We have piles of research showing a clear relationship between volume—the total number of sets you do for any given muscle group—and hypertrophy.

competing. Every body has a tolerance threshold, beyond which it begins to break down.

A 2017 study by Morán-Navarro and colleagues showed that pushing sets to failure causes more fatigue, which seems obvious if you’ve ever done it.11 Less obvious are the consequences of training to that level of fatigue. In this study, the researchers looked at creatine kinase, an enzyme often used as a proxy for muscle damage. Creatine kinase

If you’re going to push each set as hard as possible, you simply can’t do as many sets. And if you’re going to push each set less hard, you need to do more sets to compensate. I believe this is the correct way to think about it.

In research, a 2021 review showed that lifters can achieve statistically similar increases in muscle size regardless of whether they train to failure or merely close to failure.8 A litany of other studies shows the same thing.9 You need to train hard. You need to be close to failure. But reaching failure isn’t always necessary.

I just want you to be aware that your lifting velocity will decline as your muscles fatigue. If your reps aren’t getting slower, you’re most likely not close to failure, no matter how you define it.

Some coaches, especially in powerlifting circles, now use high-tech rep-speed trackers to measure changes throughout a set. That gives the coach an objective way to measure how close a lifter is to failure and use that data to decide how hard they should push for the rest of the workout.

Mechanical tension. Almost all muscle growth results from your muscles straining against resistance.

As long as you’re generally prioritizing heavier compound lifts by putting them closer to the beginning of your session, being flexible with exercise order is perfectly fine.