Hi there. I'm 34, a few extra pounds, and I've really been working out to improve my health and hopefully lose some weight (for over a year now consistently and sporadically before that). I'm using primarily an incline trainer (treadmill with higher incline capability) doing slow walks at high inclines and sometimes faster walks at lower inclines, and I had a question about heart rate.

I know the most common formula for max heart rate (MHR) is 220-(age of 34)=186 bpm, so I try to target my HR between 50% (93 bpm) and 85% (158 bpm) of that max. However, I'm working with Jillian Michaels programs to build endurance, and at this point they sometimes cause me to exceed the 158 number and approach 186 (100% of max). Generally, these are ~30 minute programs with less than a third of it above 85% and only a few minutes near the actual MHR.

For example, today I did a 30 minute program. I'd say ~20 minutes were at or below 158 bpm. But for that other ~10 minute period, I was over 158, generally in the 160's/170's. I didn't get into the 180's today, but it does happen sometimes. I feel absolutely fine (like I'm working hard of course, but good) during this time. I even tested myself by saying a paragraph out loud (the talk test) while I was over 85%, and it was relatively easy to do (maybe a tiny bit winded but nothing extreme). If I wasn't wearing a heart rate monitor, I would just be thinking I was getting a good workout - there were no alarming sensations or anything.

I can do easier programs where I don't go over 158, but it just feels a little too easy and like I'm not making progress. I'm trying to get in better shape, and I feel like the programs I'm on that raise my HR above my 50-85% range are actually a bit challenging and I feel more accomplished when finished.

I also suspect, since MHR varies, mine might actually be higher than the 186 bpm estimate (I've also *very* briefly exceeded it before), but I've always been a bit too scared to try to find my absolute max by working at my limit (as my dad died of a heart attack after exercising in his early 50's).

I've read two schools of thought. One is that, unless you have a specific cardiac condition, heart rate monitors are overrated and you should go by how you feel, not your heart rate, when exercising. But I've read other things that say you should never go above 85% of MHR or you risk overtraining, reducing your heart's ability to recover after a workout, possible arrhythmia, and musculoskeletal injury. I just don't know what to believe.

So my core question is, is it safe for me to be pushing myself with these workouts (up to the MHR of 186 bpm) since I feel good? Or should I do the easier workouts even though it feels like I'm not getting as good of a workout as I could.

Thanks for any help/guidance you can provide in the complicated and confusing issue!