Bodybuilders are usually failures, while powerlifters usually are not. Before you take offense at that statement, hear us out. What we mean is that most powerlifters do not routinely train to muscle failure. Bodybuilders, on the other hand, tend to focus all their training on muscle failure.

Who’s right? Who’s wrong? And if failure is the way to go — how much failure is enough, and how much is too little? Here’s the scoop on how to fail for success.

The Form Principle | How muscle failure is defined can vary from one person to the next. Extremists consider it to be the total inability to move a weight.

This is exemplified by either the guy in the gym who uses contorted body English to complete his reps until he literally can’t budge the bar (sometimes he gets pinned under it during a bench press gone horribly wrong) or the one whose spotter totally lifts the weight for him.

Don’t be either — in the first scenario, you risk injury and, in the second, you only piss off your spotter for no appreciable gain.

As a bodybuilder seeking muscle growth, the kind of failure you want to reach should be defined as the point at which you can no longer perform another complete rep with proper form. Going to failure this way will properly fatigue the muscle and not put you or your spotter at risk for injury. Sure, go ahead and finish that last rep with less than stellar form — but stop there.

One note: if you train solo, then failure has a different definition by necessity. For you, muscle failure is the point at which you know you won’t be able to complete the next rep with good form. If you can’t complete it with good form, there’s a chance you won’t be able to complete it at all.

If this happens during a barbell bench press, squat, leg press or shoulder press, it could leave you open to a serious injury. Stop the set there before you even attempt that rep, and consider it a set done to failure.

Strong Evidence | Most powerlifters don’t train to failure. They usually stick to a tight regimen of a certain number of reps per set and never do more than that prescribed for the day’s workout. If a set feels light and they can get more than five reps (or whatever that day’s workout calls for), they still stop at five and simply add weight during the next workout. Recent research, however, should have most powerlifters thinking about changing their training strategy.

For more on the results of the study and how to benefit from failure, pick up a copy of December FLEX, available now on a newsstand near you.