Deadlifts & Back Flexion

Why is rounding of the back during a heavy deadlift such a bad thing? Power is force (or load) times velocity (how much and quickly someone moves their spine). A gymnast has relatively low power at the spine as they move their back quickly but under low load. A powerlifter on the other hand who locks their spine and moves about the hips, generates high force but low velocity at the spine – therefore power stays low.

When power is low, injury risk is low (this is based on the teachings & research from Dr. Stuart McGill 
If you want to keep your injury risk low, work to lock your spine and move about the hips, not your back.

Want to read some of the research on this topic? Start with these articles:
1)Wade KR, Robertson PA, Thambyah A, Broom ND. How healthy discs herniate: a biomechanical and microstructural study investigating the combined effects of compression rate and flexion. Spine. 2017;39(13):1018-28
2)Callaghan JP & McGill SM. Intervertebral disc herniation: studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clin Biomech. 2001;16(1): 28-37
3)Claudio T, Drake JD, Callaghan JP, McGill SM. Progressive disc herniation: an investigation of the mechanism using radiologic, histochemical, and microscopic dissection techniques on a porcine model. Spine. 2007;32(35):2869-74
4)Spencer K & Croiss M. The effect of increased loading on powerlifting movement form during the squat and deadlift. J Hum Sport Exerc. 2015;10(3):764-774
5)Cholewicki J & McGill SM. Lumbar posterior ligament involvement during extremely heavy lifts estimated from fluoroscopic measurements. J Biomech. 1992;25(2):17-28

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