Apple Watch will be presenting incorrect heart reading, pointing users

Montenegro - Although it is not yet a defect recognized by Apple, several users have seen incorrect heart readings during heavier workouts; A topic with over 3000 views in the forum of the Apple Support Communities has received more than 17 responses and generated another about the same problem in reddit.

In the description of the problem, Apple Watch seems to incorrectly record the heartbeat during P90X or Crossfit workouts, and other exercises suggested by Apple's own app exercise, including walking and jogging. The incorrect records seem to indicate beats far below normal, ranging between 60 and 80 bpm when they should be recording something above 140.

Incorrect readings (which remained even after some users have changed their watches under warranty) were proven when compared to those obtained in other operating modes that use the measurement technology through electrodes, with the result being extremely incorrect in Apple gadget, which calculates the beats per minute analyzing the blood flow pulse through a process called photoplethysmography, which apparently has some limitations as, for example, a proper functioning in people who have tattoo this area.

According to Apple's own website, different types of motion may disrupt the reading of the heartbeat, for example, cyclical movements during the race, or irregular movements as in boxing or tennis (which as well as speak in complaints should rely on programs specific training).
The most bizarre of all is that while Apple says on Boxing as an exercise it difficult to calculate heartbeat, this month she released a commercial about Apple Watch demonstrated their workout control skills just with a boxer :

Yet there is no clear explanation for what is happening with the Apple Watch, but it is speculated that the blame for this are anatomical variations, for example, some users have found that putting the clock on the forearm, near the elbow, gives results one little more accurate (something not recommended, after all, the device is designed to be worn on the wrist). The apple has not commented officially on this issue.