What I mean is that no pressure is added in the body axis direction - which is the direction that loads the disks in the spine - by pressing when the legs are perpendicular to that axis, which is the case in that leg press machine. Of course, if the back rest is not horizontal there is some pressure due to gravity, but it is not affected by the extra weight or machine resistance (and it is actually less than the pressure while sitting, due to the incline of the back rest).
I would need to look into this more but, I find it very difficult to believe that when wedging your spine between shoulder pads and a loaded plat form, the load of the platform doesn't influence the stress on the spine. However, in my mind it's not relevant since, I "like" stress on the spine and body. I don't like poor application of stress, but I think stressing the body is essential.
Mr. DeSimone claims that by applying a lot of pressure for many years you (probably?) harm your disks. Maybe by using a perfect technique the damage can be minimized or even eliminated (I have no idea. Personally I never consider what will happen to me if I apply a perfect technique for the same reason I don't give much thought to how I will spend the money I'm gonna win in the lottery) but his point is that with heavy squats your spine is bent a little inevitably, so more pressure is applied to one side of the disks than the other, and doing it over and over again for years will eventually harm them. As I said I'm just a layman, so I can only say that the argument sounds reasonable to me. While muscles, bones and tendons will get stronger with use, it's not the case with the disks which are made of cartilage. I would suggest they are more like your teeth; lifting heavy weights is the equivalent of crushing nuts by chewing them.
If you don't aspire to use perfect technique, then without sounding like an a$$hole, it's no wonder the argument is holding water, to be honest. This is analogous to me taking the leg press recommendation on board, going into a a deep leg press and allowing lumbar flexion and chewing up the lower back anyway (i.e doing it wrong). I know the recommendation was to avoid this when leg pressing, just like my recommendation is to squat properly and not incorrectly.
Your body just degenerates, it's part of the aging process. Just living for years and years will cause wear and tear and eventual harm if you're not gone before that sets in. It's a brutal fact that we struggle to deal with but it's one of the surest things in life. Just like a car eventually clocks up enough miles that it needs scrapped, our bodies do the same. Driving like an idiot shortens the life span of your car. Driving for sport also does this (which is akin to powerlifting or, any sport, and sport in essence is "over use"). However, not driving your car is a great way to seize up the breaks, wheels, allow air to leak from the tyres, flatten the battery, etc My brothers car has been sitting in my drive way doing next to nothing for about 2 years. It's a shadow of it's former self. Even the doors have seized up. I'm taking the analogy too far. My point is for optimal health you need the right amount of activity, not too little, not too extreme. You need a middle ground. Don't throw out the baby with the bath water and go to the other end of the spectrum. There is also no reason that people training for "general" strength end up as beat up as powerlifters. If this is the case then I guarantee there will be faults in both your programming and your technique.
OTOH I guess it may be argued that by strengthening the back muscles you get better stabilization of the spine so maybe there is less wear and tear on the disks throughout the day and maybe it compensates for the extra pressure while squatting.
To be honest I think this is half of the problem I have with logic. Too much focus on muscles, not enough focus on movement. The majority of people I see with back pain already have strong lower backs and this is largely why they are in pain. Their lower back takes over in just about every movement you can think of, from squatting, hinging/deadlifting, lunging, stepping, to even reaching their hands over head. Most untrained people can't do a plank without turning it into a lower back exercise. They spend most of their time sitting down compressing the lower back, then whenever they stand they spend the whole time hanging off the lower back (forward weight shift, anterior pelvic tilt, forward head posture). Most of the time the lower back needs a break and a key factor in giving the lower back a break is RE learning proper hip function, and how to load the hips vs the spine. To be honest quad dominant exercises only enforce the movement issues which are at the route of the problem. I spend most of my time with new clients keeping the quads OUT of exercises. I rarely see the need with new clients to add quad specific work, unless they want bigger quads, which is normally more of a concern than a desire (especially with women).
But the claim is that by squatting heavily you will also be more prone to "back injury" next time you lift your sock. BTW, it happened to me once and put me in bed for a week.
My claim is that if you have dysfunctional movement patterns, you are more prone to a back injury whether you squat heavy or not. Of course, piling loads of weight into an already dysfunctional pattern is just reckless. There is also an argument that a leg press plays to the dysfunction, too. However, if you have that dysfunction, you're prone to it regardless. It's just a matter of time. Movement doesn't seem to be taken into account.
Well, Mr. Desimone makes the case that mother nature did not intend us to carry heavy weights on our shoulders - that's the point of the pyramid analogy he made.
We were intended to squat, though, and we were also designed to "adapt". And pyramids don't move, minus any illegal substances that may be available.
While this is encouraging, the issue is more about accumulated damage for the long run rather than injuries while training. Still, a good point.
Yes, it is accumulated damage, not doubt about that. But, how am I able to take people who have accumulated enough stress to cause damage and pain, and get them back to moving well and lifting heavy things with no pain whatsoever? And i'm just a rookie.....
The things I think are getting repeatedly overlooked are movement quality, lifting technique, and the relevance of "damage" anyway...
This is the study showing people without back pain having bulges and protrusions - http://www.nejm.org/doi/full/10.1056/NE ... 7143310201
Only 36 percent of the subjects had normal disks. This is isn't the only study that's found this. It's safe to assume that if you train 10 people, most of them have "damage" to their spine, regardless of whether they have pain or not. It also stated that the prevalence of disk abnormalities had little significance to physical activity. As you would assume, the older, the more likely there is to be damage. So if you have 10 clients who are 20 years old, it might not be too bad. If you have 10 who are over 40, then you need to assume that most of them have underlying "damage".
So, if I can be completely pain free yet have this damage, what exactly causes me to be in pain?
This isn't necessarily known yet but, what is gaining momentum is - How do they move?
If you take someone that moves like crap and load them up on heavy back squats then you are just begging for injury. If you take someone that moves well and clears the necessary criteria to make heavy back squats an option for them, then you will most likely have no issues at all. Of course you need to define "heavy", though. Just blaming back squats is what i'm disagreeing with. There are too many other things to consider. I'm also disagreeing with the solution. Training on machines does nothing for your movement, if anything this can make movement worse, although like lifting programs, the devils in the details in this respect, too.
I wish I could have this kind of discussion with the trainers in my gym... On second thought, in that case I would probably spend the whole training time discussing the issues which I much prefer over sweating, any day of the week :-) Oh, well.
I talk far too much lol, especially when asked about pain, technique, movement, or strength. Can't help myself most of the time, it's something i'm very passionate about.