There wasn't a moment in time where it was casual walking at exactly 2 miles per hour, I was simply describing an average if you consider the total distance ove

There wasn't a moment in time where it was casual walking at exactly 2 miles per hour, I was simply describing an average if you consider the total distance over total time. I was also going up and down a lot of elevation and stairs on that day. I think you would agree that walking up stairs would sufficiently elevate your heart rate to 150+ bpm easily even if you are going slower than 2 mph. Thank you for your concern though. I had an EKG done at my annual physical and spoke with a medical professional about how my maximum heart rate has been 218 bpm during a specific gym session, no caffeine or other stimulant use. I use a polar h10 with the pro strap and have seen 210+ over multiple gym sessions. He said don't worry about it. Resting heart rate and how quickly you return to your resting heart rate after exercise is the main measures of health and fitness. And just to be clear, pushing myself to a very high heart rate was very much intentional, I was very aware of my breathing and watching the reading on a second by second basis and not pushing myself to any sort of injury. I was able to do yoga that evening and do a less intense 90 minute workout the next day. Pushing myself in that way isn't a thing I do regularly. https://imgur.com/a/yfV8FYc https://imgur.com/a/yfV8FYc As you can see it's relatively smooth as it's over an hour, no sudden spikes in my heart rate. This was on a stationary bike. This was recorded on a different day, not the 20 mile day. 150/218 puts 150 at 69% which is comfortably in the aerobic/light HR zone for me. I calculated my max HR to be 2.6 standard deviations away from the average based on https://www.sciencedirect.com/science/article/pii/S0735109700010548 https://www.sciencedirect.com/science/article/pii/S073510970... . My resting HR is in the mid 60 to low 70 but has been creeping up over covid since I stopped exercising. I guess the average person doesn't have as high of a max HR and so the 150 would be off. For most people beginning their fitness journey, worrying about HR zones is pretty far down on the list of priorities.