Sit down on the machine and adjust the bottom leg pad so that it's resting up against your lower shins. Keep your back straight and hands on the handles to your sides. This is your starting position.
Lift the weight up until your legs are almost straight and make sure not to lock them out. You should always keep tension in your legs for optimum movement efficiency. Then, lower the weight back down all the way until the machine still has tension in it. In other words, don't go all the way down as to allow the weight plates on the stack to bang into each other. Stop just short of this.
Finally, repeat the entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Keep your back straight and resting up against the back pad
Don't extended your legs completely on the downward portion of the movement; no need to lock out your knees
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or increase the weight.
This is a classic exercise for the quadriceps. It's one that anyone can do and the seated position provides for a very comfortable feeling.
One thing we would like to point out here is that this particular exercise is not the best one if your goal is to build muscle. While it certainly can help with putting on some mass onto the legs, it pales in comparison when it comes to exercises like the Barbell Squat or 45-Degree Incline Press that will pack on slabs of muscle onto your quads in no time!