Per Dan Espen:
With straight, really good exercise like weight lifting,
the exercise itself will feel punishing. Not good.
....
I've always found increasing muscle mass or tone a delayed pleasure.
You have to balance short term pain against long term rewards.

I have found that, with strength training, there is room to make it at
least neutral while actually doing the reps - and pleasurable afterwards
as the pump sets in. I'm not saying it's the greatest thing in the
world, but it's something I can deal with 2x per week for a half hour to
supplement the 1 hour cardio I do on the other days.
--
Pete Cresswell