3x20 is potentially a bold move from a relatively untrained state. Maybe sart with some 1 hour SS worksouts that are more broken up and incrementally increase from there. Are you following a plan?
That's a big jump and a classic error for most people coming from outdoor riding, I did the same when I started. Dial it back to MV or LV + z2 or SS rides.
3x20 is potentially a bold move from a relatively untrained state. Maybe sart with some 1 hour SS worksouts that are more broken up and incrementally increase from there. Are you following a plan?