Deadlifting, Bending etc With a Flexed Spine is Dangerous

Despite what “influencers” may post on a daily basis this has been studied repeatedly and is NOT debatable!!!!! There is a HUGE DIFFERENCE in SHEAR FORCES IN THE SPINE!!

Shown in picture 1 is a neutral lordotic posture where more musculature is active and being used to support the moment , the SHEAR force is reduced too 200 N
In picture 2 you see a fully flexed spine Where the spinal erectors shut off and the posterior tissues are strained . The SHEAR forces are at 1900 N. That is a Drastic difference!!!
Picture 3 is a Lateral View of standing neutral posture -any deviation of this posture with improper movement is going to place harmful stresses on the spine .
“ Low Back Disorders” Dr Stuart McGill
“Basic Biomechanics of the Musculoskeletal system “ Margareta Nordin & Victor H.Frankel

Repeated Spine Flexion and Bending Clinical Relevance

Although much ergonomic effort has been devoted to reducing spine loads, it is becoming clear that repeated spine flexion-even in the absence of moderate load-will lead to discogenic disorders. Furthermore, evidence shows that the direction of the bending determines the location of the annulus damage (Aultman, Scannell, and McGill, 2005). Ergonomic guidelines will be more effective once factors for flexion repetition and direction are included.