If literature is too dense for you, I personally like to put on Dropkick Murphy’s Woodie Guthrie albums, Sixteen Tons, Rage Against the Machine, Question, Union Dixie, etc… If anyone has more leftist workout song suggestions, I’m all ears!
Come out ye Black and Tans (particularly the cover by Colm R. McGuinness)
Depending on how you choose workout songs, the Song of The United Front could work too. To me, pretty much any left song, from certain Dropkick Murphys ones to The Internationale, will do the trick. xD
Edit: Forgot about the Chemical Workers' Song. How could I.
I've considered doing literally this. I listen to audiobooks and podcasts while running, and there's a bunch of leftist writing I want to read... but I'm pretty sure that Marx and Kropotkin are a bit too dense for this to be a good idea.