I am 53yrs old and have been riding my entire adult life. Up until this year I would typically ride 3-4 times a week and put in at least 100 miles during the week. At least one of the rides was some form of high intensity (e.g., competitive group, interval training). I get that your abilities decline as you get older, but this year I have started to experience extreme fatigue after every intense ride. The fatigue lasts 3-5 days after each ride. In addition, I have experienced headaches both during and after the rides. This has been going on now for 2-3 months. Early on I thought that I wasn't training enough, but I realized that wasn't the case. More riding resulted in more fatigue. Searching the internet I was unable to find anything that exactly matched my symptoms. I saw my doctor today and he is going to put me through a stress test and run some blood work. I wanted to know if anyone has experienced something like this or knows someone who has. I would really like to know what the root cause was. Thanks.