The leg extension is a basic strength exercise that targets the quadriceps, a group of four muscle heads on the front of the thigh, mainly responsible for knee extension, or straightening the knee joint. This single-joint exercise is typically performed on a leg extension machine, but if you work out at home and don't have access to an exercise machine, you can use free weights to do the leg extension exercise.
Be Smart, Use a Dumbbell
All you need to do the leg extension exercise is a dumbbell and a chair. Sit on the front edge of the chair and grab the sides of the seat. Hold the dumbbell vertically between your feet so the top end of the dumbbell rests against the top of your feet. Lean back slightly, but keep your back straight. Lift your feet so the dumbbell isn't touching floor. Your lower legs should be perpendicular to the floor. This is the starting position. Extend your legs by straightening your knees until your legs are about parallel to the floor. Pause before slowly lowering back to the starting position.
The Dumbbell Has Limitations
Although an effective quadriceps-strengthening exercise, the dumbbell leg extension exercise has limitations. It can only be done with both legs simultaneously. You cannot work each leg independently. As your legs become stronger, you will need to use heavier dumbbells to progressively overload the muscles and it can be challenging to hold a large, heavy dumbbell between your feet.
With the band leg extension exercise, you can work one leg at a time. Attach the band to an anchor point behind the chair and attach the other end of the band around your ankle. If available, use a band with an ankle cuff. Perform the exercise in the same manner as the dumbbell extension, but work one leg at a time. Place the chair far enough away from the anchor so the band is taut and provides resistance.
The leg extension exercise doesn't work the hamstrings, the muscles on the back of the thigh. Other popular leg exercises, including squats and lunges, work both the quadriceps and the hamstrings, but the quadriceps are more active and dominate these movements. This overemphasis on pushing exercises leaves the hamstrings weaker and undertrained compared to the quadriceps, negatively impacting sports performance and increasing your risk of muscle tears. When developing a leg routine, create balanced workouts that train all the muscles of the legs.