Heart Rate Zones are calculated on the basis of age. The
estimated maximum heart rate is calculated as 220 - the age of the user.
The peak heart rate zone is 85
cardio heart rate zone is between 70 and 84
heart rate zone is between 50 and 69
Usage
get_hr_zones(person)
Arguments
person
An instance of the Person class
Value
Returns a list with 3 vectors of length 2: peak, cardio, and fat_burn