Should you lift heavy or light weights to build muscle better?

Whether you should lift heavy weights or light weights, and how many reps you do, is a long-standing debate in the fitness world. Here’s the science

Woman doing deadlift
(Image credit: Getty Images)

Do you really need gigantic heavy dumbbells to build muscle, or can you do it with smaller weights and higher reps? When we first think about building muscle, we think of cartoonish images such as Arnold Schwarzenegger hefting heavy weights in Pumping Iron, and similar images of bicep curls with heavy plates. 

However, building muscle isn’t all about the size and weight of the, well, weights. You can build muscle with smaller weights, or even just your own body weight, especially if you are a beginner. It’s one of the reasons the best adjustable dumbbells are so popular, as they allow you to switch between light and heavy weights depending on your workout needs. 

Below, we’ll break down the science on why you may need to rethink whether you’re lifting heavy weights vs light weights.

Heavy weights vs light weights: low or high reps

For experienced lifters, heavy weights are still essential for getting stronger. However, if you are just starting on your muscle-building journey, there's plenty you can get done by sticking with lighter weights.

A study published in the Journal of Applied Physiology looked at 49 lifters who used lighter and heavy weights to encourage strength and muscle growth. Both groups "trained to failure", until they physically couldn't complete the exercise anymore. While the lighter weights obviously took the participants a lot longer to get to this point and they had to perform more repetitions, the study found similar results could be achieved with both light and heavy weights. 

Both light and heavy weights induced muscular hypertrophy, which is an increase and growth in muscle cells. 

However, another study examining 18 young men looked at high-load, lower-rep resistance training protocols versus lower-load, higher-reps – eight-12 repetitions for high weights versus 25-35 repetitions for low weights. The researchers found that both low weight and high weight induced similar states of muscular hypertrophy, but using high weights is better for “maximizing strength adaptations”, or improving how much weight you can lift in one go.

So while you might be able to grow your muscles with light weights, lifting heavy weights is the best way to get stronger.  

barbell on gym floor

(Image credit: Delaney Van/Unsplash)

Heavy weights vs light weights: Making the most of what you have

If you aren’t a member of a gym or don’t have heavy weights to hand, you can make the best of things with bodyweight training and light weights. If you lift something heavy, you often struggle to maintain control, lowering your weights very quickly once you reach the apex of the lift. 

Not so if you try using less weight. You're able to lower your dumbbell, barbell, or body under control, which contributes to the muscle-building process. The process of lowering your weight is known as the "eccentric phase" of a muscle-building movement, and the slower and more controlled you're able to make it, the more strength you'll build. It's as important as the actual lifting phase, according to the journal Frontier Physiology. It's also much safer for beginners to use a weight they know they can lift and lower easily: heavier weights lifted without good form lend themselves to a greater risk of injury. 

Another safe alternative is to use lightweight, high-tension elastic resistance bands instead of heavy weights. Check out our guide to the best resistance bands for the lowdown on how. 

The bottom line is that heavier weights make you stronger, but you’re still able to grow your muscles even if you only lift light weights – up to a point. Eventually, your body will adapt to the amount of weight you’re lifting, and you’ll have to challenge it in new ways. 

If you're training with weights, try lowering the amount you lift and focusing on form, performing the movement slowly, to reap the rewards. If you only have light weights to hand, focus on slow, controlled movements using more repetitions to increase muscular hypertrophy. 

If you’re using your body weight, try lowering yourself into a push-up, or down from a pull-up, as slowly as you can to really build that strength. Over time, you can adjust how you perform the movement: for example, doing one of the variations in our how to do a push-up guide allows you to hit muscles you may be excluding right now

Matt Evans
Matt Evans

Matt Evans is an experienced health and fitness journalist and News Editor at Fit&Well, covering all things exercise and nutrition on the Fit&Well website. Matt originally discovered exercise through martial arts: he holds a black belt in Karate and remains a keen runner, gym-goer, and infrequent yogi. His top fitness tip? Stretch.