timed up-and-go, and multicomponent function. Researchers found insufficient data to determine whether resistance training improved stair climbing performance. They also found insufficient data to determine whether standard resistance training improved walking performance compared with no exercise, although walking performance was enhanced by power training techniques when different resistance training prescriptions were compared.
The review was prospectively registered and conducted in alignment with the Preferred Reporting Items for Overviews of Reviews. Searches were conducted across Ovid MEDLINE, Ovid Emcare, Ovid Embase, the Cochrane Database of Systematic Reviews, EBSCOhost SPORTDiscus, and Web of Science through October 2024.
Included reviews were assessed with the AMSTAR tool, and scores ranged from 1 to 9 out of a possible 11. Researchers also evaluated overlap of primary studies using the corrected covered area method and found moderate overlap for strength outcomes.
The researchers noted several limitations. As an overview of reviews, the analysis provides pooled, group-level evidence and does not establish the comparative effectiveness of specific training programs. Much of the evidence came from adults with limited training experience, and many randomized trials in the field were small or had methodological limitations. Evidence was also limited for some outcomes, including the Short Physical Performance Battery.
Even so, the position stand emphasized that resistance training programs should be individualized and that clinically meaningful benefits can be achieved through a range of approaches, including home-based and lower-dose programs.
“Healthy adults should perform progressive RT, with variable prescription consistent with our findings, to improve muscle function, size, and physical performance,” the researchers wrote.
Disclosures: No specific source of funding was used for this work. Brad J. Schoenfeld formerly served on the scientific advisory board for Tonal Corporation. No other authors reported conflicts relevant to this work.