The deadlift is a must-have exercise to build total-body strength, pack on slabs of muscle, and sculpt an awesome physique. When done right, it strengthens the muscles at your hips, hamstrings, and back that are essential for athleticism and overall fitness. (Heck, it can even improve your posture.)

But walk through any commercial gym and you’ll struggle to spot a clean deadlift. Poor technique makes the exercise harder and increases chances for injury—because the deadlift involves such heavy weights the margin for error also skyrockets.

Matt Kasee, MS, C.S.C.S., owner of Matt Kasee Training and Performance (and an over 500-lb. deadlifter), helps us dissect the worst deadlifting mistakes—why they’re bad and exactly how to avoid them. Don’t be surprised if you can pull much more weight with less pain the next time you deadlift.