I used mine last year during time trials... I'd shift between a couple of gears that would allow me to spin in the 90s range... I don't have a heart rate moniter... I tried to keep my level of effort up, so I wasn't just spinning an easy gear. Pushing a harder gear would've burned out my legs quicker and that's the best way that I could figure out how to moniter my effort rather than paying attention specifically to my mph. And I just went by perceived heart rate level anyway...

Our course is pancake flat, the only hard thing is turning around on a narrow road.