Should you lift heavy or light weights to build muscle?

Heavy weights or small ones? Lots of reps or a few intense lifts? We break down the science of strength

Man lifting a heavy barbell to build muscle
(Image credit: Getty Images)

Are you looking to build muscle over the winter? It's common sense to know that resistance training – whether it's in the gym, at home, using weights and machines, or just calisthenics – is what you need to help you pack on strength and size. However, there's a lot of conflicting guidance on exactly you go about lifting weights. 

It may seem like a silly question, but when you're confronted with an array of weight-plates for barbells, or you unpack the best adjustable dumbbells or best resistance bands at home, it's surprising how difficult this choice can be. Do you go as heavy as you can and do what seems like a comparatively small amount of repetitions at high intensity, or do you go light and train for volume? Or do you go somewhere in the middle?

Researchers from the University of Central Florida looked at resistance-trained men and what provided the most muscular size and strength: volume (low weight, high reps) or intensity (high weight, low reps). Participants were assigned to two groups: one group who trained at 70% of their maximum lift for 10-12 reps, while another group trained 90% of their maximum lift for 3-5 reps. 

The researchers measured thickness and strength of several muscle groups, and one-rep maximum lifts after the eight-week programme had finished in order to determine which group gained the most strength. 

trap bar deadlift

(Image credit: Sergio Pedemonte/Unsplash)

It turns out the group who trained for intensity, with 90% of their maximum lift, did better both in gaining lean mass and increasing their strength than those who lifted lighter, for longer. The group who trained with 70% of their maximum capacity also saw improvements, of course, but not as dramatic as their counterparts. When it comes to resistance training, the answer seems to be "go big or go home".

Of course, if you're coming to resistance training for the first time, this could all sound a little intimidating, but you don't need to be an expert in the squat rack to see improvements. Instead of doing sets of 10 bicep curls, try adding more weight and doing five instead. Opt for compound moves such as the deadlift, bench press and squat, three key exercises which have been found to increase the release of growth hormone in the body.

The reason these are called compound exercises is they work multiple muscle groups, rather than isolation exercises such as the bicep curl which only work one set of muscles. Compound lifts often use your whole body, making them extremely efficient at building muscle and increasing your metabolic rate, according to research published in the Journal of Physical Therapy Sciences.

If you'd like to get started doing compound lifts in the gym, it's well worth perusing our guides to how to deadlift properly and how to do a barbell squat. And, of course, if you're looking for some weights for home, be sure to check out the Black Friday weights deals this year.

Matt Evans
Matt Evans

Matt Evans is an experienced health and fitness journalist and Channel Editor at Fit&Well. He's previously written for titles like Men's Health and Red Bull, and covers 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 kickboxer and runner. His top fitness tip? Stretch.