how do anti-gravity treadmills work


Just heard about a good PT machine that removes the load of body weight from running to help healing after injury. Explanations talk of a pressure difference but don’t go much further or at least explain it so I can understand.

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It applies uniform pressure to the entire lower body, providing support and effectively removing some of the patient’s weight. It does this by putting patients in a special pair of pants which are attached to a chamber which is filled with high-pressure air like a balloon. The pants are the only flexible part of the chamber, so they want to puff up and out, but the patient standing in them forces them back down. This counteracts some of the patient’s weight, allowing them to strengthen muscles used for walking without needing to support their entire weight on them.

Basically, you’re a plug. You put on special shorts and get into an airtight bubble that comes up to your hips. You and your special shorts plug the hole, so as pressure is increased in the bubble, it tries to push you out, effectively lessening your weight to an adjustable degree.

Or in space, you lower the pressure so that the air outside tries to push you into the bubble, imitating gravity pulling you onto the machine.

It’s basically a chair or a sling that takes sub or all of the body weight.

Walking is actually a very complex behavior, particularly for bipeds like ourselves. The muscles and skeleton and joints have to carry your weight, make the correct moves, and apply force forward and backwards.

So let’s say you just had surgery on your knee. The joint is still inflamed and swollen from the surgery but they want to get the knee moving so that it doesn’t scar internally so badly that you can’t bend it. But the thing is your muscles are probably atrophied or you’re used to limping. So we want to train your muscles to move your body in the correct way .

As an aside limping helps in the short term but it’s actually quite damaging as it involves guarding, compensation, and unexpected impact in certain ways .

So what we do is we suspend you over the treadmill on your seat or whatever and first you start walking with virtually zero weight on your feet. The treadmill is actually doing most thoracic at this point .

When you get used to the motion and we’ve kept your range of motion big enough while your knee healed. Then we can start having you put weight on the knee. But we don’t want to go from nothing to full body weight, so as part of the plan you know we Make a plan for the rate at which we’re going to increase how much of your weight you’re actually putting down on your feet. And over the course of several weeks we can get you up to comfortably moving yourself around if we’re lucky .

In the olden days, as it were hahaha, we would just put you on crutches and tell you to walk as much as you could. And you just have to struggle with it and possibly end up re-damaging The joint .

But mechanically it’s just a way to hold your body weight up and control exactly how much of the body weight you’re actually holding up with the legs as you go through the motions of walking .

(I’m not a medical professional, this is not medical advice. I used the word we as a continuation of the example not as a claim of medical talent.)

Another way of doing this without a sling is to actually have you walk in a pool. Buoyancy holds your body up. And we increase the weight to you’re putting on your feet slowly by moving you to more and more shallow parts of the pool.