How to Prevent Knee Problems for Leg Presses

The motion on a leg-press machine works the same muscle groups as a squat, only instead of squatting down, you're pressing up. The leg-press machine can give you more control than with a squat, which is great if you already have bad knees. But like all exercise machines, they can be dangerous if used improperly. Good form and common sense can work together to make the leg press a valuable and safe part of your regular leg workout.

Warm up before you start using the leg press machine. Walk on the treadmill for five minutes and stretch your major muscle groups, focusing on the knees,before using a leg press machine. Try this stretch: stand near a wall for support and bend your knee, bringing your foot to meet your butt. Reach behind you and grasp your foot to deepen the stretch and hold for five seconds before releasing and repeating on the other side. The American Academy of Orthopedic Surgeons notes that a proper warm up increases muscle temperature and blood flow to increase your performance.

Press only as much weight as you can handle. In general, you should be able to do at least 8 presses, but no more than 12 for the ideal weight. If you can't get to 8 repetitions, you're pressing too much. Remove some of the weight and try again for a safer experience.

Start with your legs at a 90 degree angle -- nothing less. Bending your knees too much can cause excess strain. Press with a smooth, continuous motion to protect your knees. You should never be thrusting or using jerky motions with a leg press machine.

Press upward until your legs are almost straight, but never lock your knees. Locking your knees causes strain and can even result in hyper-extension and injury. Always keep your knees soft. Push through your heels not your toes, much like you would with a standing squat. Pressing through your heels ensures that your thighs (quads) bear the brunt of the exercise. Your quads are the muscles that power this exercise, and they're the ones that should get tired, not your knees.

Slowly bend your knees and bring the foot plate back to the 90-degree angle starting position. Repeat the exercise 8 to 12 times.

Tips

Enlist the help of a spotter to check your form and help you maintain proper technique. A spotter can assist you in case you unintentionally lock your knees or have trouble lifting the weight. They make sure that a minor issue doesn't become a big injury.