I shall post this here, as I ride flat pedals and have received ribbing here for using them. On this video, they found there was a difference. Rider PE was 15 (flats) vs 13 at the end of a 10 min test. HR was higher on the flats (180 vs 175), but blood lactate was the same (3.1) and gas exchange was 51 mls per kg per min vs 53. So he was more efficient on the flats. Let the trolling begin.