I recently bought the HeartWatch App and have been tracking my heart rate during the day, at night and during my 60 min Workout App runs. I have been running for more than 20 years, so I am in excellent shape and do not have any heart related issues. I noticed on my Workout App outdoor run today, the HR reading on the Watch showed my heart rate between 190-200 for the first 10 minutes of my run. At almost exactly 10 minutes, my heart rate drops down to a more normal 150 and then slowly climbs to a peak of 165, as expected. The temperature this morning was 36 degrees, which is unusually cold for Texas. For my other two runs this week, I also saw unusual spikes at the start of my runs, but they were not as extreme and did not last as long before returning to normal. Is this a known problem with the AW HR sensor when running? Today was the first really cold day, so maybe it is also temperature related?