Why do we hold our breaths when we push or pull on heavy objects?
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If by this you mean strained breathing, it’s related to how the body tightens up so as to create better tension. Think about it, if you were trying to create leverage against something limp, then it would be dampened, but if you’re trying to create leverage against something solid, more of the energy is transferred efficiently. You’re basically doing this with your body when you exert yourself on strenuous tasks
The point is that this also includes the intercostal muscles of the ribcage. As well as other core muscle groups. All of which are necessary for respiration
So when you’re performing a feat of strength, you’re both trying to tighten everything and also have parts mobile enough to allow things like breathing
There’s a thing called the Valsalva maneuver, it can actually increase core strength and protect your spine to hold your breath for a big lift.
But as a general rule, repeated lifting or for any duration of time you need to be breathing.
So I think its large an instinct to brace yourself, which seems to have some truth to it, but that instinct is counter-productive in a lot of cases
Think about a balloon or a tyre. The more air you put in, the greater the pressure and the stiffer the thing gets. This, in a sense, gives it more strength.
When we take a breath and hold it, we are inflating our lungs. This makes them stiffer, and pushes some of the other soft stuff in our abdomens about to make our bodies more rigid. This makes it easier to move the heavy thing.
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There are three thick muscular layers of the human abdominal wall. From inside to outside, the layers are called transversus abdominis, the internal abdominal oblique, and the external abdominal oblique. These muscles attach to the rib cage and the pelvis, providing tension to move the spine, particularly the lumbar spine. The lumbar spine is very important for weight-bearing activity including heavy lifting. In addition, contraction of these muscle groups compressed the contents of the abdomen, which are then displaced upwards into the diaphragm to move the diaphragm upwards and blow air out of the lungs. When you try to blow a strong breath (E.g. blowing out birthday candles), it’s the muscles of the abdominal wall that provide most of the force.
When you lift something heavy, your lumbar spine needs a lot of support. The muscles of the abdominal wall need to be tense so the spine can be fairly rigid. Achieving this tension requires a strong contraction, but that contraction would just blow air out of the lungs if you didn’t close your vocal cords to hold your breath. By holding your breath, you keep the lungs full of air so the diaphragm can’t move, which means the muscles of the abdominal wall can contract strongly and raise the pressure inside the abdomen. The high pressure in the abdomen, as well as the tension on the spine produced by contracting muscles, keeps the lumbar spine rigid, which allows you to lift something heavy.
This behavior must be learned. A newborn infant does not know to “bear down” (Valsalva maneuver) when pushing hard with the legs. But they figure it out pretty quickly. By the time your brain is capable of forming meaningful memories, you’ve already figured out how to use the Valsalva maneuver to lift/pull things, so you don’t even think about it anymore as a child/adult.
a tight core gives your muscles something to pull or push against. a floppy core gives very poor power transfer.
always tighten your core before lifting. failure to do so is why people ‘throw their back out’ when reaching down to pick up something lightweight like a shoe.
tightening the core can be done many ways, but taking a deep breath and lightly holding it like you’re about to sneeze will be the easiest way to tighten your core. once you get the feel of it, you should figure out how to breathe while maintaining a tight core.
I don’t think anyone did a real ELI5 so I’ll try.
Imagine a can of coke, when it’s closed it is a very stable structure, you can put some heavy things on top of it and it won’t break. But if you open it and empty it then the story changes.
Your torso works basically the same way. On the back there is the spine and back muscles. On the front and sides there are stomach muscles and ribs. On the bottom there is the pelvic floor muscles. And on the top there is the diaphragm muscle. (The one tied to our breathing)
To lift something heavy and to not round our back (rounding makes muscles less effective and can also lead to injury) we need to have a rigid torso, so all 4 sided need to be ‘tensed up’. However if you just do that then what you end up with is an empty can with rigid walls – quite stable but nowhere near as stable as a full and shut can of coke.
So add this extra rigidity and to be able to lift more weight and to produce more force in general the human body does the hold the breath manoeuvre. You get a breath in (fill up the can), close your throat and pucker your anus (close the can) and then proceed to lift heavy things allowing the force to travel from the ground and into the heavy object through your rigid body.
Lifters (like Olympic lifters or powerlifters or regular gym goers) use this technique all the time. Its called bracing or the valsalva manoeuvre. It basically gives you the ability to lift much heavier things much safer. It’s like a special “lifting” mode your body can go into for a few seconds.
We do it to brace our core. By bracing, it stabilizes and makes our trunk rigid, which ensures your body angles can produce force in the proper directions, rather than just collapsing
As others’ said, it makes your core more rigid which is necessary to transfer the force without just folding over.
What I wanted to share is what happens when you *don’t*. Because this is exactly what my wife experienced for some time after the birth of our kids… When you’ve had a kid in your belly for such a long time, all the muscles and ligaments have to stretch to make room, naturally. Once the kid is out, everything takes a while to contract again. During that time, a deep breath wasn’t nearly enough to fill up the room the baby had filled. As such she simply *couldn’t* make her core rigid for some time. Many hilarious moments were had when she would go to pick up a grocery bag or something, and just *fold over* lol.
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