打卡 (punch-in) originally meant "to record the time your present at your workplace" and it is an obligation
Later, people borrowed this term to describe "visiting a place that's considered a must-see place by the general public." As if it was an obligation like you are obligated to go to your workplace
For example, if you go to Paris, Eiffel Tower is a must-see, according to the general public. When you actually get there, you would say "来埃菲尔铁塔打卡了" (I have punched in at The Eiffel Tower) as if you have completed an obligation.
今天的锻炼打卡了
I don't think it is a correct usage of 打卡 in this sense of 'completed an obligation' - The general public doesn't consider exercise a must-try thing
Typically we 打卡 at must-see places or at places that you can try must-try things.
Example:
来到兰州自然要去兰州拉面店打卡了 (When you come to Lanzhou, you have to go to the Lanzhou Ramen shop to check-in)
' That's my exercise done for the day.'
這是今天份的锻炼了