Fitness industry professionals are used to lively debates. We are used to hearing researchers argue dynamics vs. static stretch. We’ve heard a lot of opinions about the best ways to build muscle: light weight, high reps or heavy weight, low reps. And the debates continue. One of those controversies involves the use of particular weight-lifting machines common to many gyms. Are these machines a good use of your time and energy? Can some of these machines really be bad for your health and fitness?
Leg extension machines are a controversial weight machine. These machines have a padded seat and bar that rest at the junction of the leg and foot. As you lean back in the seat, raise your legs until they are almost straight, then slowly lower your legs. The amount of weight lifted by the legs can be adjusted.
If you use this type of machine, you are focusing your lifting efforts on the quadriceps (the large muscles in the front of the thigh), that is, the vastus medialis, vastus lateralis, vastus intermedius, and rectus femoris. Interestingly, this machine allows the hamstrings to fully relax while the quadriceps do all the work. Many avid lifters are drawn to this particular machine because they feel that this isolation really helps them emphasize each of the four quadriceps muscles. And of course, if you’re being judged on your physique while posing, you’ll want more muscle definition. They’re right about this isolation, but are leg extension machines a good weightlifting option for the average person?
I do not think so. Of course, as you would expect with any controversy or debate, there are various schools of thought regarding leg extensions. Some say that these machines are hard on their knees. Others say that the machine has a common rehabilitation method for knee injuries or knee surgery: the leg extension machine. How can both be true? I would suggest that the use of leg extensions in a rehab setting works because light weight is used to correct muscle imbalances. But if we’re talking about the typical person who does leg extensions on the machine at my gym, he’s not lifting 5 or 10 pounds. Rather, they are lifting a lot more weight. Such a difference in weight makes a world of difference in terms of how the knee is affected.
Other common criticisms of the leg extension machine:
The leg extension machine can cause a condition known as chondrolmalcia patellae. This painful condition causes the smooth and normally fluid arc of motion of the patella to become twisted and misaligns the patella.
A 1988 study found that ACL strain occurred when lifters fully extended their legs during the leg extension exercise. This tension could finally cause a tear. Tears often require surgery.
A lot of people have muscle imbalances because they are unbalanced in terms of hamstrings vs. quadriceps strength. This muscular imbalance can lead to a number of knee problems.
But you might be thinking, “What can I do instead of the leg extension machine?” Squats, when done correctly, are the absolute best leg-strengthening exercise. Squats are the king of leg exercises. Don’t opt for isolation while ignoring other muscles. Squats are also a functional exercise. This means that they mimic the natural movements that people use throughout their everyday lives.
Use your time at the gym wisely. Work all those leg muscles at once by doing squats. Leave leg extension machines to professional bodybuilders.
