Authors: Brad S Currier, Jonathan C Mcleod, Stuart M Phillips
This blog summarizes a recent publication in BJSM.
Why is this study important, and what did we do?
The strength and size of muscles are critical for physical function, metabolic health, and healthy aging. Resistance training (a.k.a. strength training or weightlifting) is the most effective way to improve muscle strength and size. Design of resistance training programs involves changing numerous variables, including load (how heavy is the weight being lifted?), sets (how many times is each exercise performed?), how long do I rest, do I lift using free weights or machines and how often should I train each week? The complexity of resistance training may be a barrier that prevents many people from completing this health-promoting form of exercise – by self-report, more than 65% of the population (in the US) does not meet current strength training guidelines.
In our study, we analyzed randomized trials of resistance training to determine the best programs combining different loads, sets, and frequencies of resistance exercise training in healthy adults to improve muscle strength, size, and physical function. Our analysis is the largest analysis of resistance exercise training, comprising over 5,000 participants (nearly half female) from nearly 200 randomized trials. The answers we provide will assist practitioners with unprecedented evidence and the essential variables of resistance training.
How did we go about this?
We used network meta-analysis (NMA) to compare a non-exercising control group with 12 unique resistance training programs, each differing by the load, sets, and/or weekly frequency. The NMA method synthesizes evidence from studies to compare and give you the rank of the studies in order of their effectiveness in promoting strength and muscle gain. We also considered additional factors (e.g., other training variables and participant characteristics) to determine if they influenced our results.
What did we find?
All combinations of load, sets, and weekly frequency improved strength, muscle mass, and physical function compared to the non-exercising control group. Every resistance training program (so long as you stick to it) works! When comparing multiple training programs (i.e., only exercising groups), training programs with heavier loads (loads that you can lift only 3-5 times) were ranked at the top for increasing strength. In contrast, training programs with multiple sets (at least 2-3 sets per exercise) were ranked highest to maximize muscle growth. Neither the age, sex, nor training experience of participants changed these results.
Our results robustly support existing strength training guidelines however, practitioners should note that even strength training below recommended levels can yield substantial benefits. Even the lowest-ranked programs, such as low loads for strength or single sets for hypertrophy, were substantially better than no exercise. While our results provide insight into the ‘optimal’ training programs, given the low participation rates in resistance training, regularly participating in any resistance training program would tremendously benefit adults and, we propose, improve their health.
What are the key take-home points?
All resistance training prescriptions provide substantial strength, muscle growth and physical functional benefits compared to no exercise. The core principle of progression with any form of exercise applies; as soon as something becomes easy, try and do something more.Since most adults do not engage in resistance training, practitioners should prioritize prescribing resistance training and attempting to remove or lower barriers to participation in such programs that promote engagement and adherence so that more individuals experience the benefits of resistance training. For the few individuals already participating in resistance training seeking more specific goals, we found that heavier weights (more load) maximized strength gains, while completing each exercise multiple times (more sets) maximized hypertrophy (size) gains.
Brad S Currier, Jonathan C Mcleod, Stuart M Phillips
Department of Kinesiology, Faculty of Science, McMaster University, Hamilton, Ontario, Canada.
@brad_currier @ MACleod_JC @mackinprof