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You’ve probably seen those large athletes with massive thighs at the gym using a leg extension machine. Truth be told, the seated leg extension machine is a great piece of exercise equipment for anyone looking to get some thick thighs. And, it’s pretty easy to use.
If you’re thinking of adding a new machine to your leg day routine, take a look at some of our tips on how to perform a leg extension.
What is a leg extension machine?
The seated leg extension machine pumps your leg muscles. Your legs fit under a roller or pad and as you extend your knee joint, the pad moves upwards. The roller or pad is attached to a weight load. Some machines have inclined seats and some up more upright. Regardless, the range of motion of your knee extension is from 0 to 90 degrees.
Open kinetic chain exercises (OKC) are those that allow the movement of the target body part. While closed kinetic chain exercises (CKC) are ones in which the body part is stationary. Because you’re moving your legs around a pivot point, the leg extension movement is an open kinetic chain exercise.
Which muscles are used in a leg extension?
The leg extension machine isolates movement only in the quadricep femoris muscles. The quadricep muscles is a big group of 4 leg muscles on the front portion of your legs. These include the rectus femoris, vastus lateralis, vastus medialis and the vastus intermedius muscle.
Because of the angle range of the leg extension movement, different muscles are activated either more or less at specific knee angles. One study proved this by placing a group of men and women on a leg extension machine and measuring their quadriceps muscle peak torque and activation at 30, 60 and 90 degree angles. The muscles studied were the rectus femoris, vastus lateralis and vastus medialis. Contrary to other previous research, for both men and women, it was found that the vastus medialis reached its maximum activation at 60 degrees. The activation of the vastus medialis then decreased at 90 degrees and further decreased at 30 degrees.
Surprisingly, the vastus lateralis and rectus femoris activation in both groups didn’t show a significant change between angles. Having said that, the values of muscle activation of the vastus lateralis in males were 2 times or greater than that of the vastus medialis activation in women, at all 3 angles. This fact means that there could be more muscle imbalances between the vastus lateralis and vastus medialis in women, which could make them more susceptible to injuries.
Considering all of this information, if you’re planning on using a leg extension machine, it’s important to exert caution because too much weight may put a lot of pressure on your knee joints. Additionally, the correct movement and adjustments are needed to further avoid injuries.
You shouldn’t be solely relying on using a leg extension machine to get buff legs. With continued use, you’d be strengthening only the quadriceps muscles. This would create muscle and movement imbalances which in turn, will make you more prone to injuries. The lower limbs are made of numerous muscles that all need to be equally strengthened for optimal mobility and athletic performance. So, try not to limit yourself by using only an extension machine. You should be incorporating other leg exercises to reach your full potential.
How to perform a seated leg extension
Now that we’ve covered the science behind the movement of a leg extension, we’ll take you through the proper steps to use the machine correctly.
First off, try to familiarize yourself with the machine. Look for the knobs and the pivot point to adjust the seat and leg pad accordingly. Adjust the back pad and seat so that when you’re sitting, your knees are aligned with the pivot point of the machine. Next, you need to position the leg pad or roller so that it sits nicely on your ankle joints. It should not be resting on your lower legs. Also before you begin, check the type of weight load on the machine and that it’s set up properly. It may be weight plates or a weight stack. We can’t tell you how many times we’ve seen a pin precariously balancing halfway out of the weight stack. If the weight falls, you can do some serious damage to your body. And on that note, choose a lighter weight to start until you master the movement and exercise.
Position yourself on the seat and with your legs beneath the pads at a slightly larger angle than 90 degrees. If need be, you can adjust the lever to feel comfortable. That way, you’ll be putting less stress on your knees.
Hold onto the handlebars on either side of the seat. While exhaling, lift the weight load by extending your legs. During the movement, focus on sitting as far back as possible on the backrest, engaging your core muscles and squeezing your quads. Extend your knees until your legs are almost straight but without locking them. This will alleviate extra pressure on the knee joints. Hold your position for a few seconds, then inhale and release the weight to return to your original posture. The whole movement from start to finish should be slow and controlled. After completing 1 set, you’ll be able to figure out if you can gradually increase your weight load for the next set. Try to do 3 sets of 8-12 repetitions. Another demanding alternative, is only using one leg at a time.
To repeat, you mustn’t underestimate the seated leg extension machine. The movement may look simple, but because it really targets the quads, you should only use a moderate weight load. It’s not a machine that’s meant to be used with a substantial amount of weight. And remember, if you have pre-existing conditions or injuries, always consult with your physician first. Your knees are very delicate joints which are supported with many ligaments and tendons. They need to be well taken care of when possible.
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