Science has tested exactly what it takes to tone up, so you don't have to.
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Getting ultimate gains doesn’t need to be a guessing game. Science has your back… and your shoulders… and your biceps.

According to researchers at McMaster University, the best way to build muscle may come in many different forms. Their study, published in the Journal of Applied Physiology, found that lifting heavy or light weights are both equally effective at bulking you up.

For the study, about 50 experienced male lifters participated in a 12-week resistance training program. They did the same workouts each day, including barbell bench presses, biceps curls, leg presses, and knee extensions, among other exercises. While half of the subjects lifted heavy weights—75 to 90 percent of their one-rep maximums for 8 to 12 reps per set—the other half lifted only 30 to 50 percent of their one-rep maxes for 20 to 25 reps per set.

Despite their different regimens, the men in both groups gained, on average, 2.4 pounds of muscle. Researchers also reported no significant difference between the two groups’ growth in the size of their muscle fibers.

How could this be? Turns out, when it comes to building muscle, your body’s response matters more than the type of exercise you do. Maximizing muscle growth requires activating as many of your muscle fibers as possible, study author Stuart Phillips, Ph.D., told Men’s Health. While you use your smallest (also called type I) muscle fibers for easy, day-to-day activities and light exercise, the larger, type II muscle fibers are used when the demand on your muscles increases and the type I fibers tire out. This study says you can activate those type II fibers by either increasing the weight you lift or the number of reps you do. To prevent muscle loss as you age, try these science-backed tricks.

“People say that lifting heavier loads is the only way you can recruit type II fibers, but that’s just not true,” Phillips says. “You can recruit type II muscle fibers by induction of fatigue.”

Of course, each approach has its pros and cons. Although lighter weights provide more options for exercises, they might not be as good at building strength in the long run, according to Phillips. On the other hand, heavy weights can be tough on your joints, tendons, and ligaments, so switching to lighter weights occasionally might give them a much-needed break. And don’t neglect this little-known muscle that can save your joints.

Although the study remains mum on the effects for women, research shows that weightlifting has loads of health benefits for both sexes.

Ready to get started? These upper body exercises to do with dumbbells are certainly worth a shot.

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