Originally Posted by krazyderek
i had a 280 hr once, after a 20km/h (treadmill) sprint, measured it by hand so it's real, funny thing is i think it actually increased once i realised how dangerously high it was lol
280 would be very hard to count and it is easily mis-estimated if using a short (e.g. 5 second) interval because of start/stop bias errors; 12 or 15 seconds is a more reliable interval. Although my max now has really fallen down (160s typically), when I was running/racing I did get high rates in one workout in particular: 3 x 3000m (1.86mi) on a rolling course, with 10min jogging in between, run at 10,000 "goal pace". I got 200-210 after the first, 210-215 after the second and 225-235 after the third.