69 year old male, diagnosed with PV in 2021… I’ve been on HU since April 2021… My current dose is 1500 mg M,W,F and 1000 mg the other 4 days… My oncologist focuses on HCT in my case and that has been at targeted levels for the last 2 years… I get monthly blood tests and my RBC and platelets are consistently flagged as low… Despite this, I bike daily and energy levels are excellent… I don’t like the idea of taking so much HU but the only side effect I can attribute to HU is thinning of my hair… I will say that I do protect against exposure to the sun and use sunscreen and wear long sleeves when outside… HU seems to impact people differently… I don’t bike/exercise in higher elevations so can’t comment on that.. That’s my input… It may take a while for you to see how HU may or may not effect your exercise routines.. Best of luck to you..