I think its because a finely tuned athlete's cardiovascular system has had more experience with hard physical activity for longer periods of time. Their body is able to make up for oxygen loss faster, because it has had more practice doing this. Physically unfit people however, do not get much hard core exercise, so they're bodies do not have enough practice regaining the oxygen in their system. They're cardiac recovery time is slower.
A small girl with a bow placed finely above her head.
She painted each detail with finely tuned precision.
She chopped the vegetables finely to add to the soup.
Finely ground pepper.
Sure, if they are finely chopped enough.
Finely ground tobacco is called snuff.
The noun 'onion' is a count noun:1 onion finely chopped2 onions finely chopped
She wore a finely carved jade pendant.
finely chopped is another way of sayying cut into thin peices
Some herbs can be roughly torn up while others need to be finely chopped before adding to a recipe.
Because it's a finely divided powder, and almost all finely divided powders are explosive.