A common belief about working out might be bogus -- and it's good news for anyone trying to tone up

Whether you want to tone up, slim down, or give yourself a mood boost, you’ve likely taken a stab at mixing some kind of weight training into your routine.

There’s a common conception that the best way to build muscle quickly is to do fewer repetitions, or complete cycles of the exercise, with heavier weights. For example, you might be encouraged to do 5 reps of arm curls with 15-pound weights instead of doing 12 reps of the same exercise with 8-pound weights.

A new small study published this month in the Journal of Applied Physiology (based only on men, unfortunately) suggests that’s not true. Instead, the paper suggests that lifting lighter weights for more repetitions is just as good as lifting heavier ones for fewer reps. That’s good news for those of us who might have been turned off by the idea of having to pump hefty loads that could end up injuring us.

The new study looked at 49 young men who’d been weight training for at least a year. For about three months, half of them did the standard heavy-weight, fewer-rep plan. The other half did a lower-weight, more-reps plan. As part of the first group, the lifters used weights set to be between 75% and 90% of the highest weight each person could lift once. The men in this group were instructed to do 8-12 reps, or until they were completely worn out — something the researchers called “volitional failure.” The men in the second group, on the other hand, had their weights set at between 30% and 50% of the highest weight each person could lift once. They were told to lift 20-25 times, or until they were also worn out.

All of them did three sets of the exercises four times a week.

At the end, the researchers found no significant differences between the two lifting groups — they’d all built bigger, stronger muscles.

So if you’ve ever avoided the weight room because you’re turned off by the idea of pumping fistfuls of bulky iron, think again, and consider trying out a plan doing multiple reps with lighter weights.

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