The biggest mistake you make at the gym might be less about the weights you lift and more about how much downtime you take between sets, according to a new study from the University of Birmingham in the United Kingdom. (Psst...Here's Why Every Woman Should Lift Weights.)
Researchers looked at a small group of men to see how the time in between strength-training sets boosts or impairs muscle growth. The men rested either one minute or five minutes between each set. Then, researchers took biopsies to analyze their muscles. Turns out, those who rested longer built more muscle than the group who skimped on their rest between sets.
Although the study was conducted in a small group of men, the researchers say these results would apply to women as well since women build muscle at the same relative rate. And according to Leigh Breen, Ph.D., lead author on the study, these findings aren't just about bulking up, they apply to building lean muscle mass too.
The men in the study lifted moderate to heavy weights (think 60 percent of your max and higher), but Breen thinks that longer rest periods would be beneficial for anything 30 percent of your maximum capability and above. So if you can manage to do a couple curls with a 50-pound kettlebell, these results would apply when you're lifting anything 15 pounds and above.
Note: This doesn't quite apply to the one pound weights in your barre class, or even HIIT style lifting, which is as much about torching fat as it is about building muscle. Waiting so long between sets sort of defeats the purpose if that's your goal.
The bottom line? If you want to build strength and boost muscle tone, extend your rest periods and make sure your weights hit or exceed that 30 percent mark. If waiting a full five minutes between every set seems a little unfathomable (who has that kind of time?!) the researchers recommend starting out with 2-3 minute break periods when you're in the weight room.