I an 79 Years old , exercise 3-5 days a week, have a resting HR of 56 abd take a blood pressure medication. My questions are:
Penn State research says you can get a training effect from a minimum of 12 Min in THR zone.Can I maintain my aerobic fitness with 3 12+ Minute workouts in THR zone which is 99-125 BPM (65-82% MHR)? Using the Tanaka formula my MHR is 152.7 BPM. Could I maintain my aerobic fitness with 2 days per week with 25 Min each workout in my THR zone ? and finally can I count Passive rest as exercise duration if I am still in my THR zone ?
Good question. The answer is...maybe. You'll have to try the two programs you described to see if you maintain your aerobic fitness. Remember, these type of studies are done on very few human subjects. Researchers published this specific recommendation because that is what their study showed with the subjects they had. It does not mean that you will achieve the same results. You may be able to do less and maintain your current aerobic fitness level. You might have to do more to maintain your current aerobic fitness level. I believe we take this kind of information and think it applies to everyone, when in fact, it is often extrapolated from a very small sampling of individuals (often college age individuals). It is also not an exact science, which contrasts with what we want it to be - an exact science. It's really difficult to say for example, if 12 minutes is the bare minimum one needs at x-percent of PMHR to maintain aerobic fitness. For some people, yes. For others, it may be 13 minutes. Or 15 minutes. Or the the percent of MHR may be + or - 10 to 12 bpm from any formula used to calculate MHR. Unless you've had a max heart rate test done, we don't know what your MHR really is...it's just a guesstimate. And monitoring HR during exercise is often littered with inaccuracies.
Rather than obsessing over such detail as you described in your inquiry, I might recommend you just start enjoying your workouts and celebrate the excellent fitness level you have. You're already at the top level for people of your age in terms of cardio fitness. Being concerned that you must do x-number of minutes at y-percent of your MHR or you won't maintain your C-V fitness level is important if you're a competitor in the senior Olympics and you want to win a race (maybe you are a competitor). But I wouldn't worry so much that you're going to lose your aerobic fitness as long as you maintain a consistency which it seems you have. Even if you follow those precise guidelines from Penn State, you will still lose aerobic fitness capacity just due to the physiological declines with aging. You'll just lose yours at a slower rate than most people because you're so fit and motivated to stay that way in the first place, and because I got the feeling you will be consistent in your aerobic exercise as well.
May not be the answer you wanted, but any response that says yes or no to your inquiry, or any other recommendations you hear about, are always just general guidelines and recommendations. They are never exact for everybody. I wish they were. It would make it so much easier to know just exactly what the correct formula is.