Stress for Vertebral Bodies and Intervertebral Discs with Respect to Squatting Depth

Abstract

For the development of speed strength in professional sports, "specific" strength training in the half or the quarter squat have been recommended. Due to the better lever ratios, higher loads have to be used to induce the necessary training stimuli compared to the deep squat. Therefore, intradiscal pressure and compressive forces on vertebral bodies increase. Calculated compressive forces for the L3/L4 vertebral segment were revealed to be 6-10-fold bodyweight when the half or the quarter squat was performed with 0.8-1.6-fold bodyweight. After 10 weeks of training, physical education students have even been able to lift 3.89-fold bodyweight in the one repetition maximum (1-RM) of the quarter squat. The presented dependence of squatting depth, load and their influence on the spinal column have not been discussed before. A search for relevant scientific literature was conducted using PubMed. Concerns about increased risk of injuries in the deep squat have been disproven by plenty of cross-sectional studies with professional athletes. On the contrary, the comparably supramaximal weight loads in the half and the quarter squat should be regarded as increasing injury risks caused by the higher shear and compressive forces in the vertebral column. Therefore, we come to the conclusion that the half and the quarter squat should not further be recommended.

Lumbar Loads and Muscle Activity During Flywheel and Barbell Leg Exercises

“…Lumbar vertebral compressive strength has been studied in cadaveric experiments, wherein a rather wide range of average compressive forces, between 4 and 14 kN, has been reported to cause failure. The anterior shear strength of lumbar vertebrae has been reported to range from 0.6 to 3.2 kN, with average values of 1.7 and 1.9 kN for women and men, respectively (for reviews see Gallagher and Marras (18), Hartmann et al (24), and Jäger (28)). Notably, in several of the studies reviewed in the aforementioned articles, the cadaveric specimens were obtained from a wide range of individuals, spanning ages 10–90 years and representing varying physical fitness levels (24,28).…”

“…This balance can be difficult to obtain and manage. Guiding data for athletes and for astronauts are limited and rely on existing biomechanical studies of heavy resistance training (9,24,26).…”

Kinetics and Kinematics of the Squat and Step-up in Well-Trained Rugby Players

“…For example, decreasing the stability of an exercise can result in increased balance requirements, antagonist recruitment and co-contraction, and trunk/hip activation levels (9, 22,474). Additionally, unilateral exercises require a lower total external load which would be valuable in unloading anatomical structures such as the spine (263,421). However, the increased requirement for stability has been shown to decrease the force output of agonists and when combined with the lower external resistance possible, suggests that unilateral exercises are perhaps less effective for the development of maximal strength (376,386).…”

Higher Risk of Intervertebral Disc Herniation among Neurosurgeons Than Neurologists: 15 Year-Follow-Up of a Physician Cohort

“…It is commonly accepted that older age, obesity, and high physical activity are risk factors of spinal disc protrusion [ 13 , 14 , 15 ]. There are also a few reports addressing certain jobs and activities, including football and heavy lifting, that may predispose subjects to such problems [ 3 , 4 , 9 , 15 , 16 , 17 ]. The mechanism of spinal disc herniation is generally correlated with an excessive load over the vertebral segment and deficiency of structural strength, for instance, a torn annulus fibrosis.…”