Leg Extension

What is the leg extension?

The leg extension is an isolation exercise using a machine to lift and lower the lower leg by bending the knee. During the exercise, the upper leg is held firmly in place by a special pad.

What muscles does the leg extension use?

Leg extensions target the front thigh (quadriceps). As the leg extension is an isolation exercise, the quads alone are targeted with this lift when it is performed correctly, with a properly adjusted seat and pad.

The quadricep muscles work as a pair alongside the hamstrings, working to flex and extend the legs. When you bend your leg you use your hamstrings and when you straighten it, you use your quads.

By straightening your leg out using the leg extension machine, you work your quadriceps in an excellent isolation motion.

Leg extension machine

Benefits of the leg extension

Benefits of the leg extension include well developed quadriceps and, when paired up with the leg curl, a well balanced leg physique.

Leg extensions are an excellent choice of lift to complement the leg curl. This is because this extension exercise works the opposite muscles to the curl exercise, thereby creating balance and great posture for the lower body.

This lift is a great isolation exercise for fine tuning the development of the quads and increasing definition in this area.

The quads are used all the time in daily life for exercises such as walking up stairs, so using this extension lift regularly will help make regular activities easier as your muscles gain in strength.


Many people like the look of well developed quads as the thigh can get a defined muscle along the length. As with all isolation exercises, best results will be obtained by using this lift as an extra on top of compound lifts which work the whole of the legs, such as the leg press or squat.

Leg extension positioning

Good leg extension technique means focusing not only on the exercise itself but also on your starting position. Make sure your legs are correctly placed and your seat and pad is adjusted properly so that you can concentrate on the lift and get the most benefits from the exercise.

Before performing the leg extension, you need to adjust the back rest and pads so that you are in the correct position. Exactly where you need to move them to will depend on your own height and body proportions.

The back rest should be moved so that the centre of your knee is in line with the pivot point on the machine. You should be sat fully upright with your bottom tucked well into the seat.

The ankle pad should sit on top of the shoe laces, just at the bottom of the shin. If an option on your machine, the range of movement should be set to just under 90 degrees.

leg extension machine

Performing the leg extension

To begin the leg extension, place your feet about a hip distance apart under the ankle pad, toes pointing forwards and hips, ankles and knees all aligned.

Straighten the leg fully when extending to lift the weight, but do not lock out the knees at the top of the lift. Your toes should point to the ceiling at the top of the lift.

Throughout the movement, the abs should be engaged, with a neutral spine and chest out. This position helps you maintain leg extension technique throughout the lift.

Leg extension technique

As you lower the weight, bend the leg to no more than 90 degrees to finish your rep, then begin to straighten again as you lift into your next rep. Once you have completed your last set, bend your knees to gently return the weights to the stack.

Good leg extension technique requires the right positioning and a slow and controlled motion. By taking care over technique on isolation lifts you can enjoy the most benefit from the exercise with each lift giving your muscles a good workout.

Poor technique always brings poor results, so focus on leg extension technique for this exercise and combine it with the leg curl for maximum gains. Read more about the leg curl – the perfect complementary exercise to the leg extension.

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