When it comes to exercise, many people seem to fall into two distinct camps: those who love a vigorous, sweat-soaked workout and those who view it as a form of torment.

With hopes of getting more people up and moving, scientists are looking at the body's biological and chemical processes for clues to understanding what's behind differing attitudes toward exercise. That could mean there are factors beyond motivation and discipline to explain why some people enjoy exercising and others don't.

One finding so far: How people interpret their body's sensations during and after exercise plays a large role in whether they enjoy it. Also, researchers at Iowa State University found that people's physicalcapacity could be much lower than many realize, so many people push beyond their limits without realizing it. For example, for sedentary people, just cooking dinner could count as exercise and they need to build up to even walking, the researchers found.

Dan Cederholm has tried for years to find some type of exercise he could stick with. He finds the gym boring and basketball and baseball leagues unappealing. As for running? 'My shins always hurt like hell,' says Mr. Cederholm, 38, a Web designer from Salem, Mass.

His friend Rick Johnson, on the other hand, competes in 20 road races a year. He remembers that even as a kid, when he was told to run a lap during gym class, he would ask to do extras. 'To me, it seems very foreign to say I don't enjoy sweating or running,' says Mr. Johnson, 41, an editor who also lives in Salem.

From couch potatoes to Olympic athletes, everyone has a physicalcapacity for exertion, beyond which the body becomes stressed and begins to feel bad. How much stems from genetic factors