Partial reps are very common in a gym – whether that be intentional or unintentional. Partial repetitions occur when a lifter utilizes only a portion of the entire range of motion available. For example, look at the bench press. A normal range of motion for bench press is starting with elbows locked out at the top, touching the barbell on the chest, then returning the barbell to the locked out position. A partial repetition would be completed if the range of motion was shortened to a non-locked out position of the elbows.
At first glance partial reps may seem incorrect, but These “half reps” can be beneficial and lead to strength or muscle gains when used correctly. For instance, utilizing partial repetitions could be necessary for advanced lifters who have reached a plateau and would like to overcome it. Specifically in the bench press, you could load a bar to more than 100% of the weight you can lift through the full range of motion, and concentrate on the lowest portion of the movement, providing a “Supra-maximal” stimulus to increase strength in that range. Obviously, a good spotter is essential when utilizing this technique.
The over-utilization of partial repetitions could lead to shortening of soft tissue and ultimately the restriction of normal range of motion. So be sure to choose their implementation them wisely!