Squats of any type, whether with free weights or on a Smith machine, can be dangerous if they’re performed incorrectly. The most common free-weight mistake people make is leaning their upper body too far forward, which shifts weight distribution from the hips and thighs to the knees and lower back.
It’s difficult to make this error on a Smith machine though, because the barbell is in a fixed vertical plane. However, the very fact that the machine allows less freedom of movement can also set you up for injury: If you don’t lean far enough forward during a squat, you can strain your back and knees.
So which approach is best? Exercise scientist Shawn Arent, PhD, from Rutgers University recommends free-weight squats because you’ll activate more stabilising muscles than you would with a Smith machine. But Arent says to squat without weights to enforce correct form: With your feet slightly wider than your hips, chest up and knees in line with your toes, lower your body by pushing your butt back and bending your knees simultaneously, until your thighs are at least parallel to the ground – deeper is better. Flex your hips and knees at the same time and don’t round your back. Once you’ve got this down pat, do a few warm-up sets of squats with 50-75 per cent of your targeted load before beginning your full routine.