So I've conducted two weight training workouts and two outdoor runs and have come to the conclusion that for weight training (and I would imagine the same holds true for cross fit), the AW sensor cannot lock on and provide real time, consistent and accurate heart rate due to the unnatural movements of the body and constant jerking around of weights. Also, the heart rate during weight training fluctuates so much during sets and during rest that the sensor doesn't seem to have time to catch up. My heart rate was high during rest while low right after a set. I attribute the fact that the heart rate takes a moment to catch up to what my actual heart rate is due to the location of the sensor on my wrist whereas a chest strap is measuring from the chest and pulling data based of the electrodes basically at the closest source. This doesn't appear to be an issue during runs where I noticed real time, accurate readings which I attribute to the fluidity of movement, consistency of heart rate and the ability for the heart rate sensor to lock on and maintain a solid connection. Also, all the research and data Apple has done reflects the workout choices in the workout app whereas no data exists to monitor weight training or cross fit type activities. Therefore, I believe the readings during runs, cycling, stair stepper etc are more accurate. Overall calorie burn on the other hand appears to be accurate when compared to what I'm used to seeing after conducting the same workouts with my Vivo Fit and chest strap connected. However, I'm not disappointed. Chest straps have always been proven to be the most accurate for heart rate monitoring. So I plan on buying a Bluetooth heart rate monitor for when I do weight training due to the fact that I like to see my real time heart rate while I'm working out. For runs and everything else, I would trust using the AW heart rate monitor for sure. Just thought I would share my opinion for those interested in this feature.