Myocardial ischemia and safe exercise limits

I am interested in finding others who are in the same situation as I am who would like to share their experiences.  I am going into retirement just as I have discovered that I have coronary disease.  A significant part of my retirement is playing sports such as tennis.  I have multiple blockages in branch arteries up to 90 percent, but the cardiologists advise me that stents are not the answer and I need to avoid virgorous exercise.  It has been difficult for me to understand their definition or vigorous.  More accurtely, their answers have been somewhat circumspect.  I have found one publication from Germany titled "Myocardial ischemia during physical exercise in patients with stable coronary artery disease: predictability and prevention."  This article is pretty much right on although I am still trying to understand some of the terminology so I can interpret the results. 

So far I understand that the ischemia limit is around -1.5 to -2.0 based on discussion in the article and from my cardiologists.  There is discussion about two levels of exercise, one at 75 percent of peak heart rate and one at 95 percent.  But it is unclear to me if the peak heart rate was determined by myocardial ischemia limit of a more arbitrary limit set by age and resting heart rate.  Anyway, I have a number of questions and am hoping that there are others with the same interests.