It’s time to lighten up—when it comes to weight training, that is. That’s what a recent study concluded when McMaster University researchers found that light weights are just as good as heavy weights for toning muscles and building strength.
For the past 20 years or so, professional organizations such as the American College of Sports Medicine and the National Strength and Conditioning Association have recommended training with heavy weights—ones you’re only able to lift eight to 12 times before your muscles give out. But this latest study found that pushing to exhaustion—no matter how much weight you press—is the real secret to stronger, firmer muscles.
In a series of experiments, a group of young men were tested to see how much weight they could lift doing a single knee extension, which works the quadriceps—the meaty muscle in the front of the thigh. After establishing their maximum weights, the men did a three-day-a-week program where they lifted 80 percent of their maximum for one set of eight to 12 reps; 80 percent of their maximum for three sets of eight to 12 reps; or 30 percent of their maximum for three sets of 25 to 30 reps. Surprisingly, at the end of 10 weeks, both the heavy and light weight lifters who went to three sets gained an equal amount of muscle mass, about twice as much as the group who only pumped iron for one set. Of those who lifted three sets, the heavy lifters did increased their strength more than the lighter lifters—but only by slightly more.
“The type of fatigue you get when you go out to 25 to 30 reps is what I call the sewing machine fatigue—your muscles get a little jiggly,” explains Stuart Phillips, Ph.D., one of the study’s principal investigators. “It’s a different type of fatigue than you get when you go heavy, but it’s fatigue nonetheless.”
Dr. Phillips says the fact that lighter weights get good results is terrific news for exercisers, especially for women who might skip the weight room for fear of bulking up and seniors who avoid weights because they’re concerned about joint pain or getting injured. “Now they can use less weight knowing they can still meet their goals,” he says.
That said, you don’t want to take the concept too far by using weight so light that you can lift them hundreds of times. According to Phillips, that’s probably a waste of time, akin to lifting a pencil over and over again. If you’re looking to stay in shape, it’s okay to swap your usual 10-pound dumbbells for a lighter weight with more reps.
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