How to Choose the Right Amount of Exercise to Improve Muscle and Strength

Does the bro science rep range check out?

If the clock is your primary guide to determining your exercise dose then you are likely over or under-training.

There is nothing special about an hour.

Granted, I am a huge proponent of the physical activity guidelines, and they use time thresholds for exercise: 150 minutes of moderate or 75 minutes of intense aerobic physical activity a week. The recommendation of two strength training sessions per week lack doesn’t have a time marker.

These recommendations are baselines for health and wellness, not universal markers for all potential fitness goals.

If you want to run a marathon, 150 minutes a week won’t cut it. On the flip side, if you use high-intensity interval training, you can improve your cardiac capacity with three weekly 4-minute Tabata sessions. Keep in mind a Tabata workout is not any exercise for 20 seconds on and 10 seconds off. It is a brutal max effort protocol on a cycle ergometer.

There isn’t a one-size-fits-all approach to optimizing training. We can provide universal recommendations for baseline fitness, but even that likely needs some adjustment considering training history, age, and current health status.

The lack of universal thresholds doesn’t mean you should just wing it in the gym. Trial and error is a useful but time-consuming tool. You can’t go back in time to compare strategies and see which is best (a primary reason why anecdotes are low-level evidence and are not as valuable as controlled research).

Fortunately, we have a lot of research that provides details and strategies for personalizing exercise to better predict the right dose.

The following studies provide a more objective approach to measuring training volume for the goals of building muscle and strength. I have successfully implemented these strategies into training programs for my patients, clients, and personal training.

Measure Total Sets, Not Time

If you are using standard resistance training for strength and hypertrophy, with traditional rep schemes and rest breaks, is time the best measure of volume?

First, what are the traditional measures?

To induce muscle growth (knowns as hypertrophy), muscles need to be pushed beyond their current capacity. This overload is accomplished by progressively increasing the total mechanical tension. We can lift more weight or lift the same weight more times to accomplish this goal.

If you read through lifting programs, you will often see the term ‘volume load,’ which is the reps x sets x weight. This number should progressively increase. The manner of increase varies by program type, a discussion for another day. For now, know that programming type (linear, undulating, blocked) likely doesn’t matter for hypertrophy.

How much volume should you aim for?

It largely depends on your training history. If you are new to the gym, I’d recommend a few sets of exercises per muscle group per week. As your body accommodates and delayed onset muscle soreness diminishes, you will need to ramp up quickly.

Rapid strength gains are common when you start exercising as your nervous system becomes more efficient. We recruit more motor units (connection points between the nerve and muscle), and they are better synchronized. Imagine 6 people trying to lift a large sectional. If they all lift at slightly different times, the task will be more challenging than if they all lift at once and sustain similar efforts. Adding two more people will make the task even easier. That’s roughly how the nervous system adapts to exercise.

Once you are past the beginner stage, research provides more guidance on how much exercise to perform. A recent systematic review concluded 12–20 sets per muscle group per week is likely the best range for most people. If you are a professional bodybuilder, you will likely exceed 20. If you are new to training, 12 may be too much. Some trial and error will be involved.

A quick caveat, 12–20 sets of any exercise intensity will be insufficient. The lifts need to stimulate hypertrophy by inducing overload. In other words, the reps matter, too.

So, how many reps should you perform per set?

The Repetition Continuum Needs an Update

If I asked you how many reps you should perform per set to build muscle, what would you say? If you have a history of lifting weights, have read blogs on training, or have spoken with people who train often, the range of 8–12 likely popped into your head.

That is the traditional repetition continuum. The graphic below is similar to the graphics you will find in most exercise physiology and strength and conditioning textbooks.

A 2021 review paper challenges this continuum.

The lead author, Brad Schoenfeld, is one of the leading researchers in the field of exercise physiology. In this paper, his team reviews the current body of evidence to determine if 8–12 is the best range for building muscle.

Turns out, there is nothing special about 8–12 reps

The original studies comparing different rep ranges showed greater anabolic hormone increases in participants who exercised in the 8–12 range, leading authors to conclude that range must be optimal. This is a classic example of mechanism vs. outcome.

Anabolic hormones assist with stimulating and supporting muscle growth (the mechanism), but the adaptations did not result in greater amounts of muscle growth (the outcome).

Despite the plethora of studies that have demonstrated equal muscle growth for low (<8), moderate (8–15), and high repetition (>15) ranges, the ‘hypertrophy’ range has remained ingrained in gym culture. There is nothing wrong with 8–12 reps per set. It is an effective strategy for building muscle, but there are two key considerations.

First, there is nothing magical about that range. You are not guaranteed muscle growth by lifting in that range. You need to perform enough sets (as mentioned earlier), and you need to lift at the right intensity.

For hypertrophy, your lifts should be close to failure. If you are stopping at 8 repetitions, your max out should be 10–11 reps. If you could crank out 20 but stop at 8, the load is too light. The rep range isn’t as important as the intensity and the number of sets.

If you love the burn that comes from lifting, choose higher rep ranges (>15). If not, aim for lower ranges (4–8). Heavy singles and doubles are inferior for muscle growth, will fatigue you more, and likely increase muscle soreness.

If you are over the age of 59, you may respond better to light load training.

Although, as you age, the weight-bearing activity becomes more important as bone mineral density requires it.

What About Strength?

The image above summarizes all of the findings of the Schoenfeld article.

The authors suggest a minimum threshold of 30% of 1-rep-max is needed for optimal levels of hypertrophy. If your bench press is 200 pounds, the weight shouldn’t drop below 60 for developing muscle. Even if you go to failure, 50 reps are likely inferior to 20. The new rep range is likely around 4–30 instead of 8–12.

If you want to maximize hypertrophy, you must take into account diet, sleep, and stress. If you don’t recover well, your performance will suffer, limiting the amount of overload you apply to the muscles. Spreading out your training over more sessions may help as well.

Some research suggests frequency may be a key to hypertrophy. Each muscle group should be trained at least twice a week. Spreading out the sessions, as opposed to massing 15 sets of biceps once a week, should help with recovery.

Building muscle is hard work.

Instead of worrying about the ideal rep range, focus on training close to failure, progressively increase your volume, and ensure your recovery is on point.

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