You walk 4-5 miles during a professional round, often up and down very hilly courses (like the current U.S. Open).
I'm old enough to remember dial telephones 25-cent-a-gallon gas and The Honeymooners.However thanks to doctors' orders I walk...at a fast pace...at least 4 miles a day on a route which includes several big hills.As a result my weight is down,my blood pressure is down and my diabetes is under much better control.
Yes,golf may well require some upper arm strength.It seems highly likely that it requires a knowledge of physics and geometry.
Center fielders are athletes.Wide receivers are athletes.Those competing in he 1,000 meter dash in he Olympics are athletes.
I can easily walk 4 miles despite my age and my artificial hip.Bu I'm no "athlete".
And I can't sink a 30 yard putt despite the fact that I have more than enough upper arm strength to get the ball to the vicinity of the hole.
Brandt Snedeker wore a device in practice to see how much walking he would have to do this week and the result was nearly TEN MILES per day on this course due to the length, terrain and how the layout is. The days of Craig Stadler and John Daly being competitive are over. All of these guys work out with fitness training routines.