Finished up with these yesterday as part of an indoor program I attend once a week. Highest HR I've seen for many years! I could of died!!! The task was ten seconds on and ten seconds off at 100+ cadence for 1', 2', 3', 4" with easy recovery matching the interval time.
https://www.dropbox.com/s/4qcp3maehm...49.43.png?dl=0