I was also taking Lisinopril/HCTZ 20/12.5. Started getting into shape last December. By spring, I was running out of energy during the day. Almost passed out one morning while bending over stretching. Started checking BP every morning. I was shocked at how low it was. After consulting with RN at work, I tried stopping the Lisinopril/hctz. BP stablized at 120 over 70 after about a week off med. And stays there or below unless I am working long odd hours.(long hours, hard work, swapping from day to night back to day and sometimes repeating. All in a short period of time) BP will get UP to 140 over 90 in this type situation.
May not be able to get off beta blocker. But I going to ask doc if I can or if there is an alternative that will do same job without slowing me down so much. And I am going to get a HR monitor. One other thing, when I ride, the longer I ride, the stronger I get and my breathing gets better the longer I ride. At mile 20 I am riding much stronger than at mile one. Even at mile 30, I can ride better. Legs getting tired, butt starting to get a bit sore and feet starting to hurt a bit. But I am pedaling harder than early in ride. Almost like flipping a switch at mile 10 or so.