One of the challenges in the fitness community is dispelling the numerous myths that have persisted over many years. “Squats are bad for your knees.” “Deadlifts can damage the lower back.” And one that may never go away: “Aerobic training is the fastest way to lose fat.” Let’s tackle this one: “The knees shouldn’t travel past the toes during squats and lunges."
Although it’s difficult to determine exactly where this myth originated, consider that there have been numerous studies that have looked at the forces on the knee during the squat. On the surface, there is cause for concern.
One study that is frequently cited by fitness professionals was conducted by researchers at Duke University that was published in 1978 in Research Quarterly. Tom McLaughlin, a sports scientist who has done extensive studies on the biomechanics of powerlifting, was the lead researcher in this study. McLaughlin and his colleagues discovered that the knees experienced less shearing forces during the squat when the shin was held in a more vertical position. Another study, this one conducted by the University of Memphis and published in 2003 in the Journal of Strength and Conditioning Research, found that allowing the knees to extend over the toes during squats significantly increased stress on the knees.
While research studies are enough to convince many aerobic instructors, personal trainers and strength coaches to modify their lunging and squatting technique, you must also consider empirical (real world) data.
First, squatting with the knees beyond the toes is a normal sitting practice in some cultures. Said the late Dr. Mel Siff in his book, Facts and Fallacies of Fitness, “Many aboriginal folk squat many times a day while carrying out their daily chores, while the Japanese sit on the floor with their knees folded fully flexed beneath them bearing all their bodyweight for prolonged periods daily without producing an epidemic of knee injuries.”
Siff adds that in sports such as fencing and wrestling, the knees project far in front of the toes “without being identified as a major cause of injury.” And if we’re going to start condemning sports, perhaps we should start with bicycling because you can’t pedal without the knees moving in front of the toes. Cross off sprinting too, as the start position of these events involves having the knees extended well in front of the toes.
Continuing with this theme, the recommendation to not perform lunges or split squats without the knees going in front of the toes is impossible. Yes, you can restrict the amount the front leg goes forward -- and perhaps this is one reason why aerobic instructors often promote reverse lunges (where you step back) to ensure that the knee stays behind the toes? But the question to ask is, “What about the back leg?” The start position of the split squat is the with back knee in front of the back foot, and the movement forward in a lunge immediately causes the rear knee to travel in front of the rear foot.
We can take this matter to another extreme with weightlifting. In the sport of weightlifting where athletes compete in the snatch and the clean and jerk, athletes catch the bar in the snatch and the clean with the knees well in front of the toes. Not only do these athletes’ knees extend over the toes, but they perform these lifts with heavy loads and bounce out of the bottom! Despite these taboos, a study conducted in the United Kingdom found that the lowest injury rate was in the sport of competitive weightlifting.
How about long-term damage to the knees? To address this issue, consider that a paper published in Sports Medicine in 2013 looked at the risk of injury and degenerative conditions from performing deep squats (which force the knees to extend over the toes). The researchers concluded, “Concerns about degenerative changes of the tendofemoral complex and the apparent higher risk for chondromalacia, osteoarthritis, and osteochondritis in deep squats are unfounded.” What is also interesting is that the researchers found that the highest stresses on the knee occurred at 90 degrees, not in the deep squat position.
Getting back to the 2003 University of Memphis study, researchers found that restricting the motion of the knees during the squat (by placing a barrier in front of the knees) dramatically increased the torque on the hip. While this type of squat (which resembles more of a good morning exercise) may enable powerlifters to lift more weight, the change in stress may subject the powerlifter to a greater risk of developing hip and spine injuries.
Squats and lunges with knees over toes? Consider this myth busted!