I the fasted cardio with MAG-10 this morning. I started at the 4% incline and at 3 mph. I began measuring my heart rate using the monitor on the treadmill. It got up to around 130, so I dropped to 2.5 mph. Measured again and my heart rate had dropped to around 65. Upped it to 2.8 mph and my heart rate was at 120 and eventually back to 130. Moved to 2.6 and my heart rate went back to around 110. My question is, how accurate are these monitors on the treadmill? Should such minute changes in speed be causing such jumps in heart rate? Just trying to keep below 120 as the article said.