Leg extensions and dumbbell lunges are strength exercises that target muscles in your lower body. They both work your quadriceps, the muscles on the front of your thigh, but this is where the similarities stop. The lunge is a compound exercise that works several muscle groups; the leg extension is an isolation exercise that targets one muscle group.
Leg Extension
To do the leg extension exercise, sit in a leg extension machine and place your ankles under the leg pad. Start with your knees at a 90-degree angle. Exhale and extend your knees, lifting your lower legs. Stop when your legs are almost fully extended. Keep a slight bend in your knees; do not lock your knees. Pause for a count and then slowly lower your legs back to the starting position.
Dumbbell Lunges
To do a dumbbell lunge, stand upright with a dumbbell in each hand. You can hold the dumbbells at your sides or up by your shoulders. Step forward with one foot and bend both knees to drop down into a lunge. Stop descending when your front thigh is parallel to the floor; your back knee should be a couple inches above the floor. Exhale and press through your front foot to power yourself back up to a standing position.
Function
The leg extension is an isolation exercise, while the lunge is a compound exercise. Isolation exercises involve movement at only one joint and target one muscle group. For the leg extension exercise, the movement occurs at the knee joint. This targets the quadriceps muscles. Compound exercises involve movement at two or more joints and work more than one muscle group. For lunges, the movement occurs at the knee and hip joints. Dumbbell lunges work several muscles, including the quadriceps, hamstrings and gluteus muscles.
Considerations
You can do leg extensions with other equipment, such as a cable machine or resistance bands. The movement is the same regardless which form of resistance you choose. Lunges have several variations. You can do reverse lunges, walking lunges, side lunges, forward lunges or stationary lunges. If you have time for only one of these two exercises, choose lunges since they work more muscles.
