use the hr zones configured in the profile

[peregin]

instead of using the simple formula (in the current implementation):

* HR max = 220 - age (standard formula)
* zone 1 = recovery 50-60% of HR max
* zone 2 = endurance 60-70% of HR max
* zone 3 = aerobic 70-80% of HR max
* zone 4 = lactate 80-90% of HR max
* zone 5 = VO2 90-100% of HR max

[peregin]

Using the user profile data from > My Stats > Training Zones > Heart Rate Zones