Inconsitenct calorie burn counts runtastic and Omron HRM

aneedell

[Sorry for the typo in the title]

Just got an Omron HR210 wrist HRM. Have been using runtastic to track "brisk" walking for a month or so. Both know my age, weight and gender. Just finished a 4 mi. walk at just under 4 mph. The runtastic app (which uses GPS for speed, distance and elevation) shows 376 Kcal. The HRM shows a whopping 830 Kcal. I may not be in as good cadio shape as runtastic assumes in that my HR (which I record by finger touch better than every 10 min or so) averages about 133 and went up to 154 on an extended uphill stretch. Any idea which to believe and what to use in MFP diary? (The runtastic figure is entered automatically (although its easy to change).

Some thoughts. Based on experience with continuous HRM readings on the elliptical I use in the office gym, I am quite confident that the HR measurements are reliable. Readings are quite consistent with the elliptical readings at comparable levels of effort. On the other hand, I've been rigorously following the MFP program for a month and a half, recording the runtastic values. My weight loss is a bit ahead of schedule (losing 1 lb every 5.5 days instead of every 7), but its not as though I've been drastically undercounting kcal for every long walk (and there have been a lot of them).

I don't really need absolute precision, but it would be good to understand what each of my devices is telling me. Does the HRM combine normal base metabolism calorie consumption with exercise? Would that be enough to explain the difference? Or is the Omron algorithm (or runtastic's) just off for someone my age and condition level.