The barbell back squat and forward displacement of the knees;

The barbell back squat and forward displacement of the knees;

The barbell back squat is one of the most commonly prescribed, versatile exercises amidst Health and Fitness Professionals, worldwide. Benefits of this specific lift, and training through its range of motion could arguably carry-over to every single sport or physical activity known to humankind… However, for such vastly-utilised training technique, there lies falsity and confusion in a number of areas regarding “proper” form in perfection of the orthodox barbell.

This brief abstract looks at evidence for optimal verticality of the shank of the tibia and fibula in relation to the ankle during the full eccentric and concentric components of a barbell back squat repetition; with respect to a commonly preached idea that:

“One constituent to proper form of the barbell back squat is achieved only if the knees do not travel anterior to an imaginary point immediately perpendicular to the respective limb’s toes”

A 2003 study examined joint kinetics occurring when forward displacement of the knees is restricted vs. when such movement is not restricted. 7 weight-trained males performed 2 variations of barbell back squats; either both knees were permitted to move anteriorly past the toes (unrestricted) or a barrier prevented the knees from moving anteriorly past the toes (restricted). Differences between static knee and hip torques for both types of squat (unrestricted or restricted barbell back squats) were compared. Torque results were reported (N.m; mean +/- SD) as follows:

·      Unrestricted squat:

o   Knee torque = 150.1 +/- 50.8

o   Hip torque = 28.2 +/- 65.0

·      Restricted squat:

o   Knee torque = 117.3 +/- 34.2

o   Hip torque = 302.7 +/- 71.2.

Furthermore, the barrier-restricted squats also produced more anterior lean of the trunk and tibio-fibular shank, as well as a greater internal angle at the knees and ankles… undesirable.

Clearly, these data show that, what might seem like small tweaks to the barbell back squat technique, can majorly affect the distribution of forces between the knees and hips. Noted kinematic differences at the trunk can also result from these small changes.

What do these data mean practically? Well, although anterior translation at the knees during the movement might minimize stress locally - on the knees themselves - it is important to recognise the barbell back squat as a compound exercise, and therefore the joints to prevent over-loading with stress are not just the knees, but are multifarious.

This evidence suggests that is highly likely that forces are inappropriately transferred to the hips and low-back region when attempting to restrict the knees to a position behind the respective toes, during the entirety of a repetition.

Thus, the commonly proposed idea that “good form” in the barbell back squat exercise entails restriction of all parts of the tibio-fibular shank posterior to the foot, might be less than optimal, and in fact a facilitator to load injury at the hip/trunk. Appropriate joint loading during the barbell back squat may require the knees to move slightly past the toes.

Jack Morris

Sports Scientist/Physiotherapist