This is the theory that Tim Young developed, as he dragged car tyres around a mud-clogged field. "It's good to find out how far you can push yourself," he said. "Very often, people are set in their mundane ways. But in this job it's useful to look outside yourself."
In six weeks' time Mr Young will step outside his own mundane ways, as head of PE at King's college private school, in south London, when he embarks on a four-week race through the Canadian Arctic Circle. Filmed for a programme to be shown on BBC2 in August, Mr Young and his two team-mates will compete against nine other teams to be the first to reach the magnetic North Pole.
Given the choice between confronting Arctic wildlife or a class of cocky teenagers, he chooses the former. "Kids are sharp and work you out quickly.
Polar bears are a bit more wary. And we'll have a gun. You can't take one into the classroom. Though it might keep the kids quiet."