It is common knowledge that optical HR seniors have poor accuracy with dynamic moments and escalating HR. We have all been hoping Apple has perfected the process a lot like they did with the Finger Print reader. However the latest post on Christy Tulington's blog may show otherwise. She says she has done 2 runs since getting back. She said she did an 8 miler and a 16 miler, plus a bootcamp session. There is a pic of her Watch with the caption "A summery of my evening run". At first glance it sounds like her 8 mile run but the time is far too short for her speed. She is not a 7:30 minute mile runner over distance since she ran 9:19 minute miles in the ½ marathon. However even for her small frame the quantity of calories burned in an hour is far too low for a run at only 298kcal (plus 72kcal resting). If she just walked an hour she should burn this many or more. Maybe this is actually from her bootcamp session which would sound more plausible but still low. Not sure what to make of all the discrepancies but the calorie count for time is low and may indicate inaccuracies in the HR sensor.