How Close to Failure Should You Train to Build Muscle? (The Science Explained)

Three key training variables determine whether your workouts actually stimulate muscle growth:

• Mechanical tension and progressive overload

• Appropriate training volume

• Training close enough to muscular failure

Now there are other important things of course like fatigue management, resting long enough between sets, training at a long muscle length, etc but for the purpose of answering this question we will focus on these 3

Mechanical tension and progressive overload

In essence this means lift heavy and increase those loads over time.

How heavy? Well when building muscle is the focus anywhere between around 5-30 reps seems to produce similar muscle growth.

Image copied from @pheasyque

As always, there are important nuances to these numbers that we need to understand.

The first thing is exercise selection. I would not recommend doing 30 reps on your squats or deadlifts as in most cases your cardio will be your limiting factor. By this I mean, you will probably be out of breath and your form will be suffering before your muscles can even get close to failure.

In the same regard, I wouldn't recommend doing isolation exercises like bicep curls or lateral raises for 5 reps as the increased load required to reach failure by the 5th rep would be a lot for that single joint to handle, thus increasing the risk of injury. This means that the 5-30 guide requires a little bit of critical thinking. If I had to give a general rule of thumb though, I would say keep your compound lifts between 5 and 15 reps and your isolations at 8 reps all the way up to 30.

The second nuance to take into consideration is motor unit recruitment. Motor units are recruited based on how much force your muscles need to produce. When we train with heavy loads (close to our 1-rep max), the body quickly recruits higher-threshold motor units because a lot of force is required to move the weight.

When we train with lighter loads, these higher-threshold motor units are not recruited immediately. However, as the set continues and fatigue builds, the body gradually recruits more motor units in order to keep producing force.

This means that with lighter weights, we need to push closer to muscular failure in order to recruit those higher-threshold motor units that have the greatest potential for muscle growth.

Long story short: The higher the rep target we choose, the closer we generally need to push to failure.

Finally, don't rule out 1-5 rep range altogether. Research shows that the 1-6 rep range is better for increasing strength than the higher rep ranges. Now if you are reading this article you might think "I'm not too worried about strength, I just want to get bigger". But my friend, remember that one of the main mechanisms of hypertrophy is mechanical tension and progressive overload so if you want to get bigger, you should probably try to get stronger as well.

It's important to understand that pushing that close to your 1 rep max weight can bring extra fatigue and can increase your risk of injury so when you are trying to build strength I would recommend sticking within the 3-6 rep range mostly and only dipping below when you are testing maximal strength or working up to testing maximal strength.

Appropriate training volume

This is where I think many people get confused. They are told that more volume equals more muscle growth, and this is true. However training every muscle at a high volume all the time is generally a good way to either get injured or drive your fatigue way up and decrease performance. In terms of the correct number of sets, this is what research suggests

For beginners - 8-12 hard sets per muscle per week

For intermediate – 10-18 hard sets per muscle per week

For Advanced – 12-20 hard sets per muscle per week

And by hard sets I mean 5-30 reps taken close to failure

Example of the Reps in Reserve (RIR) scale used to estimate proximity to muscular failure during resistance training. Image copied from https://www.empower.physio/blog-all/rpe-vs-rir-1

Training close enough to muscular failure Muscular failure refers to the point where you can no longer complete another repetition with proper technique.

If you do not train close to failure in the rep ranges I have mentioned, you will not create enough stimulus to produce muscular hypertrophy. How close to failure? Most research suggest within around 3 reps potentially as far as 5 repetitions from failure.

Before you ask anymore questions let's get those nuances cleared up:

Nuance 1) Isolation movements can be pushed closer to failure than Compounds - Compound movements recruit more muscles - more muscles recruited generally means more weight can be moved - more weight moved and more muscles recruited generally means increased fatigue and increased risk of injury, especially when pushed to failure. As isolation movements usually only involve one muscle the weight that can moved is decreased so the fatigue and risk of injury when pushing closer to failure is decreased.

Nuance 2) Reps from failure can be hard to gauge - When you first start resistance training everything feels hard and like you are pushing close to failure. This was demonstrated in a study by Steele et al. (2017), where lifters were asked to predict how many repetitions they could perform before reaching momentary failure and then actually perform the set to failure. Beginners tended to substantially underestimate their capacity, sometimes completing around 4-7 additional repetitions beyond where they believed they would fail on some exercises.

In addition to this, the higher the rep target the harder it becomes to perceive how close you are to failure.

This is why it's important to push to failure now and again. When you do though I would use it sparingly and save it for the last set of the given exercise.

Conclusion The most important thing I want you to take out of this is to focus on pushing close to failure in a given volume first. If you see no growth in that rep range, then you can look at pushing up volume but only if you can say yes to the questions below first (1 no is okay).

1. Are you getting 7-9 hours of sleep per night?

2. Are you eating at maintenance or a surplus?

3. Are you consuming 1.6-2.2 grams of protein per kg of bodyweight?

4. Are your stress levels low?

5. Are you still enjoying your training (not dreading gym)?

If you answered yes, and you are not progressing you can look at increasing your volume by 1 set.

Remember though, increasing 1 set per muscle per week for all muscles can mean a lot of extra sets, more time spent in the gym and more fatigue so think of it from a muscle by muscle point of view. By this I mean, maybe you increase your chest volume by 1 set per week instead of every muscle in your body.

Key Takeaways

If you want to build muscle effectively:

• Train most sets within 1-3 reps of failure

• Perform roughly 8-20 hard sets per muscle per week

• Use a wide rep range (5-30 reps) depending on the exercise

• Progressively increase the load or reps over time

• Focus on quality hard sets first before increasing volume.