About 40 years ago, what did researchers discover when they studied people who engaged in anaerobic exercise?

One of the primary observations made by the researchers after forty years of studying people that are consistently engaging in the anaerobic exercise was that these people are mostly likely much fitter and leaner. In addition, anaerobic exercise is a type of exercise wherein the body usually demands more oxygen that its capacity to hold.

Ithink it's a, but i might be wrong