More weight means more muscle, right? But new research published in the International Journal of Sports Medicine shows that alternating between light and heavy weights may be the best way to build muscle and strength.
For the study, researchers followed 19 men as they completed eight-week strength training programs. Half followed a traditional three-day-per-week strength program, performing each of their sets with an amount of weight that allowed them to complete eight to 12 reps. The rest switched up their weights: They lifted near-max weight for two to four reps on the first workout day, moderate weight for eight to 12 reps on the second day, and light weight for 20 to 30 reps on the third day.
While both groups boasted big benefits, the lifters who varied their weights enjoyed an increase in bicep and triceps size and improved muscle endurance. They also experienced more gains in how much they could bench press. (Researchers expect similar results in women.)
Why? Lifting both extremely light and extremely heavy weight trains a wider range of muscle fibers than lifting moderate weights alone, says Brad Schoenfeld, Ph.D., C.S.C.S., assistant professor of exercise science at Lehman College in New York, and lead author of the study.
Let us explain: Your muscle fibers come in two flavors: type 1 and type 2. While type 1 fibers are best recruited with light loads and are in charge of endurance exercise, like lifting small dumbbells for 20 to 30 reps, it takes heavy weights to spring your type 2 fibers into action, he says. By tapping both types muscle fiber types, you get all of their benefits: size, strength, and endurance.
To get the most from your strength workouts, Schoenfeld recommends performing your exercises with a range of weight and reps. But you don't need to switch things up on a daily basis to get the benefits of varied-weight workouts, he says. Alternating weights on a weekly or even monthly basis will score you similar benefits—plus, they make your workouts easier to track.
One week or month, try lifting near-max weights for one to five reps per set. The next, transition to moderate weights for eight to 12 reps per set. For your last cycle, lift light weights for 15-plus reps per set, he says. Then, bask in the glory of your awesome muscles.