Low Weight, High Reps: Does It Work to Build Strength?

If you're new to weight-training, you may wonder what the best approach is when it comes to building muscle. Is power lifting, with heavy weights and fewer repetitions, the way to go? Or lighter weights and a high number of reps?

HSS sports medicine physician Jordan Metzl, MD, is in the low weight/high rep camp. “We used to think that doing low reps of a very high weight was the best way to build muscle,” he says. “But increasingly we are learning that it may be more efficient to do a high number of repetitions with less weight.”

In addition to taking care of athletes of all ages and abilities at HSS, Dr. Metzl is also the author of several books on exercise and fitness. Here, he talks about the importance of maintaining strength as you age and the best way to do it.

Focusing on Fast-Twitch Muscle Fibers 

Everyone has a combination of slow-twitch (also called type 1) and fast-twitch (also called type 2) muscle fibers. Slow-twitch muscle fibers are important for endurance, whereas fast-twitch fibers enable sudden bursts of energy. “As we age, we lose the fast-twitch fibers,” Dr. Metzl says. “Strength training is a great way to build and maintain these muscle fibers. And the stronger you are, the better you are able to support your skeleton. This in turn will lead to less pain in your body, especially in your back and knees.”

He adds that maintaining muscle mass is especially important for people who do sports like tennis, basketball, and skiing — both for building better endurance and for preventing injury.

The loss of muscle mass, called sarcopenia, is a common problem, especially as people get older. “We are increasingly learning that muscle mass has benefits not only for movement, but for metabolism,” Dr. Metzl says. “People need to commit to building and maintaining strength throughout their lives.”

Low Weight, High Reps Is Good for Overall Health

Strength-training workouts that employ low weights and high reps are good for your heart and lungs as well as building muscles. This includes high-intensity interval training (HIIT) workouts, which entail alternating between pushing your body hard and taking short breaks.

Studies have shown that oxygen consumption, a good marker of cardiovascular benefit, is higher during 30 minutes of high-intensity weight training than it is during 30 minutes of running on a treadmill. HIIT workouts can also help control and improve blood glucose readings, a measure of diabetes risk.

Workouts that use low weight with higher reps are also safer. If you try to lift weights that are too heavy, you are more likely to cause a muscle tear or strain. You can use signals from your body to figure out what size weights to use for your workout. For an exercise like bicep curls or dumbbell rows, you should be able to do 8 to 10 reps, Dr. Metzl says. When you get to the point that you can do 15 reps without much difficulty, then it may be time to go to a higher weight.

It’s Important to Work Out Your Whole Body

“I encourage people to focus on total-body workouts, which work the lower body, middle body, and upper body,” Dr. Metzl says. One example of this would be squats (with or without weights) to work the lower body, planks to work the middle body, and bicep curls to work the upper body.

As with any workout, if you’re starting from square one, it’s good to check in with your doctor before beginning. “If you’re planning to ramp up your physical activity, it’s good to get a general checkup to find out how hard you should push yourself based on your physical condition,” Dr. Metzl says. “It’s also good to get baseline numbers for things like your blood pressure and cholesterol. That way you can see how well you’re doing as you improve your fitness.”

“I don’t want people to feel intimidated about weight training,” Dr. Metzl concludes. “I feel strongly that anyone can do these kinds of workouts.”