My guess is that they didn't push them beyond the level where fitness mattered. Sort of like having a group of people run a couple of laps around a track - whic

My guess is that they didn't push them beyond the level where fitness mattered. Sort of like having a group of people run a couple of laps around a track - which even sedentary people could probably manage without much stress on their bodies. In the article it was stated that rats do not like swimming in cold water and so they are apparently testing the affects of that kind of stress rather than just the stress of physical fitness.