Adjustments for Knee Pain on the Leg Press

Scenario: your knee hurts when using the leg press.  Should you stop using it?

No, at least not right away.  I never advocate working through joint pain (not to be confused with muscle "burn"), but there are several confounding factors.  A simple adjustment or two can eliminate all of the joint discomfort. 

As for why you should exhaust your options to make the leg press work, it's the cornerstone of a strength training program.  The leg press utilizes the gluteus maximus, hamstrings, and quadriceps: the three largest muscles/muscle groups in the body.  As recently discussed on Health-Actualization, using the leg press can lead to increases in lower back bone density, in addition to strengthening the bones of the knee and thigh.  The strength gained from a leg press directly ties to performance of important activities such as sprinting and vertical jumping for athletes, or standing from a chair and walking up stairs for the elderly.  If you want your butt and thighs to look good, the leg press can do that, too.  To state it simply, the leg press is extremely important. 

Improper Use and Knee Pain

1. When a trainee is feeling knee pain on the leg press, the first factor I look at is use of the feet.  Is he pushing through the heels or toes?  Knee pain during the exercises often occurs when people start pushing through their toes, which is the opposite of how the leg press should be performed.  Pushing through the toes overemphasizes the calf muscles, decreases the use of the glutes, and puts a lot of force (and stress) on the joints of the feet as well as the knees.  If a simple reminder doesn't correct this problem, keep moving your feet up on the footplate, one inch at a time, until it's easy for you to push through your heels.  
2. The seat may be too close to the footplate.  The greater the bend is in your knee, the weaker the quadriceps are.  If your leg press seat is too close, not only is your knee stressed, but your lower back may be as well.  I prefer to move the seat in as close as possible before your hips slide down in the seat (if you have a large gut or a current hip pain/injury, you probably have to move the seat further back).  
3. Going back to the feet, a source of knee pain on the leg press is often inward rotation of the feet.  Inward rotation is when your toes are closer to each other than your heels are.  If your feet are turned in, your hips are improperly positioned and may hurt in addition to your knees.  Ideally, your feet should be parallel to each other (although this may not work for some people, but I'll get to that soon).  

  Your Setup is Perfect but You're Still Feeling Pain

Are you out of luck?  No.  Here are a few effective tricks for eliminating knee pain on the leg press:

• You might have your feet high enough to easily through your heels, but you still feel pain.  Try moving your feet up anyway.  As you see in the picture above, the woman has her feet so high that the toes are off the footplate.  This strategy is also effective for people with past ankle injuries as it limits ankle flexion in either direction.
• Some people are accustomed to walking with their toes pointing away from each other.  For these people, having parallel feet on the leg press might cause knee discomfort.  Pointing the toes outward may help relieve the discomfort. 
• I'm sorry that I have to include this one in (you'll see why), but your footwear could be the source of your knee pain as well.  If you wear shoes that have an elevated heel, such as high-heeled shoes, it will naturally force you to push through the toes. (Side note: you might think I'm being ridiculous for putting this in, but sadly, some clients show up to work out in high heels...I'm much, much clearer on my dress code now).  Also, shoes with rounded bottoms, such as the Sketchers Shape-ups, also naturally promote pushing through the toes (and no, they don't have magic powers for burning calories or "toning" your butt).  Avoid using any shoes that have rounded bottoms or elevated heels.  

If you have any additional tricks that have worked for you or your clients, please share via the comment section.  The leg press is too important to drop from your routine when pain could be relieved with a simple adjustment.

Is Failure Successful in Causing Injury?

 
Each set should be performed to the point of muscle fatigue but not failure, because exerting muscles to the point of failure increases the likelihood of injury or debilitating residual muscle soreness, particularly among novices.  

The statement above comes from the American College of Sports Medicine's Guidelines for Exercise Test and Prescription, the eighth edition.  The American College of Sports Medicine (ACSM) is the gold standard for certifying personal trainers and the most recognized national organization for producing physical activity guidelines.

So...is the opening statement true?

Momentary Muscular Failure and Injury

Before getting into the answer, let's clearly define what "failure" in strength training is.  The act of strength training makes the trainee stronger in the long run (starting about 48 hours after the workout), but it actually weakens muscles in in the short term.  Maybe this is stating the obvious, but a trainee is strongest on the first rep and weakest on the last rep of a set.  Momentary muscular failure, or "failure" for short, is performing an exercise until your level of strength is less than that of the weight being lifted.  In practical terms, failure occurs when you start a repetition that you can't finish, no matter how hard you try.  No amount of determination or effort will complete the rep because your muscles are no longer strong enough to move the resistance (barring a "cheat" technique, such as jerking your body to gain momentum to complete the rep...but for the sake of your joints, please don't cheat!).  

Does working to failure cause injury?  Speaking from years of personal experience and basic physics, no, I don't believe it does.  Observationally speaking, I have been training clients to failure for nearly six years and have not seen any resulting immediate injuries.  A large portion of my experience features seniors with osteoporosis and arthritis.  If anyone is susceptible to potential training injuries, it would be that population.  Also, I have been training to failure myself for most of the past 10 years and have no experienced injuries during the last reps of my sets (or during any part of my exercises, for that matter).  

However, my confidence in the safety of momentary muscular failure is mostly due to the physics aspect of it.  Injuries occur when the force placed on a tissue (joint, tendon, ligament, muscle, etc.) is greater than the force that the tissue can withstand.  Remember Newton's Second Law of Motion? 

Force = Mass x Acceleration  

To injure yourself, there must a combination of mass and acceleration that your joints can't handle.  During a set, the mass (the weight you're lifting) is always the same.  As stated before, during the exercise, your muscles become weaker and, therefore, are less capable of producing a significant acceleration.  If you are going to accelerate enough to cause injury, it has to occur at the start of the set.  Fresh muscles are more capable of accelerating and causing injury.  

The one exception to this is cheating.  If you are so determined to complete the last rep that you will break form via jerking your body in some way, then training to failure poses an injury risk for you.  Other than that, I believe it is safe for the general population. 

Final Thoughts on the ACSM Statement

The other part of ACSM's statement described training to failure as a cause of debilitating soreness in strength training novices.  This does happen, but the cases are few and far between.  From my experience, the major cases of debilitating soreness occur when new strength trainees train intensely with multiple sets per muscle on the first day (i.e. five sets of the bench press, three sets of chest flys, and four sets of dips).  Using a high volume of exercise on a specific muscle group is worst way for new trainees to start.  

For anyone who is new to strength training, I recommend performing one set per muscle group with each set performed to a mild level of muscle "burn" during the first two or three workouts.  After that, working to failure should not produce debilitating soreness and, in my opinion, should not cause injury.  Training to momentary muscular failure will allow you to use as many muscle fibers as possible, allowing for the greatest strength and muscle gain, while not posing any detriment to your joints.