What’s the single best way to train in order to build muscle?

Ask this question to a room full of fitness experts, and your ears will soon be bleeding from the raucous response.

Listen closely, though, and you’ll notice that most of their answers can be bracketed into one of two camps:

1. You should train heavy (focus on intensity).
2. You should train a lot (focus on volume).

The “volume vs. intensity for hypertrophy” debate has been simmering for years, and zealots on both sides of the fence make compelling arguments.

Intensity proponents claim that using heavy weights for low reps produces more tension on your muscles, which is ultimately what makes them grow bigger and stronger.

Volume boosters contend that the total number of sets and reps you do is what drives muscle growth, not the weight on the bar.

Who’s right?

As you might imagine, the truth is somewhere in the middle. While one of the two is slightly more important than the other, neglecting either volume or intensity will handicap your gains.

First, let’s define what volume and intensity really are (the answer isn’t obvious).

## What Is Volume?

Volume refers to the total amount of work an athlete is doing over a period of time, and in weightlifting, it can be measured in several ways.

One popular method of calculating training volume is to multiply the weight used by the sets and reps performed on an exercise. This is referred to as volume load. For example, if you do 3 sets of 5 reps of squats with 315 pounds, your volume load would be 4,725 pounds (3 x 5 x 315).

This formula produces big, impressive numbers that can be fun to track, but changes in volume load don’t correlate well with muscle hypertrophy or strength gain.

In other words, volume load is what a business owner might call a “vanity metric,”—a stat that makes you feel good but doesn’t help you understand your own performance in a way that informs future decisions.

For example, let’s say you switch from 3 sets of 5 reps of squats with 315 pounds to 3 sets of 12 reps of squats with 185 pounds. This bumps up your volume load to 6,660 pounds—a 40 percent increase—but research shows that this isn’t likely to produce more muscle growth and will probably result in less strength gain.

The reason for this is that any weightlifting set taken close to failure in the range of 6-to-20 reps will produce about the same amount of muscle gain. That is, a set of 6 reps taken just shy of failure will produce similar results as a set of 20 reps taken just shy of failure.

That means wildly different volume loads can produce more or less the same amount of muscle gain, so how are you supposed to use those numbers to optimize muscle growth? You can’t.

Another way to track your training volume is total repetitions, but this is flawed for the same reason volume load is. Using the same example as earlier, 3 x 5 reps gives you 60 percent fewer reps than 3 x 12 reps, yet both of these workouts are likely to produce similar amounts of muscle growth. The same thing is true of tracking volume as sets x reps—the numbers simply don’t correlate with muscle hypertrophy.

So, what’s the best way to quantify volume for the purposes of workout programming? Most research shows that the answer is hard sets, which are sets taken within 1-to-3 reps of muscular failure.

There are a few caveats to this you’ll learn about in a moment, but as a general rule, tracking the number of hard sets you do is the best way to track weightlifting volume.

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## What Is Intensity?

Intensity refers to how hard an athlete is training, and in weightlifting, it can be measured in a number of ways.

One of the simplest and most useful ways to measure weightlifting intensity is a system known as Reps In Reserve (RIR), which is how many more reps you could have done in a set before failure.

Failure is the point at which you can’t complete another rep with good form, and you can think of it as the limit of your ability. Basically, it’s the maximum number of reps you could do with a particular weight if you had a gun to your head (or maybe a million dollars waiting for you, if lucre is more motivating than self preservation).

Once you estimate roughly how many reps it would take to reach failure with a particular weight, you can measure your weightlifting intensity in terms of how many reps you could have done, but didn’t. In other words, how many reps you had “in reserve” at the end of your set.

If you’re like most people, this is how you naturally talk about your weightlifting sets. After a set of hard squats, for instance, you might say, “Man, that was a grinder—I had maybe 1 rep left in the tank.”

To estimate your RIR for a particular set, ask yourself this question at the end of the set, just before re-racking the weight: “If I absolutely had to, how many more reps could I have gotten with good form?”

So, how can you use RIR to help you build muscle? By taking note of your RIR at the end of each set, you can ensure you’re using heavy enough weights to maximize muscle growth.

Scientists still debate how close you should train to failure to build muscle, but a good rule of thumb is that you should end most of your sets 1-to-3 reps shy of failure, or 1-to-3 RIR.

There are a few other ways to measure weightlifting intensity that are worth learning about:

Measuring your weightlifting intensity as a percentage of your one-rep max is a useful tool for periodizing your workouts, but it’s typically unnecessary for most people who are new to weightlifting.

Relative perceived exertion is simply how hard a workout feels on a scale of 1-to-10, and it tends to work best for measuring intensity in endurance or mixed sports (soccer, basketball, etc.). RIR is simply a better way of measuring RPE for weightlifting.

## Volume vs. Intensity: Which Is Better for Hypertrophy?

Neither—you need both!

Many people make the mistake of thinking that building muscle is all about how much you lift or all about how many sets and reps you can cram into your workouts, but both approaches are wrongheaded.

To understand why, you first need to understand what causes muscle growth in the first place.

“Muscle growth occurs due to cumulative tension stimulus over time,” explains Dr. Eric Helms, a researcher, natural bodybuilding coach, and member of Legion’s Scientific Advisory Board. In other words, you build muscle by contracting your muscles at a sufficient intensity for a sufficient duration over time. The process of increasing the amount of tension your muscles are exposed to over time is known as progressive overload

You can increase this “tension stimulus” over time in two ways:

1. Increase the amount of tension produced in each rep by lifting heavier weight.
2. Extend the amount of time your muscles are exposed to tension by doing more sets or reps.

With the first option, you use heavy weights for relatively few reps, forcing your muscles to contract very hard for a brief period of time. With the second option, you use lighter (though not necessarily “easy”) weights for more sets or reps, forcing your muscles to contract moderately hard for a longer period of time.

Thus, you wind up producing about the same total amount of tension with both approaches. This is why research shows that sets taken close to failure in the 6-to-20-rep range all produce about the same amount of muscle growth—they produce about the same amount of cumulative tension by the end of the set.

Here’s an example to help illustrate how this works in practice.

Imagine you bench press 225 pounds for 5 reps. The muscle fibers in your chest, shoulders, and triceps are redlining during all 5 reps, but the set only lasts about 15 seconds. Now imagine that you bench press 185 pounds for 10 reps. Although your muscle fibers don’t contract quite as hard on any individual rep, they do so for twice as long, producing about the same amount of total tension.

Thus, technically, volume is the primary driver of muscle growth, because it’s the volume of tension over time that makes your muscles bigger.

That said, this is predicated on a few important factors:

First, you’re taking your sets fairly close to failure (1-to-3 RIR is a good target). If you don’t push yourself hard enough in your sets, they won’t generate enough tension to appreciably stimulate muscle growth.

Second, you’re using sufficiently heavy weights. Research shows that untrained people need to use at least ~30% of their one-rep max to optimize muscle growth, and that people with more weightlifting experience may need to use even heavier weights (regardless of how many sets they do or how close they take them to failure).

Third, you’re doing sets in the 6-to-20-rep range. If you do more reps than this, you’ll likely have to use weights that are too light to stimulate sufficient tension in each set (see the previous point). If you do fewer reps than this, you’ll significantly reduce the amount of time your muscles are forced to produce tension, thus shortchanging your gains.

This last point is worth elaborating on in more detail.

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### The Problem with Too Much Intensity

Many people think that the more weight they can lift, the more muscle they’ll build, and end up training like powerlifters

This approach is alluring because the weight on the bar (or dumbbell) is an easy, tangible proxy for muscle gain. If I can just add another 10 pounds to my bench press, that means I’ll gain muscle for sure!

The problem with this line of thinking is that getting stronger isn’t what causes muscle growth—muscle growth actually causes strength gain, because “ . . . bigger muscles are stronger muscles,” explains Dr. Helms.

“Therefore, muscle growth should eventually result in strength going up,” he elaborates. “But don’t get so hung up on strength to the point that you think putting weight on the bar is the only thing that matters, or that doing so is what causes hypertrophy. It’s actually the other way around, increased strength is a sign that you are providing an adequate overload for hypertrophy. You not only have to apply a tension stimulus (performing at an adequate RPE) for muscles to grow, but also ensure you have provided enough of that tension (volume; number of sets).”

Basically, if your strength is going up—if you’re able to lift more weight at the same RIR, the same weight for more reps, or for the same reps with more reps in reserve (it feels easier), then this is a sign that you’ve provided adequate progressive overload (tension) to build muscle, but it’s not what really makes your muscles grow.

Thus, the three main reasons to add weight to the bar in your workouts are:

1. To ensure that you’re still taking your sets close enough to failure to maximize tension in each workout. In other words, to maintain the effectiveness of your sets for building muscle.
2. To improve your ability to move heavy loads, which allows you to rack up more tension more easily during your workouts.
3. To gauge how well your program is working. For example, if your strength hasn’t gone up for a while, it’s a sign that your program might not be providing enough tension (undertraining), might be providing too much (overreaching), or that you might not be recovering properly from your training.

### The Problem with Too Much Volume

At this point, you may be wondering, if more tension equals more muscle growth . . . and more sets equals more tension . . . and training with light weights and high reps allows you to get more sets . . . then why not just train with light weights and high reps?

In other words, why not train how most muscle magazines say you should—bombing and blasting each body part with as many reps as you can stomach?

The problem with this myopic focus on volume is that there’s also a qualitative aspect to tension.

If the weights you’re using are too light, they won’t produce enough tension to stimulate an appreciable amount of muscle growth even if you’re doing a lot of reps.

As an extreme example, a professional cyclist might do 30,000 pedal strokes (reps) during a long workout, which produces more total tension than any bodybuilding workout you could imagine. This still isn’t ideal for building big legs, though, because the degree of tension produced by each pedal stroke is too small to stimulate much muscle growth.

The same principle holds true for very high-rep weight training—it doesn’t “count” toward your tension total the same way heavier weightlifting does.

There are three other problems with really high-rep, low-intensity training:

First, it’s very time consuming. If you train with 40, 50, or even 60% of your one-rep max, you’re going to be doing about 35, 25, or 15 reps per set, which takes a long time. These sets also tend to cause a lot of cardiovascular fatigue (they make you out of breath), which takes longer to recover from.

Second, this kind of training tends to be very, very unpleasant. For example, a study published in the Journal of Strength and Conditioning Research found that although people doing 3 sets of 25-to-35 reps per set gained just as much muscle as people doing 3 sets of 8-to-12 reps, they rated their workouts as far more uncomfortable and often threw up while training.

Third, doing very high-rep sets on exercises like the squat, bench press, and deadlift can be dangerous, as your form often starts to drag anchor as you become more fatigued.

Thus, while volume is important, you also don’t want to do so much that you aren’t able to train with sufficiently heavy weights.

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## So . . . How Should I Train?

Where does all of this leave us?

The weight of the scientific evidence indicates these are good guidelines for balancing volume and intensity to build muscle:

• Do 10-to-20 sets per muscle group per week.
• Use 60-to-95% of your one-rep max (between 2-to-15 reps) for most of your sets.
• Take all sets 1-to-3 sets shy of failure (1-to-3 RIR).

In terms of how many of your sets should be devoted to lighter or heavier training, Dr. Helms recommends that you get about ⅔ to ¾ of your total sets in the 6-to-12-rep range and the remaining sets in the 1-to-6 and 12-to-15-rep ranges.

If you’re looking for a workout program based on these guidelines, check out the Bigger Leaner Stronger program for men and the Thinner Leaner Stronger program for women.