First, great job on being that disciplined. It’s rare, and I’m sure that it will pay off.
I’ll leave most of this for Scott and Steve to comment on, but the one thing that jumps out at me is your expectation for a max HR response. Unless I’ve misunderstood what you described, 60 seconds isn’t a long enough duration to elicit a max heart rate.
The load itself (a 60″ sprint) is certainly high enough, but that intensity won’t be able to be maintained long enough for anyone to get to a maximum HR. I don’t know what the shortest possible time would be, but my guess is somewhere in the range of 10-12′ using an effort that somewhat exceeds anaerobic threshold.
My two cents,