Yesterday I rode 7 miles as a warm up to a local cemetery that is flat and wide open. It was clear, 48 degrees with 15 mph winds. I have a .8 mile 6 turn circuit that I ride, which simulates crit race courses, that also has a sweeping curve that is the same as a straight. Yesterday I kept my HR in mid-Z3 for the 1 hr interval workout and concentrated on being low into the wind and smooth into and out of the turns. My wife drove our car over to the site with her bike in the car and then at rode her pace during my interval. It was probably coincidence, but I was riding two laps for her one. We always seemed pass around the same spot then as the hour interval progressed she started to pick up about 30-40 meters on my pace when we passed. During my interval I did have to ramp it back in order to keep my HR within the Z3 range. I tend to get into a race mode and attack too much. In review of my power files I averaged 20.7 mph and 254 watts on the interval with an average HR of 146 bpm. During my cool down I rode with my wife at her 10.4 mph pace and isolating the segment from the workout found that it took me 53 watts to ride with her at 10.3 mph. Last night for me it took around 5 times more power to ride twice as fast as her pace. BTW, my wife had fun since it was on a closed course, she didn't mess up her hair with a helmet, and she said she got a good cardio workout.