mschwett 

some research has shown that the primary determinant of the condition worsening is total activity, as measured for example in mets - but for most the level which would lead to ongoing damage is higher than say, simply walking casually all day for your whole life. competitive sports and intensive endurance training has been shown to result in progression within a few years for many. for me, it took much, much longer, and i'm gene negative to the genes most associated with the condition. your idea is probably the right one - although there's no determinable line there is a level of activity which doesn't trigger the muscular strain and subsequent reconstruction that equates to damage with this condition. the standard advice is no exercise other than walking, light yoga, body weight type stretching or resistance, etc. i've done that for almost 10 years, and cycling seems to offer the advantage of easily tailored exertion levels regardless of terrain thanks to the wide range of gearing and speed available. running, not so much - running up a hill is hard AF for me no matter what, in a show-stopping way.

longer rides in lower zones are likely better than even short intense efforts:





my doc has recommended an average of as close to 100 as possible, no competitive anything, stop if it feels "too hard" etc. heart rate is a poor proxy for cardiac strain, unfortunately, without knowing a lot of other things but it's the only metric easily tracked while riding an outdoor bicycle. i'm going to do a stress test with echo later this month so at least they'll be able to revisit blood pressure during exercise, rhythm, o2, ejection fraction, etc. i'm guessing it's going to show that things are slightly worse than they were 10 years ago through natural disease progression, with no way to know what things would have been if i hadn't taken up cycling.