When I ran in my 20's I had an average RHR of 48. Now I'm 40 and my RHR is about 68. I haven't run in over 10 years and my cardio usually consists of step aerobics, some interval training and some hi-lo, mostly Cathe. Due to the holidays, and my current respiratory infection, I've slacked off on the cardio but plan to pick it up again as soon as I'm better. Should I do more interval training, longer cardio sessions, or shorter ones at a higher intensity? Running is out! I totally burned out on it and have vowed to never do it again! TIA!