@bonanzaman
That is why I posted best to follow your doctors advise. I was advised by my Mayo urologist, R/O and my PCP not to bike ride even before my biopsies and was diagnosed with cancer. Why? Your weight is down on the area that pushes up into prostate area. So I was having PSA rises and even then was advised not to bike ride prior to PSA testing.

I was cautioned and reminded again when markers and Space/Oar were put in. And cautioned again when radiation started. Bottom line my doctores were telling me not to do anything to cause irritation to my prostate or affect the markers or Space/Oar.

We are all different and have different anatomies even though may be small from one person to another. The markers you mentioned are implanted into your prostate to allow alignment of your prostate when you have your radiation. Just think about another area of your body where you would have had markers implanted into that part and then put your body weight on that body part or subject it to vibration and jolting like you get from bike or motor cyle riding.

You did not mentioned Space/Oar. Did you have that? It is not implanted into prostate but between prostate and rectum. It takes time for it to hardened. But also I was told bike riding could cause it to move.

I was training and doing Sprint Triathlons. I changed to just walking and swimming. Do you have access to a pool to swim? Walking is fine. Light weights, stretch bands. These were things mentioned to me to keep doing.

You mentioned you are on hormone treatment. I cannot help you with my experience with hormones and how I dealt with them as did not get them. However you are correct from what I have read from others the hormones can be a real serious side affects for some.

Again talked to your doctors about things you can to to offset the hormones, exerercises to help with muscle mass, and things that you can do that would not cause possible issues with your prostate.
Good luck!

Try resistance bands.