Lunges and split squats share similarities that make the two exercises easy to confuse. To understand the differences between them, focus on the muscles they activate and the form considerations of each. The differences may appear subtle, but the exercises differ significantly. Contrasting the two focuses your workout to support your fitness goals.
The Rear Leg is Key
In a lunge and split squat, one leg is forward and in front of you, the other leg is behind you. In a lunge, the rear leg is engaged in the exercise. In a split squat, the rear leg is at rest throughout the exercise -- it is not engaged. This is the key difference between the two exercises. A split squat focuses on the exercise entirely on one leg. The lunge uses both legs at the same time.
Static or Active Axis
In both a lunge and a split squat, you move the weight -- either your body weight or body weight with additional weight added from a barbell or dumbbells -- up and down along the axis created by the position of your legs. In a split squat, however, that axis is static. Once you've found the right position for your working leg in relation to your resting leg, you descend and return to starting without moving your feet. Lunges are different. While you can echo a split squat in terms of creating a static placement of your feet if you have balance issues, lunges typically involve stepping either forward or back.
Feeling the Exercise
Split squats and lunges are both lower body exercises that focus on the gluteal muscles that make up your bottom as well as the fronts and backs of your thighs, the quadriceps and hamstrings. In addition, both exercises work the calf muscles and core. However, the intensity of your work out varies between the two. Because the split squat uses only one leg at a time, it's a more focused exercise targeting these muscle groups. A lunge balances the load between both legs, making it less fatiguing to the muscles.
Watching Your Form
One component that's common to these two exercises is the critical nature of form. Incorrect form for either of these exercises is a significant hazard to your back and knees. When descending, you should align your knee to your second toe. If you don't, you are at risk of injuring your knee. Move your front foot forward to avoid overextending your knee and rotate your foot slightly to ensure proper alignment. In addition, watch the position of your chest and shoulders. Don't bow forward. Keep your torso raised in both exercises to avoid over-working your back muscles. Both exercises engage the erector spine muscles that support your torso. Don't overwork those muscles by hinging forward from the hips or waist as you descend. If you're bowing, brace your core more consciously to support your back and lift lighter weights to ensure your legs are getting the focus of the work out, not your back.