Subject: Muscular response to physical exercise

(A clarification of 992896064.Me at your request)
I have noticed that some people can perform physical exercises with relative 
ease: They might be able to jog for long distances. Yet, even after many 
attempts to swim, they reach exhaustion after less than a minute and they have 
to rest. How can we explain such a phenomena? I know this is common, but find 
no article that mentions that. Did anyone ever make a research on that? I know 
you do not provide medical advices. If you are afraid this is what I'm looking 
for, I will be glad if you refer me to an article that I have probably missed. 
This is for general understanding only.

Re: Muscular response to physical exercise