Originally Posted by BendtheBar
A few quotes from McGill that might help the discussion:
“There are only so many bends or a ‘fatigue life’,” in your spinal disks,” says Stuart M. McGill, a professor of spine biomechanics at the University of Waterloo. Inside each disk is a mucus-like nucleus, he says, and “if you keep flexing your spine and bending the disk over and over again, that nucleus slowly breaches the layers and causes a disk bulge, or a disk herniation.” A herniated disk won’t show through your swimsuit, but it’s no fun, and can cause persistent back and leg pain, weakness, and tingling.
Think of the oft-repeated advice for movers: bend at the hips and lift with your legs, not your back. And what is a sit-up but a back bend done in a lying position? “When people are doing curl up over gym balls and sit-ups, and this kind of thing, they are replicating a very potent injury mechanism on their back,” says McGill. “Every time they bend it they are one repetition closer to damaging the disk.”
The only sit up specific quote I could find was this:
LOL, yeah, I read that rubbish
as well; why do I consider it rubbish? Well, for one, the average lifespan he allocates to the discs (he does give an exact number but of the top of my head I cannot remember it) is less than most of us have already bent them in that poor manner anyway and we should all have extremely bad backs by now. With all the sit-ups, all the poor school gym sessions and every other exercise along with just daily living, we should all have gone way over the threshold or lifespan that he allocates for the spinal discs, yet we're still here some 40+ years on and lifting strong.
Bob People's knew a thing or two and he deadlifted with a flexed spine at times, some of the older articles even suggest a rmedy for a bad back is lifting with a flexed spine in order to heal and strengthen it.
Back to the original point though, if you take the number of times the spine should flex prior to being rendered useless by McGill, and compare with the figure you get from: multiplying the number of days you've been on this earth, then multiply that figure by 10 (representing a measly 10 sit-ups for every day of your life) even that outweighs the amount that of good health a person has to look forward to from their back...and you may only even manage to get to days x 1 which means getting out of bed once and then not flexing your spine for the rest of the day for all those days you've been alive...yep, it doesn't add up, quite literally.