When it comes to building muscle and strength, you’ll find no shortage of conflicting advice. From the optimal number of sets and reps to whether training to failure is necessary, the finer details of resistance training are constantly debated in forums and comment sections.
But a substantial review of the existing research may help settle some of those arguments.
Published in Medicine & Science in Sports & Exercise, the American College of Sports Medicine’s latest position standbrings together evidence from 137 systematic reviews involving more than 30,000 participants, examining which training variables make the biggest difference to muscle growth, strength and power.
Exercise scientist Dr Mike Israetel has broken down the findings in a recent YouTube video, explaining what the research means for anyone looking to get more from their training.
‘50 participants is already a big study. 30,000 lets us make very strong claims about how it’s best to train and not train,’ he says.
What Did the ACSM Research Review Find?
The review examines the effects of different resistance training protocols on muscle hypertrophy, strength, power and physical performance. Rather than analysing individual trials, the researchers conducted an ‘overview of reviews’, also known as an umbrella review.
‘This study was what’s called an umbrella review, which means it took not individual studies to review, but took systematic reviews themselves and folded them in to one giant analysis,’ explains Israetel.
The aim was to identify which elements of resistance training consistently improve results, and which variables may matter less than previously thought.
The Methods
The researchers analysed 137 systematic reviews involving more than 30,000 healthy adults, drawn from six scientific databases. The studies compared different resistance training approaches over six to 52 weeks, examining variables such as training frequency, volume, load, exercise order and training to failure.
However, much of the evidence came from relatively inexperienced lifters, meaning the findings may not apply equally to advanced lifters.
What Does the Research Say About Building Muscle and Strength?
The review found that resistance training improved muscle size, strength, power and physical performance, but relatively few training variables consistently influenced results.
‘The basics still cover almost all of training,’ says Dr Israetel.
The key findings were:
For muscle growth, higher weekly volumes of at least 10 sets per muscle group proved beneficial.For strength, heavier loads of at least 80% of one-rep max (1RM), training twice weekly and prioritising key lifts early in a session produced better outcomes.For power, moderate loads of 30–70% 1RM, lower training volumes and explosive movements produced better results.Other factors, including training to failure, rep tempo and periodisation, had less consistent effects.
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7 Lessons for Your Own Training1. More Weekly Sets Can Build More Muscle
Training volume was one of the clearest variables associated with muscle growth. The review found that performing at least 10 sets per muscle group each week was more effective for muscle growth than lower volumes.
‘Higher weekly volumes, numbers of sets you do per muscle group cause more growth,’ explains Israetel.
However, increasing volume doesn’t mean gains continue rising at the same rate indefinitely.
‘You go from 5 to 10 sets, you’re going to grow way more. You go from 10 sets to 20 sets, you’re going to grow more, but not as much as from 5 to 10,’ he says.
Israetel suggests increasing weekly sets gradually, provided recovery, sleep and nutrition can support the additional workload. His discussion of 30-plus sets is a coaching interpretation beyond the review’s headline recommendation, rather than a requirement for maximum muscle growth.
2. You Don’t Need to Train to Failure
The review found that reaching failure did not consistently produce better hypertrophy compared with stopping short.
According to Israetel, ‘Going to failure produced no better gains than staying about 1-2 reps shy away from failure in the average situation in your program.’
His recommendation is to begin around three reps in reserve, progressively adding reps or load as training progresses. The takeaway is that your working sets should be challenging, but grinding out every final rep isn’t essential for building muscle.
3. You Don’t Have to Stick to 8-12 Reps
Despite the popularity of the traditional 8-12 rep range for muscle growth, the review found that hypertrophy could be achieved across a broad spectrum of training loads.
‘Roughly even growth is seen from sets of 5 reps that are hard close to failure, sets of 15 reps, and sets of all the way to 30 reps or so,’ says Israetel.
While heavier loads are more effective for maximal strength, lighter weights can still stimulate hypertrophy when sets are sufficiently challenging.
This gives you flexibility to adjust your rep ranges according to exercise selection, joint comfort and fatigue.
4. Training Frequency Matters Differently for Muscle and Strength
The review found that training frequency did not consistently affect muscle hypertrophy when total weekly volume was matched. However, strength was positively influenced by training frequency, with the research supporting at least two sessions per week.
‘There’s no magic gains from higher frequency,’ says Israetel when discussing hypertrophy.
For strength, however, he says, ‘Twice weekly training for strength beats once weekly training. Why? Because your nervous system gets more practice, literally more practice doing the lifts and getting better at them.’
In practice, spreading your weekly training volume across multiple sessions can help manage fatigue, while practising specific lifts more frequently may help improve maximal strength.
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5. Lift Heavy and Early to Build Strength
The review found that loads of at least 80% 1RM were more effective for improving maximal strength. Exercise order also mattered, with movements performed earlier in a session generally producing better strength improvements.
‘Training over 80% one rep max is notably better for strength than training under 80% one rep max,’ explains Israetel.
He recommends performing much of your heavy strength work between 80% and 90% 1RM, typically for sets of 3-6 reps.
‘Earlier exercises in a session get the best strength gains compared to later exercises in a session,’ he adds.
If increasing your deadlift is the goal, for example, it makes more sense to perform it before accessory exercises rather than after several demanding sets.
6. You Don’t Need Endless Heavy Sets to Get Stronger
The review identified 2-3 sets per session as an effective prescription for strength development.
Israetel says, ‘As few as two heavy sets per session can boost strength meaningfully in very many people.’
He suggests performing between 2-5 heavy sets per exercise, depending on experience, recovery and training goals.
Rather than filling a workout with heavy compound movements, prioritise a small number of important lifts and use the remainder of the session for accessory or hypertrophy work.
7. Train Explosively to Develop Power
For power development, the review found that moderate loads of 30-70% 1RM, low-to-moderate volumes and lifting with an intentionally fast concentric phase were beneficial.
‘Every time you are training for power effectively, you want to push or pull the bar as hard as you can on each concentric of every single rep,’ says Israetel.
Unlike hypertrophy, where higher volumes can produce greater growth, power training benefits from keeping fatigue relatively low.
‘Low to moderate volumes are better than high volumes. Sessions of 2-5 sets of 2-5 reps per set are going to be how you gain the most power,’ he explains.
Whether you’re performing jump squats or Olympic lifting variations, the emphasis should be on explosive movement while maintaining control and technique.
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