Leg extensions are an exercise that is usually performed from a seated position in a cable machine with a weight stack, although there are designs where weight plates are used in a lever system.
While exercises such as squats and leg presses are considered the most important for overall strength and development of the quadricep muscles (quads), leg extensions still have their benefits.
Benefits of leg extensions
As this isn’t considered a real mass building exercise, the rep range doesn’t have to be too low, with 12 to 15 reps being the most beneficial.
This allows you to focus fully on the contraction of the quads at the top of the exercise, and lift the weight in a more controlled manner.
Another benefit is that leg extensions are a great exercise for anyone just starting weightlifting or a fitness program.
This will help build up a level of strength in the quad muscles until they are ready to move onto heavier, multi joint free weight exercises such as squats.
Risk of injury
Having control over the weight is key to any effective exercise, but moving the weight too quickly on leg extensions can have other negative effects.
Over-extending happens when you extend your legs with the weight too quickly, the weight gains momentum and your leg becomes fully extended too quickly. This will put unnecessary pressure on your knee joint and risk potential injury.
As with any exercise, you shouldn’t include it in your workouts if it causes discomfort. While this may sound obvious it’s worth bearing in mind that different people’s bodies respond differently to different exercises. While you may read on fitness and bodybuilding forums that people have experienced knee problems or injuries in the exercise, injuries are possible with any exercise when performed incorrectly.
The best way to know if it is right for you is to perform a few sets on a leg extension machine yourself. Play around with the settings and the position of the seat to see if there’s a position that feels comfortable and can feel working your quads.
If you can’t find a comfortable position and you feel like the weight is putting too much pressure on your knees then this may not be the right exercise for you.
How to perform leg extensions
- Choose the weight you want to lift
- Sit on the padded seat and adjust the chair until your knee is just in front of the front edge of the seat.
- If you can adjust the angle on the padded rollers, then move them to an angle that will give you around a 90 degree range of motion from resting position to full extension
- If the height of the rollers can be adjusted, adjust the height of the padded roller(s) until the front of your ankles is pressing against them when you tuck your feet underneath
- As a general rule your toes should be in line with your knees. If they are further round towards the seat then this will put undue pressure on your knee joints at the start of the movement.
- If your leg extension machine comes with a lever and pad to rest on your quads to prevent you rising up in the machine then lower this into position now.
- If your leg extension machine doesn’t have this, then it should have a pair of handles, one handle on each side of the seat.
- With you sat firmly back in the seat, feet tucked under the leg rollers and gripping these handles this will be your starting position
- Fully extend your legs, focussing on your quadriceps to lift the weight and contract for a second at the top of the exercise
- Slowly lower the weight back to the start position
- Repeat for the required number of repetitions
- In terms of breathing, you should try to make sure you exhale on the extension and inhale as the weight is lowered back down.
Should you include leg extensions in your workout?
While it is generally accepted that leg extensions should not be the only exercise you do to fully develop your quads, it is still an effective isolation exercise for developing the muscle. This exercise should really be thought of as more of a finishing move to your leg workout.
An isolation move that comes after the main heavy compound movements, much like performing cable bicep curls after free weight barbell curls or cable crossovers after barbell bench presses.
Squats and leg presses are the two main exercises that you should focus on if you are looking to build more well developed leg muscles, but leg extensions should still be included at a position in your workout that will work the muscle most effectively.
So positioning of the leg extension in your workout has some importance, but why? This really depends on your own strength level. The leg extension machine is exactly that, a workout machine usually with a maximum resistance set by the weight stack. If you have very strong quad muscles already then performing leg extensions first may lead to you being able to comfortably perform 12 or 15 reps even with the maximum weight for multiple sets.
In this case the exercise loses most of its effectiveness. While it will pre-exhaust your quads for the mass building exercises later in the workout, it doesn’t meet the requirement that any exercise has to be considered effective. It doesn’t provide progressive resistance.
What I mean by this is that while you may increase the repetitions over time, there will be a limit where they simply aren’t beneficial. If you are taking 3 or 4 minutes per work set because you need to perform 40 leg extensions just to get the quad muscles to failure then this isn’t what we are trying to achieve.
Here are just a couple of the situations when leg extensions will be beneficial:
Splitting leg workouts over multiple days – While many of us are limited on the amount of time we can get to the gym, for those who can train more frequently you may split leg training over two days. One day for working the quads and glutes and one day for working hamstrings and calves.
In this case you would be more likely to try to keep the work off your hamstrings but still work your quads to failure, such as with front squats and leg extensions.
Taking the pressure off your lower back – A lot of workout plans include both deadlifts and squats across the week. If you have performed deadlifts earlier in the week and now just finished your sets of squats, you may not want to put more pressure on your lower back with hack squats or leg presses.
Leg extensions being an isolation exercise put you in a seated position to take any movement or stress out of your lower back.
Other effective exercises for quadriceps
As with any exercise, knowing whether or not you should add it to your workout really relies on the answer to two questions. Does it follow my body’s natural range of motion and can it provide progressive resistance so I can increase the weight and intensity over time.
If the answer to both of these questions is yes then there is no doubt that it can be added to your workouts and be effective. Knowing when to include it in your workout to see the most benefit is the next question. If you are already approaching the limit of the preset weight in the leg extension machine then perform the exercise after your main leg press, squat or other mass building exercises.
The only situation where you should really think about adding an isolation exercise at the beginning of a workout is when recovering from an injury, or if you are new to weightlifting. If you are just starting your first workout program you will most likely be looking to build up muscle and support around the joints before attempting multi joint compound movements, such as back squats and military presses.