Should You Pre-Exhaust Your Muscles? An Answer According to Science

If you’ve spent any time in a commercial gym, you’ve probably heard about pre-exhaustion—an “advanced” training technique in the same vein as drop sets, forced reps, slow negatives, and the like.

The concept sounds intriguing, too.

You fatigue a muscle slightly with an exercise or two—pre-exhausting it—and then continue with your workout until your muscles are even more swollen, sore, and tired than they would have been if you’d started your workout fresh. Then, your muscles grow even bigger and stronger as a result. 

That’s the idea, anyway, but the reality has been less exciting.

Many studies have shown that it offers no benefits or even reduces strength and muscle gain, while several others have shown it may be worthwhile after all. 

So, who’s right? 

Are the pre-exhaustion bros onto something, or are the pre-exhaustion deboonkers correct?

To help cut through the confusion, scientists at Catholic University of Brasília conducted a study to puzzle out the merits or demerits of pre-exhausting your muscles before training. 

In this study, the researchers wanted to see what effects pre-exhaustion had on muscle growth, strength, and body composition, and whether it offered any benefits over regular strength training. 

Let’s take a look at what they did.

What Is Pre-Exhaustion?

Pre-exhaustion is a technique whereby you perform an isolation exercise (an exercise that involves a small number of muscles) immediately before performing a compound exercise (an exercise that trains a large number of muscles) that trains the same muscle group.

For example, you might do some cable flys, which emphasize the chest, immediately before bench pressing, which also trains the chest.

How is this supposed to help you get more jacked, exactly? 

Well, proponents of pre-exhaustion claim that a compound exercise like the bench press doesn’t effectively train all of the muscle groups involved. 

For instance, advocates of pre-exhaustion would say that because your triceps are smaller and weaker than your chest muscles, they’re going to give out sooner during a set of bench press. In order to make the exercise equally challenging for all of the muscle groups involved, you should “handicap” your chest by fatiguing it with a few sets of another exercise first.

This way, your triceps and chest muscles will fatigue at roughly the same rate during a set of bench press, equally stimulating both muscle groups. 

What Did the Researchers Do?

During the first three weeks of the study, the participants did a handful of workouts with the researchers to familiarize themselves with the leg press and leg extension exercises and to determine their one-rep maxes for both exercises. 

For the next nine weeks, the first two groups trained twice per week, doing three sets of leg presses to muscular failure with 75% of their one-rep max and resting one minute between sets. A pretty brutal workout, to be honest. 

To fatigue their quads, the pre-exhaustion group performed one set of leg extensions to muscular failure using 20% of their one-rep max immediately before their first set of leg press. 

After their sets of leg press, both groups performed one moderately-hard 10-to-12-rep set of several upper body exercises to round out their workout.

The researchers had all of the participants retest their one-rep maxes every two to three weeks, and used the result to increase their weights throughout the study. Before and after the study, the researchers also measured the participants’ lower-body muscle thickness using skinfold calipers and body composition using DXA, and assessed their dietary habits by having them complete a three-day food log.

What Were the Study Results?

Much to the chagrin of gym bros everywhere, the researchers found no significant differences between either of the training groups when it came to measures of muscle growth, strength, or body composition.

That is, the people using traditional training methods gained just as much muscle and strength as the people who pre-exhausted their muscles.  

There were only two semi-meaningful differences between the two groups:

1. The traditional training group did significantly more volume (measured as sets x reps x weight lifted) throughout the study than the pre-exhaustion group.
2. The pre-exhaustion group increased their leg extension one-rep max significantly more than the traditional training group.

Both of these results are easily explained, though.

First, the traditional training group was probably able to do more total volume because they were less fatigued before their sets. This is an important point, as it highlights one of the problems with pre-exhaustion: if you fatigue a muscle group before a workout, you probably won’t be able to do as much volume during that workout.

As doing more volume is one of the most effective ways to gain muscle and strength, it’s reasonable to assume that pre-exhausting your muscles might actually hamper strength and muscle gain over time. 

Second, the reason the pre-exhaustion group increased their leg extension one-rep max was probably because they were actually, you know, doing leg extensions, which the traditional training group was not. 

What Does This Mean for You?

After all, pre-exhaustion didn’t offer any benefits in terms of muscle growth, strength, or body composition compared to traditional training, and decreased how much volume the participants could do in their workouts. 

There’s another way to look at the results, though: 

You could also say the pre-exhaustion group got exactly the same results as the traditional training group while doing significantly less volume (especially during the last half of the study).

In other words, they did less work but reaped equal rewards.

The catch, of course, is that the pre-exhaustion group also had to gut out a set of leg extensions to failure before each of their workouts, but this allowed them to do fewer reps throughout the rest of their workout while making equal gains as the traditional training group. 

And while this isn’t exactly what pre-exhaustion is purported to do, it’s still an interesting side benefit.

Before we all climb aboard the pre-exhaustion bandwagon, though, there are plenty of questions left unresolved by this study.

For instance . . .

• Does pre-exhaustion only offer benefits when used with isolation exercises and when using machines (like the leg press), or would it have a similar effect with free-weight compound exercises (like the squat)?
• Would the effect have been more pronounced if the participants hadn’t taken their pre-exhaustion set to failure, or if they’d been allowed more rest between sets? (Other research suggests this is possible.)
• Would the results have been different if they’d used the same exercise for both the pre-exhaustion set and the working sets? (Again, a different study suggests they might.)
• Would the benefits hold true over the long-term or would the reduced volume hamper progress months and years later?

. . . and so on, and so forth.

Until we have answers to questions like these, it’s hard to call this a victory for the pre-exhaustion crowd.

So, where does this leave us?

All things considered, it’s probably sensible to stick with a more traditional style of training, at least for now. And if any muscles feel under-stimulated after a compound exercise, there’s no reason you can’t add in some supplementary isolation exercises at the end of your workout.

For example, if you feel your triceps aren’t being adequately trained by your bench pressing, you can always do some triceps extensions or close-grip bench press afterward.

The only other times you might think about including pre-exhaustion in your training is if you’re recovering from an injury and looking for a way to increase the intensity of an exercise without increasing the weight. Even in this case, pre-exhaustion is unlikely to offer much benefit, but it probably won’t hurt, either.

The Bottom Line on Pre-Exhaustion

Despite what pre-exhaustion tub-thumpers claim, a study conducted by scientists at Catholic University of Brasília found that pre-exhaustion training wasn’t any better than traditional weightlifting when it came to muscle growth, strength, and body composition.

One point of interest the researchers did uncover, though, was that despite doing significantly less total volume over the course of the study, the participants who used pre-exhaustion in their training got exactly the same results as the traditional training group.

A counterargument to this, though, is that pre-exhaustion also reduced how much volume the participants could do in their workouts, which could reduce muscle and strength gain over time. 

Thus, all in all, the main takeaway from this study is that it’s probably best to stick with traditional strength training and not get too distracted with training techniques like pre-exhaustion.

If you want to learn more about tried and true ways to build muscle, check out these articles:

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