Can sleeping bears keep astronauts strong? Carrie Straight 05.03.01 Imagine not eating, drinking, or even going to the bathroom for 5 to 7 months. That’s what happens to many black bears (Ursus americanus) while they hibernate. All they do during that time is sleep. If a person did not move around for that long, he or she would loose 90% of their muscle mass. We wouldn’t even be able to stand up, but not bears. After their long winter's nap, they are ready to hit the world running. If a person or a rodent (mice, rats) stays inactive, some of the cells that make up our muscles disappear. This does not happen in black bears. Scientists found this out by hooking a machine to the sleeping bears. The machine measured their muscle strength. It showed that the tested bears lost only 23% of their pre-hibernation strength during hibernation. This observation revealed that bears keep their muscles in shape while they sleep. How do they do it? Their workout during hiberanation may include shivering and other involuntary muscle contractions, and they reuse some bodily wastes to make proteins for the muscles to use. If scientists can figure out how bears keep their muscles going while they sleep, they may be able to help people that are bed-ridden for a long time or those with diseases that hurt their muscles. Harlow, Henry J., Tom Lohuis, Thomas D.I. Beck, Paul A. Iaizzo. 2001. Muscle strength in overwintering bears. Nature 409: 997. ©2001 The Aurora Collection, Inc. All Rights Reserved. Site Development by: Interactive Multimedia. Inc.