wearing a hrm while hiking?

I think you should wear your hrm. You'll be amazed at how greater of a burn you will get than a normal day. Last time I hiked I killed over 700 calories in less than 90 minutes.

I guess it depends on how strenuous a hike and if you're carrying a pack and that sort of thing. I often wear my HRM when I hike. According to it, I burn something like 2000+ calories on a 3 or 4 hour hike. I failed to wear it either day this past weekend, though, when I hiked around 8.5 miles a day in the mountains. I wish I had!

One thing to bear in mind that is more relevant for an activity lasting hours like hiking (compared to 30mins on the treadmill for example). I believe in most cases the calorie burn will include your BMR cals so if you would have burned 70cals in a in hour lay in bed doing nothing but go hiking for an Hour and your HRM says you've burned 400cals then you've actually 'only' burned 330cals extra so don't eat back all 400. So a 30min blast on the treadmill and your cals are out by 35cals but a 5hr hike and you could be over-estimating by 350cals so the longer the activity the greater the potential to over-record calories burned.

Alternative view:

I've worn my HRM while engaged in recreational activities like hiking, and it detracts from my experience. I chose trails based not on where I wanted to hike but what would spike my heart rate. I was less likely to stop and enjoy views with my family because I wanted to keep my burn going. I got irritated when my HR was only 80bpm while on a relatively flat trail.

I've learned that my HRM is a useful tool for certain forms of exercise, but it can be a hindrance to the *real* reason I'm grateful to be fit: enjoying activities like hiking, canoeing, kayaking, biking with the people I love for the sheer joy of being active outdoors, not to achieve a calorie burn.

So, for what it's worth, my advice is to leave the HRM at home. Log the hike using MFP or don't log it at all, but have some trail mix while you're out and enjoy a beer (or two) when you're done.

For me, if I am hiking on a trail with little elevation gain, the intensity is too low for an HRM to be accurate when it comes to calorie burn, so I just record the hike as walking. If, on the other hand, I'm on a hike with decent elevation gain (say 1000' or so) then I use this hiking calculator: http://hikingscience.blogspot.com/p/calculate-calories-burned_22.html. It gives a conservative estimate of calories based on distance + elevation gain.

The MFP database gives crazy high calorie burns for hiking, so I stay away from that.

In general, I haven't found my HRM useful for estimating calories burned hiking. Actually, the only thing I use my HRM for is for cardio training at moderate and high intensity, and then I'm using it to just monitor to my heart rate.