If by tough you mean physically demanding you can't beat F1 racing. < pause while non racing fans laugh >
Think about it. It's 30 plus degrees celsius. Your wearing several layers of fireproof clothing, crammed into a tiny space and must experience 5G's plus. Under these conditions you must concentrate 100% for up to 2 hours. One tiny lapse and it's over. F1 drivers are probably the most physically fit atheletes in the world. You could argue that, but you'd be wrong.
(now if you mean tough as in beating the crap out of the other players well that's a different story)