I might be recalling something from a previous edition but have athletics absorbs acrobatics but it leaves tumble in its place as a dex skill specifically dedicated to being able to do things like dodge things and know how to break your fall properly, none of this ‘i make the jump with acrobatics because i do a flip in the middle’
Athletics then gets split into what I’m going to call might and stamina, might is short burst feats of power like lifting a boulder, putting on a burst of speed, smashing a gate or breaking out of a hold, stamina is used for extended exertion such as running, swimming, hanging from a ledge or carrying weights.
"Might" is a fun name for "Weightlifting". I would use Might for lifting the heaviest boulder possible, "bend bars, lift gates", and carrying a notably heavy load. For loads, I visually conceptualize it as one can carry the Size smaller without worrying about encumbrance. So a Large Horse with a Medium Human rider is without worry. And a Medium Human with a Small child is without worry. Then I translate a load of objects into an overall Size. But then I make special exceptions when carrying things like an amount of dense pure metal or coins, or awkward pole or other uncontained, unstrapped, unwieldy load.
For the sake of knowing when to use and Strength and when not to, Strength always applies to every body stunt. There is no reason to try subdivide it. Indeed, the use of Dexterity when it should have been Strength has caused many problems and confusions across D&D editions.
In my games, stamina tests are so rare I dont clearly remember the last time I required one or made one. If it ever did come up, such as running a marathon or whatever, I would use Constitution (Athletics) for it. I guess holding ones breath while swimming would be Constitution (Athletics), if for some reason the time became a test. But that hasnt happened recently. For enduring dehydration or starvation, I wouldnt use Athletics. Perhaps I would use Constitution (Medicine)? But again, it doesnt normally happen in my games.
"A burst of speed" is a normal part of running, so I would use Strength (Athletics) normally.
Hanging from a ledge is a frequent, routine, and necessary part of mobility and agility generally, so I use Strength (Athletics) normally. My rule of thumb here is, if a character is carrying their own weight it is Strength (Athletics). If the character is carrying an other character as part of the weight, it is Strength (Weightlifting/Might) check.