Looking to get stronger? The amount of weight you lift makes all the difference, a new study from the University of Nebraska-Lincoln suggests.
Researchers had 26 men aged 19 to 35 lift to failure using a leg extension machine 3 times a week for 6 weeks. They were split into two groups, so half of the guys loaded the machine with 30 percent of their one rep max (1RM), while the other half lifted 80 percent of their 1RM.
They researchers tested for muscle thickness and strength when the men first started training, as well as during the third week and after they completed the 6-week routine. (Here's why every man should be lifting weights.)
After 6 weeks of training, they found that both groups saw similar growth in muscle size—but the high-load group saw a larger increase in their muscle strength. In fact, the guys that did heavier lifting increased their 1RM strength by about 15 pounds more than those who lifted lighter.
And the increase in strength may be due to a surprising cause: Lifting heavy may actually help you better activate the cells that transmit electrical signals to your muscles and the muscle fibers those cells supply nerves to, says lead study author Nathaniel Jenkins, Ph.D., C.S.C.S.*D. Scientists refer to those as your “motor units.”
That’s what the researchers discovered during a second part of their experiment, when they measured the kicking force of both groups of men while they received an electrical current to to stimulate their quads and when they kicked voluntarily on their own. With the application of an electrical current, you're typically able to produce more force than you would on your own—similar to what you’d be able to do if you were more fully activating your motor units.
They discovered that the guys in the high-load training group were able to produce more force when they kicked on their own than those who trained with lower load. This suggests that higher-load training may help you better activate your muscles. And that’s important for strength, since it can help your muscles produce more force. Meaning, it can make you lift more.
Now, this doesn’t mean you have to completely write off low-load lifting, especially because the low-load group still saw an increase in their strength, even though it wasn’t to the same extent as the guys who lifted heavier. But if you’re deloading, dealing with an injury, want to avoid putting a lot of stress on your joints, or just want to make your muscles grow, low-load training can still be useful, says Jenkins.
(No gym? No problem: Blast fat and build serious muscle with Metashred Extreme from Men’s Health—a series of high-intensity metabolic workouts you can do right in your own living room.)
The right training program should be individualized to your personal progress and goals, he says. But if you are focused on getting stronger, lifting heavy will ultimately be more efficient. In this particular study, high-load training was defined as 80 percent of your 1RM. Whether or not lifting slightly lighter loads would produce the same strength-building effects is yet to be determined, since more research needs to be done to find out, says Jenkins.
“Over the long term, training with high loads will help you spend less time in the gym,” Jenkins says. “You see greater strength adaptation accompanied by neural adaptation. That’s going to allow you to use heavier weights and increase your volume, which should allow for more rapid progression.”
