I tried Quizlet for many months, but actually just recently switched to Anki. The Quizlet UI looks better on the surface, but Anki's UI is faster and more... utilitarian.
He says about his heart rate that it's "below 100 if I run 10 kilometers". That seems pretty amazing to me. I've been measuring my heart rate recently and mine's at about 150 bpm if I run at a medium pace.