Similar Muscle Growth From Training to Failure vs. Stopping a Few Reps Short

Key Points:

A new study had 18 resistance-trained participants train one-sided leg presses and leg extensions twice per week for eight weeks.
One of the legs trained to failure in each set, while the other leg stopped 1–2 reps short of failure.
Muscle growth was similar in both legs. Both failure training and keeping 1–2 reps in reserve (RIR) are viable strategies for muscle growth, but there are considerations for when one is more suitable.

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Do you build more muscle if you train close to failure?

Current research states that it doesn’t seem to matter much if you take your sets to failure or stop a few reps before; you’ll gain strength and build muscle equally fast with both methods.¹ ²

A meta-regression of 26 studies, however, found that taking sets closer to failure might positively influence muscle hypertrophy but not strength gains.³

A new study, published just a week ago, adds to the research as it investigated if training to failure vs. stopping one to two reps short impacted quadriceps muscle growth in participants with several years of resistance training experience.⁴

What They Did

The researchers recruited 18 participants (12 men, 6 women) between the ages of 20 and 38 years. The participants had an average of seven years of resistance training experience, and half of them had competed in either powerlifting or bodybuilding.

Each subject trained one leg to failure and the other to 1–2 reps in reserve (=stopping 1–2 reps before failure), using the one-legged leg press and leg extension. They did so twice per week, for eight weeks.

This is called a within-subjects design, and you might recognize it from my recent article on increasing weight vs. reps. It’s a great design choice for this study as it both “doubles” the number of participants, and reduces variability because of factors like genetics, diet, sleep, and training history.

One legged leg extension to failure — This study used the unilateral (one-sided) leg press and leg extension (pictured above). Every participant trained one leg to failure, and with the other leg stopped one to two reps before failure.

The training volume was individualized and based on the participants’ habitual quadriceps training volume before the study, and it fell between 10 and 14 sets per week. After week 4, the set volume was increased by 20%.

The set volume was split between the leg press and the leg extension, so if a participant previously performed 12 sets per week, they now did two workouts per week of:

Leg press: 3 sets
Leg extension: 3 sets

Leg Extension exercise — … and the leg extension. Although, in the study reviewed, the participants trained these exercises with one leg at a time.

For the reps in reserve-group, the leg press was trained with 2 RIR and the leg extension was trained with 1 RIR.

The workouts were supervised, and both legs were trained in each session. Every workout they alternated which leg (failure or non-failure leg) started the workout, as fatigue might affect the subsequent training.

Quadriceps muscle thickness was measured by ultrasound before and after the training period.

Great Growth, But No Difference

After eight weeks of training, both groups had increased their quadriceps thickness by 7% with no difference between groups.

Quadriceps muscle growth from training to failure or non-failure

This is an impressive rate of muscle growth considering the participants’ training experience.

My guess is that this effect can be chalked up to having a personal trainer encourage you to train hard during each of your workouts, and that a lot of people don’t train very hard when left on their own.

It did not make a difference, however, if the participants took their sets to failure or stopped one to two reps before.

One explanation for the similar muscle growth might be that the volume load (set x reps x load) didn’t differ between groups; on average, they performed the same number of reps and lifted the same amount of kilos.

When you train to failure, your number of reps per set typically drop off more than if you stop short of failure. So even if the failure-group did more reps in their first set each workout, the RIR-group caught up in the following sets.

While volume load is not the only thing that matters for muscle hypertrophy, it does seem to be one of the major determinants.⁵

So What Does This Mean For You?

Well, add this to the pile of studies showing that training all the way to failure doesn’t seem to offer any additional benefits over simply training close to failure.

And it’s not worse, either.

I’d guess that on a per-set basis, taking a set all the way to failure is probably a bit more stimulating for hypertrophy compared to stopping one or two reps short. But I think it incurs higher costs in terms of recovery time and performance drops in the rest of the session.

The authors conclude their article by listing a number of factors that might influence when to train to (or close to) failure, compared to training further from failure, which I think are sound:

When to Train Further From Failure

In the first exercises or sets within a training session.
In complex exercises with safety demands.
When doing high set volumes.
At the beginning of a training program.

When to Train Closer to, or to Failure

In the last set of an exercise or muscle group.
When using long rest periods between sets.
When doing low set volumes.
When you are well-accustomed to a training program.

You can also mix and match between the two methods.

Take our leg day workout for example: the workout begins with complex compound exercises like the barbell squat and Romanian deadlift – exercises in which you probably don’t want to push all the way to failure for safety or technique reasons. In these exercises, you could stop 1–2 reps shy of failure.

Then in the other half of the workout, when you’re doing simpler isolation exercises like the leg curl and leg extension, you can train to or closer to failure and squeeze the last bit out of your muscles.

Wrapping up, I want to point out that rarely do we gym-goers actually train to, or even close to, failure. In general, both beginners and experienced trainees tend to do too few reps with too light weights for optimal results.⁶

If you feel like you might belong in this camp (I am definitely guilty of this on several occasions), you might still want to try to push fairly close to failure, knowing that you’ll probably still end up finishing the set with a few reps to spare – the kind of reps that are hard to bring out unless you’ve got a gun to your head.

My point is that I don’t want you to read this article and think, “Oh, maybe I shouldn’t work as hard as I do in my sets”. Most of us should be working harder in the gym, and our results (or lack thereof) does not stand and fall with whether we had zero or one rep left in us at the end of the set; the important thing is that you didn’t have ten reps left.

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