The leg extension machine is a good piece of strength equipment, isolating the quadriceps muscles in the front thigh. These are key muscles for lower body stability, balance and power generation. Sitting elongates the quads and over time weakens them!
Because most leg extension machines have one pad for both legs a progression to single leg extensions would be prudent. As many of us have a "stronger side," performing the leg extension with both legs may result in the stronger leg taking over the exercise (one of the drawbacks of selectorized machines). Isolating each leg with single leg extensions will ensure that each side is pushing the weight and will also provide feedback as to whether or not you have a "weaker side." You'll feel the difference as soon as you lift the weight with each leg. Body symmetry should always be a key focus with exercise training and a good trainer should help you identify and correct the muscle deficiencies you have. , , and believe me, everybody's got deficiencies.
I've also offered an isolation of the vastus medialis oblique (VMO), which is the main stabilizing muscle for the knee itself. A good one to do to keep the knees well supported.
Our Exercise of the Month demonstrates these three different exercises you can do on the leg extension machine.
#Leg Extension Exercise