Pack on Monster Muscle: Partial vs. Full Reps Debate

Will Partial Reps Increase Arm Growth?

By: Robbie Durand

Walk into any gym and head over to the leg press machine and chances are you will see a guy with every plate on the leg press. To the novice lifter, one would think this is an excellent way to build muscle. It makes physiological sense that if you overload a muscle, it’s going to grow. That’s why all those heavyweights are in the gym, to cause muscle damage and spur new muscle growth. It makes sense that using a heavier weight is going to cause more muscle damage and result in more muscle growth. Here are a few studies which may change your mind about using partial reps.

Study # 1: Partial vs. Full Reps Muscle Activity

The earliest studies looked at the muscle activation of full and partial ranges of motion. Not surprisingly, the execution of a full range of the movement elicited the greatest muscle EMG activity. So the based on this study, using partial reps is not going to fully activate the muscle like doing a full range of motion. Using a full range of the movement is going to activate more muscle fibers and lead to better muscle growth.

Study # 2: Partial vs. Full Reps Muscle Damage

Let’s get back to the guy who loads up every weight in the gym on the leg press, is he going to stimulate maximal muscle damage. Researchers examined subject’s markers of muscle damage after full and partial reps during bicep curls immediately, 24 hours, 48 hours and 72 hours after exercise. The weight lifted in the partial range of motion condition was 40% higher compared to the full range of motion. Despite the 72 hours after exercise, the full range of motion condition led to significant higher soreness sensation in the biceps. In conclusion, bicep exercise with full range of motion seems to induce greater muscle damage than partial range of motion exercises, even though higher absolute load was achieved with partial range of motion.

Partial vs. Full Reps for Muscle Growth

So a couple of scientists wanted to test if loading up the bar is going to result in greater increases in muscle mass and strength. Forty untrained subjects were placed into one of three groups:

-Full repetition range,
-Partial repetition range, or
-Control group.

Biceps were trained using preacher curls on a machine. The partial rep group restricted their range of motion to half of the movement. The weight used was not equal for both groups, however, as the partial group did not have to fully extend, so the amount of weight they were able to handle for the target reps was higher than the full group could handle. One would expect that the group that used heavier weight would have greater increases in muscle mass, but after ten weeks, the full range of motion group had increased their one-rep max by 25.7% above where they’d started. The partial repetition group had increased their 1RM only 16% over baseline. When it came to muscle size, again, the full repetition group that used a lighter weight had slightly greater increases in muscle size than the group that did partials.

Key Points: Using a full range of motion results in greater muscle damage, muscle activity, and muscle mass despite a lighter weight being used. Don’t leg your ego get the best of you in the gym, using a lighter weight and a full range of motion is the best way to train.

Baroni BM, Pompermayer MG, Cini A, Peruzzolo AS, Radaelli R, Brusco CM, Pinto RS. Full range of motion induces greater muscle damage than partial range of motion in elbow flexion exercise with free weights. J Strength Cond Res. 2016 Jul 7.

Paoli A, Marcolin G, Petrone N. Influence of different ranges of motion on selective recruitment of shoulder muscles in the sitting military press: an electromyographic study. J Strength Cond Res. 2010 Jun;24(6):1578-83.

Pinto RS, Gomes N, Radaelli R, Botton CE, Brown LE, Bottaro M. Effect of range of motion on muscle strength and thickness. J Strength Cond Res. 2012 Aug;26(8):2140-5.