3 Myths About Muscle-Building

Learn three muscle-building myths and discover the shocking truth about building muscle  and getting fit.

Ben Greenfield
5-minute read
Episode #256

After being steeped in the fitness industry for more than a decade, I’ve seen many fitness fads come and go, and I’ve also seen many fitness myths dispelled. But there are still a few myths floating around among personal trainers, believed by exercise enthusiasts, and found in those fancy fitness magazines in gyms and health clubs. These myths could be holding you back when it comes to building muscle. 

Myth #1: You Need to Lift Heavy Weights to Build Muscle

It’s certainly true that an excellent way to build muscle is by lifting heavy weights with big compound exercises, such as squats and dead lifts. But it’s not the only way to go. Contrary to popular belief, you can gain muscle using light weights (or body weight) and higher reps. 

For example, one study compared the effect of high reps and low reps on muscle growth, comparing sets performed with 80% to complete muscle fatigue with sets performed to 30% to complete muscle fatigue. It turns out that the load is not important, but simply whether or not a muscle is actually worked to fatigue, and in this study, high reps and light weights stimulated just as much muscle growth as low reps and heavy weights. So yes, this means you can, for example, build chest muscles by skipping three sets of eight reps on a bench press, and instead doing a few sets of high-rep push-ups to complete failure (which is good to know if you’re stuck working out in a hotel room or living room, have no access to a bunch of steel, metal, and weight plates, and still want to build muscle!).

There are plenty of other studies that back up the muscle-building capabilities of high-rep, low-resistance training. In this study, light super-slow lifting at 55-60% of the participants one rep max (1RM) increased both muscle thickness and maximal strength just as much as heavy normal-speed training performed at 80-90% of 1RM. In this study, both heavy training with 8-10 reps and light training with 18-20 reps activated the genes involved in muscle growth.

Another study found that training with higher reps and lighter weights (25-35 reps) led to the same gains in muscle size as heavier weights with 8-12 reps. Even in seasoned weightlifters, researchers found the same muscle growth occurs when comparing 20-25 reps weight compared to 8-12 reps with a heavy weight.

Additionally, in this study, high reps and light weight (24 reps with 30%) increased post-workout protein synthesis, a sign of muscle building and hypertrophy, for 24 hours after exercise, and it did this to a far greater extent than low reps and heavy weights using 5 reps and 90%. In yet another study, low weight training, even when not performed to complete muscular fatigue, stimulated protein synthesis (a sign that connective tissue is better capable of repairing) in connective tissue just as much as heavy weights.

Ultimately, if you want to add muscle mass as fast as possible, lifting heavy weights is the way to go. But you can still build muscle with light weight and high reps. Incidentally, as this study and this study shows, this approach seems to be most effective when training the legs vs. the upper body.


About the Author

Ben Greenfield

Ben Greenfield received bachelor’s and master’s degrees from University of Idaho in sports science and exercise physiology; personal training and strength and conditioning certifications from the National Strength and Conditioning Association (NSCA); a sports nutrition certification from the International Society of Sports Nutrition (ISSN), an advanced bicycle fitting certification from Serotta. He has over 11 years’ experience in coaching professional, collegiate, and recreational athletes from all sports, and as helped hundreds of clients achieve weight loss and fitness success.