I came across an interview with Dr. Stuart McGill some time ago & he was answering a question pertaing to heavy deadlifting & flexed spine lifting He had the following to say:
A flexed spine uses less hip strength but increases the hydraulic pressure on the posterior part of the disc. This increases collagen delamination and the risk of a bulging disc. So if a person lifts with a flexed spine, what they do for the rest of the day matters even more. For example, incorporating full motion crunches for this heavy lifting athlete would be a mistake.
The concept of cumulative loading would need greater consideration. In other words, lifting with a neutral spine increases the tolerable training volume. That alone is a real gift to many lifters and particularly athletes who use the deadlift as part of a larger training program.
He goes on to talk about "collagen delamination":
Disc collagen delaminates mostly from motion, but this weakening is accelerated under higher loads. Specifically, the fibers split apart allowing the nucleus to flow through. Therefore, locking the spine so no motion occurs until the end of the lockout is helpful. But this distinction only holds true with no prior cumulative delamination.
Usually there will come a point when accumulated delamination, or a further weakening of the disc, will allow the nucleus to travel through the annulus. Then the person will experience "flexion motion with load intolerance." Once this stage happens, deadlifting will cause debilitating pain.
Now for a paradox: If a guy has a long history of lifting with some flexion, the trabecular bone in the vertebral body will be strongly adapted. It appears as though stronger and denser trabecular bone reduces vertebral end plate damage and the ensuing delamination process. This characterizes the grand old men of powerlifting who have survived years of lifting with a flexed spine.
But a newer lifter has a higher risk since they don't have years of loading history to create the adaptation. But the loading is needed to stimulate the adaptation, and this is the most perilous time. Some will survive, but others will have the legacy of a problematic back.
The lifting with the neutral spine increasing tolerable volume kinda makes sense. As far as I understand this, most of our lifts (warm-up to acclimation) should be with decent to good form, certainly with a neutral spine. However, on the Heavier, near maximal & maximal attempts a little to quite a bit of rounding can occur & THATS fine since it constitutes a small portion of the overall training volume. I suppose there is a certain amount of extra risk involved & each one has to decide how far they are going to go, but its not a black & white situation of either being injured or un-injured.
Now, for the technical stuff, I wasn't able to grasp the delamination part. : (
AS for the trabecular bone (or Cancellous bone) is actually a type of spongy bone. It typically occurs at the ends of long bones, proximal to joints and within the interior of vertebrae. Now as far I know, all bone structure has the capacity to adapts to the load placed on it, however what I think gives the trabecular bone an advantage is that it is highly vascular so that should help it adapt at least faster (I think?). He then proceeds to say that stronger (intervertabral) trabecualr bone reduces vertabral end plate damage & delamination. Now as far I managed to figure this out vertabral end plates undergo damage AND remodelling (healing/adaptation) on their own just fine (as do all bones in the human body) so it would adapt to the heavier loads TOGETHER with the trabecular bone. At least, thats what I managed to figure out, still no idea on delamination.
So does it make sense or not? what do you guys think?
Shhh….my common sense is tingling.