Do High-Reps Increase Chest Size?

fitness portrait of a muscular male shirtless chest as he lifts weights

A classic prescription for a bigger chest is to perform three to six sets of pectoral-focused exercises for eight to 12 repetitions at a weight that is 80 to 85 percent of your one-repetition maximum. Performing 20 or more repetitions of the most effective chest exercises may increase chest size as significantly as a traditional low-rep, high-load routine. Working to fatigue seems to be the key in stimulating muscle growth.

How Muscles Grow

When you perform resistance training, your body receives a signal that the cells in your muscles have been traumatized. Your system then sets out to repair the muscle and make the muscles grow stronger to prevent trauma in the future. This repair process makes your muscles grow stronger and, under the right conditions, larger. High loads provide significant trauma to the muscles, stimulating repair and growth, but research suggests that low loads lifted for a high number of repetitions may also trigger enough trauma to induce muscle growth.


A study published in a 2012 issue of “Applied Physiology, Nutrition and Metabolism” had young men perform strength-training workouts with weights that were only about 30 percent of their one-repetition maximum. They did 25 or more repetitions to induce full muscle fatigue. The McMaster University researchers found that this training protocol was equally effective in stimulating the muscle rebuilding process as a high-load, low-rep routine. An earlier study, published in the August 2010 issue of “Plos One” similarly concluded that low-load, high-volume resistance exercise is as effective or even more effective in stimulating muscle anabolism, or growth, when compared to high-load, low-volume training.


When applying a high-load regimen to the chest, include the most effective pectoral exercises. A study that was sponsored by the American Council on Exercise and published in 2012 named the bench press, the pec deck machine and bent-forward cable crossovers as the exercises that stimulated the most muscle fibers in the chest. A high-rep routine of these moves using lighter weights can help you build your chest size, but you must work to fatigue. Fatigue is the sensation you feel when you cannot do another repetition with good form.


No guarantee exists that any particular training protocol will create a massive chest. Muscle growth also depends on genetics, diet, sleep and hydration. Changing up your routine regularly can also help your chest grow. Consider alternating a four-week, high-rep and low-load routine with a four-week high-load, low-rep routine to keep your muscles from becoming too accustomed to a certain protocol.