Reps in Reserve vs Training to Failure: Are You Training Hard Enough?

Should you train to failure if you want to make your muscles grow as fast as humanly possible? Or will you do just as well leaving a few reps in reserve?

The argument in favor of training to failure goes something like this…

If you want to build muscle as fast as humanly possible, you need to train to failure.

Stimulating gains in size and strength is an on-off phenomenon, much like turning on a light, and reaching momentary muscular failure is what it takes to flick the switch from off to on. 

Failure isn’t just the last rep you think you can do. It’s the point where your muscles throw in the towel and you literally fail to complete a full repetition.

A set should be terminated only when it’s physically impossible to move the weight any further.

If you stop short of failure, the growth mechanism hasn’t been triggered, and you’ve not given your muscles a clear reason to adapt and grow.

Does Training to Failure Work Better for Muscle Growth?

Most research shows that reaching failure is not a requirement for building bigger, stronger muscles. You’ll do just as well to leave some reps in the tank.

That is, it doesn’t matter if you hit muscle failure, or cut a set short knowing that you could have cranked out another rep or two. Your muscles will still grow at much the same rate.

That was the conclusion of a team of Brazilian scientists, who compared the effects of failure versus not-to-failure training on muscle growth [1]. 

One group of participants was instructed to lift to failure, while the other group stopped with a few reps in reserve.

After 12 weeks, ultrasound scans showed similar rates of muscle growth in both groups. 

Whether they trained to failure or not, gains were no different.

Research published in the Journal of Strength and Conditioning Research came to much the same conclusions [2].

Training to failure with heavy(ish) weights (80% of 1-rep max) had no adverse or beneficial effects on muscle growth compared with a similar volume of training that wasn’t performed to failure 

Training to failure didn’t help muscle growth. But it didn’t hurt either.

To quote the research team directly:

“When performing resistance training at high loads, muscle failure does not confer any additional strength or hypertrophy-related benefits compared with stopping well short of failure provided total training volume is equated between conditions.”

It was much the same story when researchers looked at how training to failure compares with cutting a set short with 1-2 reps in reserve  [3]. 

After 14 weeks of training, the average amount of muscle gained was not significantly different between the two protocols. 

So, what does all this mean for you and your workouts?

Building muscle takes a lot of hard work and effort, and you may end up failing on some of your work sets whether you planned to or not. 

However, doing so will give you no better gains than finishing each set feeling like you could grind out another rep or two. While muscle fatigue plays a role in stimulating growth, it’s not necessary to take a set to failure in order to create that fatigue.

Reps in Reserve

On the flip side, the popularization of concepts like reps in reserve and RPE has left many people worried that hitting failure is going to sabotage their results.

While failure isn’t something you need to chase, it’s not something to be feared either. 

In fact, there’s nothing uniquely beneficial or harmful about reaching the point in a set where you’re no longer able to lift a weight.

All that’s happened is that the amount of force produced by the various muscles involved in moving the bar from point A to point B – not all of which are fatigued to the same extent – is no longer sufficient to move the bar past a certain point. 

In the bench press, for example, failure is the point when, after lowering the bar to your chest, you can’t push it back to the starting position.

While your chest, triceps and shoulders are experiencing high levels of fatigue, they haven’t really failed in the sense that they’re still capable of doing more work.

Once you hit the point where you’re unable to lift the bar, you’ll still be able to lower it under control. And when you’re unable to lower it under control, you’ll still be able to hold it in place, if only very briefly.

It’s only when you’re not able to support the weight that you can say you’ve pushed a muscle to its “true” limit, or at least the limits available consciously. 

You also need to consider the issue of safety. Towards the latter stages of a set, the build-up of fatigue can easily lead to a breakdown in technique. 

During the last few reps of a squat, for example, when your lungs are locked in a desperate struggle for oxygen, and it feels like someone has taken a blowtorch to your quads, maintaining proper form can be extremely difficult.

It’s not so much of a problem with exercises like the leg extension or dumbbell curl, which don’t require a great deal of skill to perform. But training to failure on big compound lifts like the squat and deadlift, where technique is paramount, isn’t a great idea. 

Your form can start to break down before you hit failure, increasing the risk of injury.

Other than a drop in speed, your last rep should look much the same as the first. Don’t allow a set to go beyond the point where your form goes down the pan. Far better to leave a few reps in the tank than end up with an injury that keeps you out of action for months.

Final Thoughts

When you fail during a set, it’s a sign that you’re pushing yourself hard and generating a large amount of muscle fatigue.

Stimulating growth does require that you reach a certain threshold of effort, and pushing yourself to the limit is one sign that you’ve crossed that threshold. 

However, if you could take a look inside your muscles at the point where you hit failure, you wouldn’t spot any growth mechanisms being triggered, or muscle-building switches being flicked.

There’s very little evidence to suggest that intentionally training to failure needs to be the focus of your workouts, or that doing so is necessary for building bigger, stronger muscles.