Name: Real Time Fitness Calculation
Rating: 5 (11 reviews)
Author: DougMarsh

Near real time calculation of how fast you'd be running (or powering a bike) at 60% heart rate reserve (in kph or W), based on current speed (or power), current HR and resting and max HRs in user profile. This number should fall over longer or harder activities as your ability to maintain pace or power drops and the activity average should reflect fitness changes over the long term. Includes some compensation for gradient but not for terrain or weather. Takes 1-3 minutes to produce a value from start depending on how quickly stable pace and heartrate values are reported by the device.  Saves data into stats, laps (depending on device software) and charts tab, including cardiac drift if activity is longer than 30 minutes. This calculation probably works best on devices with altimeters and accurate heart rate monitors. Also estimates heart rate change kinetics as of v2.1 which may change in interesting ways with fitness.