The topic of squatting depth needed to be put in my blog arsenal to shed some light on the squat confusion. Some people say squat ass to grass, some people say never to squat below parallel in fear that the knee will blow out. There’s no right or wrong way to squat, there’s just optimal for a given individual. I’ve heavily summarised this to keep it sweet.
In a comprehensive review of the available research of the biomechanics of squat, (Rafael Escamilla (2001) Medicine & Science in Sports & Exercise, 33(1), 127-141), Escamilla assesses the forces and muscle activity involved in different squatting styles. The important points are:
– Moderate load is placed on the PCL (posterior cruciate ligament) during the squat, which increases as the knee flexes. The PCL force occurs after 60 degrees of knee flexion with forces from ¼ to ½ of what the PCL is capable of handling, and so the squat exercise is perfectly safe for athletes with a healthy PCL. Those recovering from PCL injury should restrict the range of movement to no greater than 60 degrees of knee flexion.
This squat places the greatest amount of stress on the PCL:
– ACL (anterior cruciate ligament) forces were generated at the top part of the squat from 0-60 degrees of knee flexion. However the ACL loads are found to be low and should be safe for ACL patients to include in their programmes. However, to stay on the safe side, by increasing the forward lean of the trunk during the squat, ACL stress can be reduced greatly due to the increased hamstring activity.
This sequence of squatting moves from 0 degrees of knee flexion (photo on the left) to 45 degrees of knee flexion (middle photo) and to past 90 degrees of knee flexion (photo on the right).
– Fast squatting (one second ascent and one second descent) produced up to 30% greater shear forces than slower speed squats (two seconds each phase). Therefore anyone who has had a ACL or PCL injury are best to squat slow and controlled.
– There is no data concerning the maximum compression force that is safe for the joint, but one can assume that if very high loads are produced on a regular basis then miniscus and cartilage injury risks will increase.
– The heavier the weight, the more compressive force on the joint, however the amount of shear force stays relatively the same.
Squatting in knee rehabilitation.
ACL injury – There is low ACL stress during the squat. Slow squatting, not training to fatigue, and leaning forward from the hips to keep the shins more vertical than in a usual squat will limit shear forces on the joint.
PCL injury – There is moderate stress on the PCL which increases with squat depth. Limit your squat to 60 degrees of flexion, which means not going to parallel (which is 90 degrees) or past parallel.
MENISCUS injury – If you’ve had a meniscus tear, avoid deep squatting and squatting with high loads.
In all squatting, make sure you keep the knees out over the toes to reduce force acting on the inside of the knee.