One study that caught my eye this week, from John Sampson and Herbert Groeller at the University of Wollongong in Australia, looked at failure versus not-to-failure training and its effect on gains in size and strength.
Sampson and Groeller took a group of 28 untrained men and assigned them to one of three groups.
All three groups followed the same training program for 12 weeks. This involved four sets of arm curls, separated by three minutes of rest, performed three times a week.
The only difference was that one of the groups took every set to muscular failure – that point where you’re unable to complete another rep using correct technique. Groups two and three stopped each set before reaching failure.
Subjects in the failure group averaged six reps per set. They also used a controlled rep tempo, taking two seconds to lift the weight, and two seconds to lower it.
Group two, on the other hand, left 1-2 reps in the tank at the end of each set. They also used a slightly faster lifting speed, raising the weight as quickly as they could, and taking around two seconds to lower it.
Subjects in the third group also stopped a couple of reps short of failure, but they lifted and lowered the weight as quickly as possible.
At the end of the study, all three groups had gained size and strength. But the researchers could find no significant differences between them.
Despite a substantial decrease in training volume, participants in the two not-to-failure groups gained just as much size and strength as the ones who took every set to failure.
One major limitation with this study is that it looked at a group of untrained beginners training their elbow flexors (the biceps and brachialis). It doesn’t tell us how trained individuals, or indeed other muscles, would respond to the same program.
What’s more, the fact there were no statistically significant differences in muscle growth doesn’t mean there were no differences at all.
The failure group made the greatest gains, posting an 11.6% increase in muscle size. This compares to a 10.9% gain in the slow not-to-failure group, and a 7.1% gain in the fast not-to-failure group.
In addition, both not-to-failure groups performed a single set to failure each week. This allowed the researchers to adjust the amount of weight that was used the following week. Although just one of the 12 weekly sets was taken to failure, this could have had an impact on the results.
One interesting feature of this study, which I haven’t seen tried before, is the way that Sampson and Groeller tried to ensure that all three groups contained an equal number of low and high responders.
We know that some people gain size and strength faster than others, even when following the same training program. We call them high or fast responders. Other people progress more slowly, and are referred to as slow or low responders.
If by chance, a large number of fast responders had ended up in one of the three groups, it could have skewed the results.
To separate the high and low responders, a four-week familiarization phase was inserted at the start of the study. The people who made the slowest strength gains during this phase were classed as low responders, while those who gained strength the fastest were labeled high responders. Sampson and Groeller then made sure that an equal number of high and low responders were assigned to each of the three groups.
This is a nice idea, in theory at least. However, I’m not convinced that strength gains in the elbow flexors after four weeks of training is sufficient to distinguish between high and low responders.
Other studies on the subject have separated the two by looking at gains in muscle mass over a longer period of time. One trial, for example, found roughly four times greater gains in muscle mass in the high versus low responders over a 12-week period .
Muscular failure is usually defined as the point at which you’re unable to complete another repetition using correct technique.
But not-to-failure, on other hand, might mean stopping a set 1-2 reps short of failure. It could involve taking a long pause between each rep, or inserting a 30-second rest period in the middle of a set.
In other words, not-to-failure is a term that can mean different things depending on which study you look at, and may involve terminating a set relatively close to, or some distance from, momentary muscular failure. That’s one of the reasons why studies that compare failure with not-to-failure training often throw up conflicting results.
Building muscle takes a lot of hard work and effort, and chances are that you’re going to end up failing on some of your work sets whether you planned to or not. But there’s very little evidence to suggest that it needs to be the focus of your training, or that intentionally training to failure is necessary for building bigger, stronger muscles.
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ABOUT THE AUTHORChristian Finn is a former "trainer to the trainers" and fitness writer based in Northamptonshire, England. He holds a masters degree in exercise science, and has been featured in or contributed to major media on two continents, including the BBC and Sunday Times in the U.K. and Men’s Health and Men’s Fitness in the U.S.
1. Sampson JA, Groeller H. (2016). Is repetition failure critical for the development of muscle hypertrophy and strength? Scandinavian Journal of Medicine and Science in Sports, 26, 375-383
2. Davidsen PK, Gallagher IJ, Hartman JW, Tarnopolsky MA, Dela F, Helge JW, Timmons JA, Phillips SM. (2011). High responders to resistance exercise training demonstrate differential regulation of skeletal muscle microRNA expression. Journal of Applied Physiology, 110, 309-317