New research might help explain why some people have trouble getting off the couch. Experiments on rats suggest there could be a genetic predisposition to laziness.
A group of scientists put rats in cages with running wheels — a subtle suggestion for them to start exercising — and recorded how much time each spent running during a six-day period. They then bred the top 26 runners with each other and paired up the 26 laziest rats. This selective breeding process was repeated through 10 generations, and researchers found that rats in the more active line were 10 times more likely to run than rats in the couch potato line.