Re: @ Version 1.0 ... heart rate measurement
"When exercising the max heart rate is a formula... 220 minus your age."
I would go so far as saying that anyone who uses this particular formula doesn't care at all about their HRMax. (it only applies to 80% of the populace anyway - the rest can get stuffed)
The proper way of doing it requires a warmup, then to work as hard as you can while monitoring your HR using a device that isn't a piece of shit like the Fitbits.