Actually, your cat isn't as fit as you may think. Housecats of all breeds sleep very lightly for about 75 precent of the time spent slumbering. They are expressing a genetic predispostion to light sleep to better avoid predators. Their eyelids may even be partially open during this sleep. They do sleep soundly the other 25 pecent of the time. Many housecats are obese or at least overweight, primarily because they don't get enough exercise for the calories they consume. If your cat was required to suddenly exercise vigorously for an extended period of time, you would observe fatigue compared to his brothers and sisters that are feral cats or at least fending for themselves by hunting...