Sometimes slow is faster, I’m 65. I only go as hard as I can without injuring myself. I choose consistency over intensity at this stage of my life. When I was a youngster I ran too hard too much time with my heart rate in zone 5. Therefore no matter how hard I trained, I had an aerobic deficiency. Didn’t realize you needed the majority of your cardio training with your heart rate in zones 1 and a little bit in zone 2.