I am 70 and the only exercise that is comfortable for me is a brisk walk on local roads with hills. I used to have hypos and have to stop and eat glucose tabs and wait for them to start working, and then walk home, or call my wife to come get me.
Now i walk less than 30 minutes after a meal. The carbs in the meal keep me from having a hypo. The carbs wotk faster than the premeal bolus so it works out well. if your workout is more strenuous than a walk, or you exercise for a very long time, then you should test frequently and always have glucose tabs and your meter with you at all times.