Zero-gravity during the 1974 Skylab 4 mission.
Credit: NASA

This amazing image comes from the U.S. space agency. In it, astronaut Gerald P. Carr, who was the Commander for the Skylab 4 mission, demonstrates weight training in zero-gravity. Here, he balances astronaut William R. Pogue, who was the pilot, upside down on his finger.

We all know that gravity is rather important. It keeps us all on the ground and stops us from constantly bumping into one another…but it does a lot more than that. On Earth, gravity helps to regulate our blood flow by pulling our fluids down towards our lower extremities. Of course, it doesn’t stay there (if it did, we would die). Our body works against gravity to ensure that blood is pumped to the rest of our vital systems. Ultimately, we are evolved to suit this gravitational environment, so it’s not surprising that things change in space. Because there is such low gravity in space, our bodily fluids are free to roam about as they please. This is known as “fluid shift.” It sounds a little horrifying, but the results are mild. Due to the increased amount of blood in the head, individuals sometimes get a stuffy nose and a puffy face…a space cold, if you will.

The impact on the muscles is a little more traumatic. On Earth, gravity helps keep us rather fit (assuming that we get out and walk every now and again). In fact, the simple act of standing works your muscles; at the very least, you are forced to carry your own weight. The gravitational pull that your body is forced to work against ultimately helps to keep your muscles from deteriorating. However, because you are weightless in space, it is rather easy to move your muscles. As a result, they don’t get a healthy workout. Muscles quickly weaken and lose their strength, which is why astronauts on the ISS have to work out for at least two hours each day to prevent muscle loss (see, being an astronaut isn’t all fun and games).

If you are unfamiliar with the program, Skylab was the space station program that was a kind of placeholder between the Apollo and shuttle programs. It was assembled on Earth and launched on the last flown Saturn V. There were three crews launched in 1973. The Skylab 3 crew spent 60 days in orbit, which more than doubled the previous spaceflight record. Skylab 4 (with Gerry Carr, Bill Pogue, and Ed Gibson) launched on November 16, 1973. Their total mission lasted 84 days.

Unfortunately, their initial work plan was a bit brutal, as reports claim that it called for a total of 6,051 working hours between the three men (if you do that math, that means that they were literally working 24/7). The astronauts were expected to work during mealtimes and disrupt their sleep in order to complete experiments. This may seem a bit unbelievable, but if you look at the NASA mission statements for Skylab 2, the astronauts completed a total of 1,081 hours of experiments over the course of 54 days, and on top of that, they completed 13 hours of extra-vehicular activities.

Conditions on Skylab 4 were so bad that the astronauts eventually mutinied. Well, sort of. The astronauts reportedly announced an unscheduled day off to get some much needed rest. They turned off the communications radio, and they spent some time recovering from the grueling schedule. But at this image shows, it wasn't all work and no play.

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