Should women lift light weights?

May 21, 2012 at 4:31 p.m. ET

Bench-pressing heavy weights is a challenge, even with a spotter, but new research shows that consistent workouts with light weights is just as effective at building muscle. The more muscle we have, the more revved our metabolism gets, even while resting. So, ladies, no more worries about trying to keep pace with the guys at the gym!

Woman lifting weights

Lifting less weight more times is just as effective at building muscle as training with heavy weights, researchers at McMaster University in Hamilton, Ontario, say. New findings turns conventional wisdom on its head.

The key to muscle gain is working to the point of fatigue

"We found that loads that were quite heavy and comparatively light were equally effective at inducing muscle growth and promoting strength,” says Cam Mitchell, one of the lead authors of the study and a Ph.D. candidate in the kinesiology department.

The research, to be published in the Journal of Applied Physiology, challenges the widely accepted dogma that training with heavy weights that can be lifted only six to 12 times before fatigue is the best avenue to muscle growth.

Less intimidating way to train muscles

"Many older adults have joint problems that prevent them training with heavy loads,” Mitchell says. "This study shows that they have the option of training with lighter and less intimidating loads and can still receive the benefits.”

For the study, a series of experiments were conducted on nine healthy male volunteers, ages 19 to 26, to measure how their leg muscles reacted to different forms of resistance training over 10 weeks.

The researchers first determined the maximum weight each subject could lift one time in a knee extension. Each subject was assigned to a different training program for each leg.

To see results, work muscles to fatigue

In all, three different programs were used in combinations that required the volunteers to complete sets of as many repetitions as possible with their assigned loads – typically eight to 12 times per set at the heaviest weights and 25 to 30 times at the lowest weights.

The three programs used in the combinations were one set at 80 percent of the maximum load, three sets at 80 percent of the maximum and three sets at 30 percent of the maximum.

Three sets with light weights just as effective as heavy weights

After 10 weeks of training three times per week, the heavy and light groups that lifted three sets saw significant gains in muscle volume, as measured by magnetic resonance imaging, which takes a photo of the muscle internally, with no difference among the groups. Still, the group that used heavier weights for three sets developed a bit more strength.

The group that trained for a single set showed approximately half the increase in muscle size seen in both the heavy and light groups.

Pump up the volume and consistency, not the weight itself

"The complexity of current resistance training guidelines may deter some people from resistance training and therefore from receiving the associated health benefits,” says Stuart Phillips, a kinesiology professor and supervisor of the study. "Our study provides evidence for a simpler paradigm, where a much broader range of loads, including quite light loads, can induce muscle growth, provided it is lifted to the point where it is difficult to maintain good form.”

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