I'm wondering if anyone knows if heart rate is the true measure of calories burned. I have a short hike (cross country) that I do first thing most mornings. It takes about 25 minutes, starts with a gradual uphill with a very steep part in the middle and ends with a contour back down to the house. What I usually do is get up, stretch in the hot tub for about 15 minutes, and do the hike with my dog. First thing in the morning after the hot tub, I'm not all that energetic, but it's still a great way to start my day (shinrin-yoku--forest bathing
What I've noticed is if I do this exact same hike mid-day, I have WAY more energy and my heart rated doesn't seem to be as high (I don't have a monitor). So am I burning fewer calories than I do in the mornings? Not that it matters too much, but I'm curious.