The geometric curvature of the lumbar spine during restricted and unrestricted squats

A Biomechanical Review of the Squat Exercise: Implications for Clinical Practice

“…That is, squat depth should be limited to a depth in which a neutral spine can be maintained. As noted above, posterior pelvic tilt is coupled with lumbar spine flexion, 37,38 resulting in compressive and shear forces occur at the lumbar spine. 14,15,39 Osteoarthritis is the most common joint disease, 61 primarily affecting the tibiofemoral joint.…”

“…The posterior rotation of the pelvis is the result of the femur compressing into the acetabulum. 37 Given that posterior pelvic tilt is coupled with lumbar spine flexion, 37,38 compressive and shear forces occur at the lumbar spine. 14,15,39 The fact that lumbar erector spinae activity does not increase beyond 90° of knee flexion, 36 suggests that passive structures (i.e., posterior longitudinal ligament) provide the resistance to the spine flexion moment.…”

The Limitations of Anterior Knee Displacement during Different Barbell Squat Techniques: A Comprehensive Review

“…The higher torque in the hips with restricted high-bar back squats indicated a higher load on the lower back, which is why the authors argued that unrestricted high-bar back squats should be the preferred technique. Accordingly, subsequent studies found that unrestricted barbell squat variations are more suitable for stimulating the lower extremities [39], minimizing strain on the lower lumbar spine and lower back in comparison with restricted techniques [8,9], and are therefore the recommended technique to improve athletic performance based on current evidence [40].…”

“…Although not reported in the literature, the recommendation to not or only slightly push the knees over the tips of the toes seems to be a very vague statement, as disproportionately large feet in relation to the lower extremities of an individual will likely not lead to reduced shearing forces. In addition, the recommendation to limit AKD results in altered knee and hip coordination [7], with a stronger upper body inclination [2,8,9], enhanced trunk flexion in the thoracic and lumbar spine [10], and reduced squatting depth [9]. Moreover, using a moderate foot stance, which represents an outward-directed foot angle of approximately 20 • with the toes pointed laterally in combination with a shoulder-width stance [11], avoiding AKD cannot be achieved by most athletes performing different barbell squat techniques [7,9,11,12].…”

“…Individual anatomy, anthropometry, and barbell placement all contribute to the resulting movement patterns during different barbell squat techniques. Although the deliberate restriction of AKD can reduce the torque on the knees, traditional recommendations of AKD result in altered knee and hip coordination [7], with a stronger upper body inclination [2,8,9], enhanced trunk flexion in the thoracic and lumbar spine [10], and consequently, disproportionately high forces transferred towards the hip joints and lower back. Additionally, most athletes employing various barbell squat techniques cannot prevent AKD when using a moderate foot stance, which is indicated by an outward-directed foot angle of roughly 20 • , with the toes pointed laterally in conjunction with a shoulder-width stance [7,9,11,12].…”