Muscles worked
The quads and glutes of your front leg do the main work, helped by the inner thigh and hamstrings. Unlike a dumbbell lunge, the bar runs on a fixed track, so you do not have to balance the weight. Your legs can work harder before balance gives out, but your trunk and the small muscles around your hips get less to do. Front foot placement shifts the emphasis: further ahead of the bar favours the glutes, closer underneath favours the quads.
Common mistakes
- Placing your feet by feel. The bar only travels straight up and down, so your feet must be right from the start. Try the stance with an empty bar and adjust until the bottom position feels good.
- Skipping the safety stops. Most Smith machines have stops that can catch the bar. Set them just below the depth where your back knee nearly touches the floor.
- Your back foot is flat. With the whole back foot down, the stance gets rigid and your back knee ends up in the wrong place. Stand on the ball of the back foot with the heel raised.
Variations and alternatives
- The dumbbell lunge demands more balance and works your trunk harder, for a freer movement.
- The Bulgarian split squat, back foot on a bench, also works in the Smith machine and moves almost everything to the front leg.
- The Smith squat uses the same machine with both legs, for heavier loads.
Sets and reps
With balance out of the way, you can go heavier than with dumbbells. To build muscle, 6 to 10 reps per leg over 3 sets works well, or 5 to 6 reps for heavier work. Do all your reps on one leg, rack the bar, then switch, as moving your feet with the bar on your back is awkward. The guide to sets and reps explains how to choose between heavier and lighter sets.
Measure the distance between your feet in foot lengths, so you set up the same way next session. Add 1.25 kg per side once every set is done, and add reps before the next increase. The fixed track makes progressive overload easy to follow, as every rep looks the same.