I am genetically predisposed to low testosterone made worse by endurance sports. At one point I had more estrogen than testosterone in my system. A doctor suggested I quit running and cycling as it was obvious the high mileage running and biking was destroying my T. Finally was convinced to see a urologist by a friend who said Testosterone would save me. I got put on Testosterone Cypionate 200mg a week. That first week felt great, I felt 15 again in all ways, went and ran a half marathon and felt like I could run so much faster. The second and third week the side effects kicked in, my heart rate shot up due to increase in red blood cells. I had to go and give emergency blood to get my hematocrit down. I started to gain weight as I started to retain water and my calves would get so pumped I couldn't finish a run. After much research, I found one post that suggested a proper dosage for runners. 100mg a week broke up into multiple shots a week. Things have gotten better but I still can't get the weight down and a run has become a chore. Seems to be the lower amount of test allows for running but doesn't do much for the other issues. It seems to me that I have to either chase after wanting to run and stay on low doses or not run and feel good on a higher dose. All I know is that if one was to dope testosterone is not the drug a runner would want to use, maybe a sprinter but surely not a marathoner.
Just my experience