Cheat reps—that is, getting the weight up with little to no regard to form—can be a useful way to induce more muscular fatigue when doing accessory exercises, like barbell curls or lateral raises.

Muscles need to perform a designated amount of work to yield muscular development, and cheat reps can help you finish reps on a set that was started with precise form. That being said, they shouldn’t be done with compound moves, like deadlifts or back squats. They can cause damage to major joints. Those moves require picture-perfect form for proper muscle recruitment and to minimize joint vulnerability.
Similarly, avoid them on the barbell row, preacher curl, dumbbell pullover, and dips, as a lot of damage can happen from trying to cheat past form.

Never cheat on moves like preacher curls (shown above). Doing so could injure your joints, in this case your elbows, as you’re locked in. However, standing barbell cheat curls are fair game.

 David Otey, C.S.C.S., is a personal training manager at Equinox Sports Club in New York City.