Running

What are burpees? Google tells me they are some kind of squatting exercise, but I assume you weren't doing that, were you?

Weak google-fu you display. Burpees are a cross between a squat-thrust and a star jump (well, not everybody jumps but it's always a return to fully upright stance). Why do you assume he wasn't, when he says he was? Burpees are popular in high-intensity workouts; you can often see BMF trainers putting their groups through them in London's parks.