How do astronauts regain their strength after long periods of time in space?

The same type of physical therapy that people often undergo after an accident. Walking, bicycling and swimming are usually the 3 most common activities. Eventually they'll add some very light weights in hand or around their ankles. Push ups and sit ups when they're strong enough.

There's also something called an "anti-gravity treadmill" where they enter into a pressurized chamber to work out in, which simulates lower gravity and puts less strain on their bodies. I would imagine they alter the intensity as they recover.

http://en.wikipedia.org/wiki/Anti-Gravity_Treadmil...

Uh, yah. You ever pay attention of the Mir area Station. Russian cosmonauts stay aboard it for over a three hundred and sixty 5 days. (It not exists.) The worldwide area Station has some astronauts who've lived on board for numerous months. The human physique can not tolerate 0 gravity for prolonged classes of time.

Excercise both in space and on earth.

Special diets help too.

A cool youtube channel that shows you many different things in space. Here is one of his videos where they show you how they exercise in space. > http://www.youtube.com/watch?v=Wam7poPzG1w

Exercise. It's as simple as that.

exercise

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