The squat is a fundamental exercise in athletic strength and conditioning programs. However, there has been concern going back to Karl Klein’s article in the 1960’s that it may be bad for the knees. With the exception of Klein’s study, nobody has been able to show that squats are bad for the knees regardless of depth or load. The July issue of the Journal of Strength and Conditioning Research revisits this topic somewhat. In this study by Cotter et al, the authors are attempting to determine if squat depth and squat load has an impact on peak external knee flexion moment (pEKFM), which they believe to be an indicator of being at risk for developing patellofemoral pain syndrome.
To do this, the authors studied three loads (unloaded, 50% 1-RM, and 85% 1-RM) for each of three depths (above parallel, parallel, and below parallel). The subjects initially performed a 1-RM at each depth and then on a subsequent session did the study at different depths and loads.
In terms of results:
• Subjects could squat approximately 147% of bodyweight at the below parallel depth, about 153% of bodyweight at parallel, and about 177% of bodyweight at the above parallel depth.
• All three depths had a similar pEKFM in the unloaded condition. But, as the loads increased the deeper the subject squatted the greater the pEKFM (so below parallel > parallel > above parallel).
• For all depths, as the loads increased the pEKFM increased (so 50%>unloaded and 85%>50%).
So the results suggest that as the weight increases, so does the pEKFM. Also as the squatting depth increases, so does the pEKFM. What does this mean? First, it may provide some guidance for individuals suffering from patellofemoral pain syndrome in terms of their squatting depth (i.e. maybe they should squat higher). Second, according to the authors it may indicate a need for a progression when approaching the squat especially for untrained or older individuals (begin with unloaded higher squats, progress to unloaded deeper squats, then gradually add weight).
Having said that, a few cautions need to be brought up. It’s unclear that pEKFM equals patellofemoral pain syndrome. It’s unclear if there’s even a relationship between the two. This study makes no attempt to establish a link between the two and is merely reporting that one measurement is increasing as load and depth does. In other words, it’s not saying that deep heavy squats = degenerative knee pain. The only way to do that is to either put subjects on different squat programs and see who develops pain or to study populations of squatters.
Subjects tested their 1-RM on all three depths during the same session. In the study they first tested their 1-RM on the below parallel squats, then the parallel squats, then the above parallel squats. Cumulative fatigue could have an impact on the results of the parallel squats and the above parallel squats.
The results of the 1-RM testing don’t seem to indicate very experienced squatters. Now, this may be impacted by the shear amount of 1-RM testing performed in that session, but even with the first 1-RM test (below parallel, conducted before fatigue set in) a 200% bodyweight squat would be considered respectable in an athlete. This means that the results may be impacted by poor technique, poor strength, or a lack of muscular development and must be applied to trained athletes with caution.
It’s always interesting to see how the body experiences exercise. Sometimes though we go overboard and assign too much importance to a lab measure
Cotter, J.A., Chaudhari, A.M., Jamison, S.T., and Devor, S.T. (2013). Knee joint kinetics in relation to commonly prescribed squat loads and depths. Journal of Strength and Conditioning Research, 27(7): 1765-1774.
