Shameless plug: I work at fitness startup, MoveWith (https://www.movewith.com). We are focused on creating audio fitness classes by some of the best instructors. I know that sometimes I don't know what I should do so for me it has been really helpful to have an instructor in my ear guiding my workout, I am biased here of course ;).
I have created a free gift trial for the Hacker News community (no credit card required) to try it out. Hopefully this motivates people to get moving! https://www.movewith.com/redeemgift/hackernews :)