Are Deep Squats Really Harmful?

You often hear from self-proclaimed experts that squats with an angle of less than 90 degrees between your shins and thighs are harmful. Is that really true?

As early as 1961, the first papers on the theory of "deep squats" were written (e.g. "The deep squats exercise as utilized in weight training for athletes and its effects on the ligaments of the knee"). In this paper, Dr Klein argued that squats loosen the knee ligaments (particularly the collateral and cruciate ligaments). Weightlifters were compared with a control group.

Hard to believe, but toddlers, and people in many cultures around the world, often sit in a deep squat. This way of sitting can still be observed frequently in many African countries.

With shallow squats, the ligaments are exposed to greater loads, and the force acting on the ligaments decreases once the 90-degree angle is exceeded. (e.g. M. Sakane & colleagues, 1997; G. Li & colleagues 1999 and 2004; A. Kanamori & colleagues, 2000; K.L. Markolf & colleagues, 1996).

A 2001 study by R.F. Escamilla & colleagues found that weightlifters (who each performed deep squats with heavy weights) have stronger knee ligaments than the control group.

Now let's turn to flexibility in the knee and hip joint. Flexibility is essential for preventing injuries. If limited flexibility means the squat can't be performed below a certain angle, there's a risk of serious injury. Let's say a footballer only ever squats down to a joint angle of about 100 degrees in his strength training. If he then has to make a lunge in a game situation that brings his joint below the 100-degree angle, the risk of injury will be very high, because he'll produce less force at that angle than if he had always squatted through the full range of knee-joint motion.

This is due to the effect of regulating the number of sarcomeres in series, through the adjustment of the optimal sarcomere length at which the muscle can produce its maximum force. As already mentioned, if a muscle is trained through a shortened range of motion, the number of sarcomeres decreases. The remaining sarcomeres are then set to a length that offers optimal conditions for developing maximum strength in this now-shortened state (Williams and Goldspink 1978).

As a result, for a given muscle length, the average sarcomere length is shorter. In humans, training through the full range of motion shifts the optimal joint angle for producing maximum torque. The knee angle at which maximum torque can be generated therefore shifts as well (Toigo 2006).

In other words, after training, maximum torque is produced at a greater muscle length (in the case of squats, that means a deeper squat), assuming the muscles involved have become longer. During sporting or everyday activity, a muscle can then always be loaded through a shorter range of motion.

After an injury, you should start your exercises by increasing joint flexibility. This is also why most physiotherapists recommend shallow squats to patients who are recovering from an injury.

That people who regularly do deep squats have stronger ligaments has been confirmed in several studies. That's actually logical: if deep squats really led to weak ligaments, weightlifters, for example, would fail in their sport (which is obviously not the case).Conclusion

The idea that squats should only go down to 90 degrees of flexion has purely traditional roots and is therefore wrong. The smaller the angle, the larger the knee-joint surface over which the force can be transferred. As long as the person training has no orthopaedic issues (e.g. back or knee problems) and performs the exercise with correct form, they can do squats through the full range of angles.

So go on: ASS TO THE GRASS!