All strength exercises come with a risk of injury. Your muscles are required to lift amounts that are heavier than normal, so there is a risk of pulling or straining a muscle or injuring a joint. The leg press is no exception. However, when used properly, the leg press is safe for your knees and may help prevent knee injuries.
Before your first workout at a gym, you have to sign a waiver that states you are participating in an activity that may result in an injury. You see this disclaimer at the beginning of workout videos and books. Weight machines and other strength training equipment does have a risk for injury. However, this risk is less than the risk associated with playing sports such as basketball and football. This is because the leg press is controlled, moves through one range of motion and is not a stop/start activity.
You can help protect the safety of your knees by doing a proper warm-up before using the leg press machine. Spend five to 10 minutes doing full-body movements, such as walking, cycling or jumping rope to warm your legs. Your knees are also protected when you select the right amount of weight. Use a weight you can press for one to three sets of eight to 12 repetitions. If you are unable to do eight repetitions, decrease the amount of weight. Protect your knees by using the leg press through a full range of motion and by keeping your heels on the sled. Your knees should be facing the same direction as your toes.
The leg press machine is considered a closed-chain exercise. Closed-chain exercises use more than one muscle group and are often labeled as functional exercises. In the case of the leg press, the closed-chain exercise refers to your knee joint remaining stable and in one place, compared with a leg extension in which your knee joint has much more movement. The safety for your knees during the leg press is increased because your quadriceps and hamstrings both contract to stabilize the ligaments surrounding your knees.
Weight training exercises are also beneficial for injury prevention. The American College of Sports Medicine reports three injury-reduction benefits of resistance training with equipment such as the leg press. You improve the density of your bones which reduces stress fractures to the knees. You strengthen the ligaments and tendons surrounding the knees for greater support and stability. You also equally strengthen the muscles that surround the knees to keep the joints in healthy alignment.
Your Body Type
If you have a preexisting knee condition, check with your doctor before using the leg press machine. If you experience any discomfort while using the machine, stop the exercise and adjust your form. If you still feel pain or discomfort, check with a fitness trainer for proper technique. Not all machines fit all body types, so it may be a matter of switching to a different brand of leg press machine.