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Back in 2010, researchers at McMaster University proposed a heretical idea.

To build big muscles, they suggested, you don’t necessarily have to lift big weights. Instead, their research showed the same benefits from lifting light weights or heavy weights or pretty much any weight you want—as long as you lift to the point of failure, when you’re incapable of completing another rep.

The simplicity of this prescription is a welcome counterpoint to the usual complexity of strength training guidelines. It’s easy on the joints, simple to apply with minimal equipment and works as well at home or at the park as it does at the gym.

But pushing all the way to failure is a daunting prospect for all but the most hardcore lifters, and researchers have been split on whether it’s really necessary. The good news: a new review published last month suggests that, for most of us, failure is unnecessary and perhaps even counterproductive.

The original idea of training to failure was based on the way our brains recruit muscle, explains McMaster kinesiologist Stuart Phillips. When you lift a light weight, you can get away with activating only smaller bundles of muscle fibres. But as those fibres fatigue, you recruit larger and larger bundles until, at the point of failure, you’re recruiting everything you’ve got – just as you would if you’d started with a heavier weight.

That’s why Phillips and his colleagues had their subjects lift to failure when they first compared light to heavy weights. In practice, though, they didn’t think that pushing all the way to failure was necessary for everyone.

“In reality, with trainees in the gym and especially our older folks, we say work to 8 out of 10 on a perceived effort scale, and you’ll get 90 per cent of the job done,” he says. “Those last 10 per cent are the reps that tempt injury, and that really need a spotter.”

In fact, some researchers and strength coaches argue that lifting to failure leaves you so tired that you can’t do as many sets and need more time to recover afterwards, resulting in slower progress.

Over the years, 15 different studies with a total of nearly 400 subjects have compared lifting to failure with stopping short of failure. The results of these studies are aggregated in the new meta-analysis, which was led by Jozo Grgic of Victoria University in Australia and Brad Schoenfeld of Lehman College in New York and published in the Journal of Sport and Health Science.

Overall, they found no significant difference in strength and muscle growth between the two approaches. Studies with experienced lifters did show a slight edge in muscle growth when lifting to failure, but the main takeaway is that failure is optional.

That leaves an unanswered question, though. How close to failure do you need to go?

In a study published last year by Cleiton Libardi of the Federal University of São Carlos in Brazil, adults in their 60s and 70s spent 12 weeks lifting either all the way to failure, just short of failure or on a fixed program of three sets of 10 reps, all with a relatively light load equal to 40 per cent of the heaviest weight they could lift.

The latter group did less than a third as much total training as the failure group. And yet, surprisingly, all three groups improved their strength by similar amounts (21 to 23 per cent), and saw similar improvements in functional tests such as walking speed and getting up from a chair.

For competitive athletes and bodybuilders and others looking to squeeze every drop from their strength workouts, the debates will continue about the most effective weight and number of reps and so on. Lifting close to failure is probably optimal, Libardi says.

But for the rest of us, the picture that emerges from these studies is more forgiving, says James Steele, a researcher at Solent University in Britain who studies resistance training.

“I think just ensuring that a reasonably high degree of effort is employed, and that training is a consistent and long-term behaviour, are the most important factors,” he says.

Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Twitter @sweatscience.

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