I saw something on daytime TV yesterday (I'm off until next week) they had too young couples who had devices on which monitored calorie use. It was 45 mins of exercise and 45 mins of sex. The amounts were more or less the same number- one had slightly more and one slightly less. They were 200 calories plus- so for 35 it must be less exotic sex? missionary perhaps- try different positions and it should be more effective I would guess?