Why is lifting items “with your back” dangerous? Why can’t back muscles be strengthened?
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Your spine is a part of your central nervous system, which helps with sensation and motion. There is a risk of damaging the spine when lifting with your back versus with your legs.
You can strengthen them for sure but the amount you can lift using your legs is way more than your back. Most people use a mixture of both and sometimes they’ll use just their legs. But if you were to try lifting the same amount you normally could with your legs but with only your back you WILL mess up your back. Your body will immediately contort to force your legs to get involved but if you were stubborn… bad news bears.
That’s why the safest way to do this is to just use all legs since the difference is large enough to cause injury if you’re not paying attention.
While you sure can injure your back muscles and that is a significant risk (due to the leverage disadvantages of your back muscles vs. your arms when pivoting on the spine), the main issue is your spine. It’s very easy to slip a disk, or otherwise onjure your spine, when trying to lift a heavy load with your back.
And “very easy” here is not a hyperbole. It really is VERY easy. People have thrown their backs out trying to lift trivial weights, usually specifically because the object was so light that they didn’t even consider it “lifting”. It’s usually due to repeat strain.
If you lift with your legs, back straight, that force is supported vertically, which is the direction your spine is strongest. It also means your back muscles don’t have to do such a disproportionate amount of work.
Imagine yourself as a digger. Your muscles are the hydraulics and your spine is the boom and arm.
Now you can make the hydraulics stronger and lift more weight, but the boom and the arm can hold only so much weight, especially their joint. Under enough weight they will just crack.
The same goes for your spine, muscles can support it to some extent and training your back is good to prevent injuries, but at some point, these joints will just give in.
The biggest issue with lifting with your back is causing damage to the spine. It’s less of an issue with strength more of an issue with how bodies fit together.
Think of a spine like a bunch of independent things stacked on each other with some string running through it. It’s strong in the vertical axis, but when it starts bending there is only so far it can bend before something slips out.
An easy example is a bunch of books stacked from waist to chin. You can pretty easily press down on it with a lot of force. But try keeping them together while the top ones are bent over 30 degrees and then apply the same force.
Sure you can kind of keep the stack together with stabilizing it, but it’s much easier to have a book slip out than if the force was just vertical.
This gif also [illustrates it. ](https://imgur.io/gallery/cRtqM)
More stable is better since unstable is how back injuries happen.
Back muscles can be strengthened, but your leg muscles are already the strongest on your body and lifting with those keeps the back in a more stable position.
You can strengthen your back doing exercises like the deadlift, but bad form while lifting places undue stress on your spine no matter how strong you are.
It’s not a matter of strength, but leverage.
The muscles in your back attach to the spine basically running parallel to the spine, and onto those little wings in the vertebrae.
Lifting a 50lb box out at arms length and lifting wth your back puts nearly 800lbs of force on your spine due to the ‘leverage’.
Stronger muscles don’t really fix this. The bones and joints (disks etc) that make up the spine can only take so much.
To fix the issue you need even stronger materials for the spine and joints, and changing the actual geometry of the muscle attachments.
Lifting “with your back” means putting effort on your spine that is not up/down it. See, your spine is very strong with *compressive* forces, or forces that try to make it shorter. This is what gravity does all day to a spine that is upright, and it is what it was ‘designed’ to be good at. But once you add force to the spine in a different direction (such as leaning over and adding weight perpendicular to it, or twisting and adding weight to that twisting), you are straining the spine in a way that it is *not* strong against. And because the spine is so strong one way but weak this new way, your mind and the rest of your body are unprepared for this new weakness and you are more likely to try something you aren’t actually strong enough for.
Combined with how many sensitive nerves are in the spine (things that modern medicine can’t fix quite right), it is really easy to injure your spine (and the muscles/joints around it) in ways that will hurt for the rest of your life whenever you use your back in a way that is not simply compressive. So “lift with your legs” is an instruction to adjust your lifting strategy so that the spine stays vertical, and simply strengthening the muscles doesn’t strengthen the bones/ligaments enough to make it any safer.
It’s a bit of a misnomer. Even well trained weightlifters will massive activation of back muscles during movements like a dead lift or a squat. The use of back muscles is one of the major reason those lifts are done in the first place.
The bigger issue is that poor lifting technique puts unnecessary stress on joints. It’s not impossible but it’s hard to damage your muscles in a particularly bad way. It’s pretty easy to tear tendons, ligaments and cartilage and those tissues heal extremely slowly, and badly. So when you’re lifting things you want to position your body so that forces are primarily directed down bones and muscles and minimally on tendons and ligaments or across bones.
The human torso has evolved to let you stiffen it. When you do that can put it in a position where any weight near the top applies force directly down your spine. If you let your torso bend the forces don’t go down your spine evenly.
There are a few common mistakes people make when lifting heavy things. One is to leave the legs mostly straight and bend at the hips and lower back. This is often referred to as “lifting with your back”. When you do this the forces don’t go straight down through the bones of your spine, they go across your spine. The spine is much weaker in that direction.
The other mistake people make is to have their hips too far forward. That puts too much stress on the knees. Scooch your butt back like your really trying to send a fart flying across the room.
You absolutely can strengthen your back muscles and lifting heavy things is a great way to do it. If you lift with poor form you tear soft tissues instead of exercising your muscles.
The back muscles can be strengthened, but the other parts of the back- the discs of soft tissue between back bones and the ligaments/tendons attached to the back can be damaged easily, especially if they’re isolated while lifting, as compared to proper lifting technique where they work together.
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