Professionals in the fitness industry are used to a lively debate. We are used to hearing researchers argue dynamics vs. static stretch. We’ve heard many opinions about the best ways to build muscle: low weight, high reps, or high weight, low reps. And the debates continue. One such controversy 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 be harmful to 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 and then slowly lower them. The amount of weight that the legs lift can be adjusted.
Using this type of machine will focus your lifting efforts on the quadriceps (the large muscles in the front area of the thigh), namely the vastus medialis, vastus lateralis, vastus medialis, and rectus femoris. Interestingly, this machine allows the hamstrings to fully relax while the quads 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 are judged on your physique while posing, you will want more muscle definition. They are 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 several schools of thought regarding leg extensions. Some say these machines are hard on the knees. Others say that the machine has a common rehabilitation method for knee injuries or knee surgery which is the leg extension machine. How can both be true? I would suggest that using 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 doing leg extensions on my gym machine, they’re not lifting 5 or 10 pounds. Rather, they are lifting a lot more weight. This difference in weight makes a huge 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 kneecap to twist and misalign it.
A 1988 study found that stress on the anterior cruciate ligament occurred when lifters fully extended their legs during the leg extension exercise. This tension could eventually cause a tear. Tears often require surgery.
Many people have muscle imbalances because they are unbalanced in terms of hamstring vs. quadriceps strength. This muscle 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 best exercise for strengthening your legs. Squats are the king of leg exercises. Don’t go 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 daily lives.
Use your time in the gym wisely. Work all your leg muscles at the same time by doing squats. Leave the leg extension machines to the professional bodybuilders.