Is this possible? (Heart rate and cold related)

katnz17

I clocked my heartrate at work today. I spent most of the day sitting in a room that was 6 degrees celcius. My heart rate monitor recorded my average heart rate at 103 and says I burned 1239 calories (and an online calorie converter says 1391). That's almost my daily calorie restricting allowance in five hours!

My heart rate monitor is new and I'm starting to wonder if it's faulty. On at least two occasions I've caught it reading my heart rate at 215 when I'm resting and highly doubt my heart rate could even be 115 (it only read that way for a few seconds then jumped to the correct reading). It says today my highest rate was 138 (I spent a minute walking up stairs).

Is it possible I could have burnt that much? Is your heart rate slower or faster when you're cold? I've googled it and found conflicting results.