It seems that lifting things with the back comes intuitively to humans. Every year we conduct training / safety programs aiming to get folks to lift with their knees rather than their backs.
So my questions are :
Is it nature or nurture for humans to lift things with their back instead of knees ? I.e. are there human cultures where lifting with knees is the norm?
How do our closest relatives (apes) lift heavy weights ?
You should lift with your knees and your back. In fact, you’ll have a very hard time doing either separately. The biggest problem for the casual lifter is twisting. Move your whole body while lifting if you have to change angle. Don’t just turn at your hips. Another problem is lifting with a curved back rather than straight. A see saw or crane with a curved arm isn’t very effective at supporting their loads. A flexible back is a bad idea, too. Brace your back by taking a deep breath and tightening your abs. This is what those weird suspender belts they make warehouse personnel wear are supposed to help with. And of course, people can get better at all this with practice. Somehow OSHA-type bureaucrats have distilled this all down to the misleading slogan “lift with your knees, not your back”.
There is some cultural component to every human behavior, but lifting is heavily constrained by the laws of physics and the anthropometry of the organism doing the lifting. I would be surprised if there were a lot of variation by culture. The twisting and loose back issues I listed above are about the main ones you’ll find among the general population, where you’re not looking for perfect form to squeeze every last pound you can get out of a squat or deadlift. Those issues are corrected by more experienced lifters. If there is cultural variation, I’d expect it to be between manual laborers (and gym-goers) and the rest of the population which doesn’t lift heavy objects on a regular basis, rather than something that changes from society to society.
I have no clue how other apes lift. Like you, I’d be interested to see that data.
Lots of stuff here, I’ll start with what I was told by the occupational safety instructor at work.:
Quadrupeds can carry incredible weights for long times without tiring across their 4-limbed supported back. Humans are bipeds, and bending our spines forward, unsupported, without a counterweight, is simply a stupid design for weight carrying. A crane designed like the human torso would get the inventor laughed at, and then arrested. Humans must be taught this in Occupational Safety seminars, because reaching forward is just so easy and intuitive. But simply bad for you.
As for apes, one has to start with the question: what do they lift? What is the heaviest item they carry, ever, and why? They are incredibility strong, because of different muscle attachments and muscle biochemistry (I heard that here, not sure how true.) They build much weaker structures, of much flimsier items, than humans do on a bad day. They never co-operate to carry a heavy weight (wolves do, carrying heavy meat back to pups in a den in the mouths of more than one wolf.) I don’t believe an adult chimp will carry another adult, even if sick or injured. Their social conventions don’t negate their breeding competition to that extent.
I would guess that other ape species very rarely have any reason to lift anything heavy.
The golden rule when lifting any weight is to be sure you know where you can put it down safely.
Finally, a use for my seven years of study in physical anthropology!
Humans are, frankly, a big mess as far as design goes. Humans gave up a lot to be able to stand upright and walk as efficiently as we do. That we can lift the weight we do while still standing on only two limbs is a minor miracle. That we sometimes overextend our ability and injure our backs is not a surprise.
Apes (let’s include gorillas, orangutans, and chimpanzees, but exclude gibbons) are very poorly adapted for carrying loads while walking on two limbs. As semi-brachiators (i.e., generally walking with the aid of their knuckles on the ground), they don’t have the right posture. They can easily pull, push, or otherwise shift tremendous weights, but carrying a 40-kilo box for 100 yards in any way other than under one arm is a real challenge for them.
I recently read an article about the “proper” way to lift something. It said it didn’t matter if you lifted with your back or knees. What was most important was ***keeping the item as close to your body as possible ***while lifting it.
I’ll see if I can find a link to the article.
One risk for modern humans is that there’s a big difference in core strength between someone who’s fit and someone who’s sedentary. Fit people will have stronger muscles that can hold their bodies in proper position with less risk of injury. The typical office worker will have less core strength and is more likely to be thrown off balance or be in a more twisted position when lifting a heavy weight. So then we have the OSHA videos telling people how to lift with less risk of injury.
Another thing is that if you spent a big part of your life lifting heavy things, you would likely be much better at it as you learned and adapted to what is easiest. So you can’t necessarily draw conclusions based on how sedentary office workers lift things. If we look at cultures where they have to carry things for long distances, it is often done by carrying it on their head. Most office workers would find it quite difficult to carry a large jug of water on their head, but people who grew up like that can do it quite efficiently.
Actually, they can’t. They are functional, of course, but it turns out the body is not better adapted to carry things on heads than it is to carrying them other ways.