Astronauts who spend months on the international Space Station need to take care when coming back to earth that they don’t do so with too much of a jolt. Joyce Keyak, orthopedic surgery and biomedical engineering professor from the University of California Irvine says that astronauts who are up there for months at a time are losing “alarming amounts of hipbone strength” (press release).

Alarming indeed: “on average, astronauts’ hipbone strength decreased 14 percent. Three astronauts experienced losses of 20 percent to 30 percent, rates comparable to those seen in older women with osteoporosis,” we are told.

It has long been known that the microgravity conditions in space vehicles cause bones to weaken. But density, rather than strength, has been the measure used so far, we are told. Bone strength, as measured by Keyak’s computer programme hooked up to a CT scanner, deteriorates more than bone density. This loss of strength will make those astronauts more susceptible to bone fractures in later life, especially in their hips, which are most vulnerable.

Back in 1985, a Nature News and Views article, The skeleton in space, by A. W. Goode and P.C. Rambaut, stated “With astronauts now making multiple short trips and with the prospect of their undertaking recurrent 3-month tours of duty on the Space Station, an understanding on the influence of gravity on the skeleton becomes urgent.”

So here we are, 24 years later, being alarmed. There’s progress.

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