Oh, so a banal 26.2 miles doesn't sate your punish-self jones? Then kick it up a masochistic notch and give ultramarathon running a try. It's not just the distance - usually 100 kilometers, which amounts to 62.14 miles in the metric-system-ignorant corners of the world - that makes this pursuit uncommonly punishing. No, the sport's Powers That Be add complication in the form of hills, extreme weather conditions and, most blister-inducingly, rocky/sandy/mushy/icy terrains. Those who want the purest ultra challenge should set their sights on the notorious Comrades Marathon, a 56-mile slog through South Africa's Kwazulu-Natal Province. Between the temperatures and the turf, this one'll reduce you to a drooling nub, and perhaps prompt you to reapply for that berth on the Ultimate Bathtubbing circuit.