You've heard this rule before: always, always, always use a full range of motion. The truth? Once you're past the newbie stage and your goal is muscle growth, partial reps have their place.
Why the Rule Was Created: Going through a full range of motion is most optimal for hypertrophy and forces beginners to master basic control and ensure adequate mobility.
Why You Should Break It: Partials shouldn't make up the majority of your training, but supplementing with them can be wildly effective.
Some exercises do produce greater hypertrophy when cutting the ROM. This is because a full range can significantly unload certain portions of the lift like lying skull crushers. They also allow for additional volume by extending a set, further stimulating growth. They can also force you to train a specific ROM that might be a sticking point. If you're having a hard time getting a particular muscle to grow you can use partials to activate and emphasize a specific muscle on a compound lift. According to Christian Thibaudeau, "Do this by keeping reps only in the range of motion where the target muscle is doing most of the work by itself. You want to avoid going into the transition zones where other muscles start to take over so that maximum tension is maintained on the target muscle.” If you're too caught up in always lifting in a full range, you're leaving gains on the table. When you mature in your training, adding in partials is exactly what you need to induce more growth or break through a sticking point.