Lifting Lighter Weights Still Causes Muscle Growth

Heavy weight training isn’t the only way to get stronger.

By: Melissa Romero

Personal trainers often hear their female clients say, "Don't make me bulky!"

But any fitness expert can tell you it takes a lot more than lifting five-pound weights to get you body-builder-esque muscles. However, for those who aren't scared to tone up and get stronger but still can't bench press 200 pounds, there's hope: Lifting less weight more times is just as effective at building muscle as using heavy weights, according to a new study published in the Journal of Applied Physiology.

The key to muscle growth, researchers said, is not how heavy a weight you use. Rather it's working until you can't go any longer, otherwise known as the point of fatigue or failure.

The study involved 18 young, healthy men who were assigned to three different leg-strengthening programs for ten weeks. One program involved performing one set of knee extensions at 80 percent maximum load. The second involved three sets at 80 percent maximum load, and the third included three sets at 30 percent maximum load. For heavy sets, the men lifted 8 to 12 times, and for lower-weight sets they lifted 25 to 30 times.

At the end of the study, researchers found that the volunteers in the heavy and light groups who lifted three sets had equally significant gains in muscle growth. The group that performed one set gained only half as much muscle.

Trainer Lance Breger, who wasn't involved with the study, said the results could be due in part to the high-volume training program. "The more volume or total workload, the bigger muscles may become," he said. "Also with higher reps, a muscle will be under tension for longer periods of time, going through more contractions," thus causing more muscle growth.

While the researchers noted that the three-set, heavy-weight group ended up being a bit stronger than the light-weight group, the results are still promising, especially for older adults. "Many older adults can have joint problems, which would prevent them training with heavy loads," lead researcher Cam Mitchell said in a statement. "The study shows that they have the option of training with lighter and less intimidating loads and can still receive the benefits."

The results are sure to challenge trainers' current weight-lifting routines for clients: "If this study is true, trainers are doomed!" Breger says. "We'll have to count correctly over 12 and be bored to tears watching Jane Exerciser doing 30 bicep curls."

The full study is available at the Journal of Applied Physiology website.