|Ethiopian Belayneh Densimo's 2:06:50 at the Rotterdam Marathon in 1988
||American Jon Erikson, New Zealander Philip Rush, and Briton Alison Streeter have all completed triple crossings
||Hawaiian Derrick Doerner rode a 25-footer at Oahu's Waimea Bay in 1988
||Englishman Chris Boardman's hour record of 56.375 kilometers, set in September 1996
||Canadian Donovan Bailey's 9.84 at the 1996 Atlanta Olympic Games
|The faster you run, the more fuel your muscles need; at a certain point your effort outstrips your body's ability to distribute enough glycogen. And most biomechanists agree that today's elite marathoners are already working at the highest possible levels. "At this point," says David Martin,
USA Track & Field's chairman of sports science, "if somebody goes as low as 2:06, everybody's going to say that the course was short or the guy was on something."
||Even if you wanted to swim 105 miles in the world's least forgiving lap pool, one of your most basic biological needs would prevent you. "The fastest triple was about 30 hours, so maybe someone could do four," says Ted Erikson, father of Jon and himself a Channel record-holder in his day. "But
that's probably not going to happen. Beyond 35 hours or so, everybody encounters the same thing: They have to sleep."
||Humans can't paddle fast enough to keep up with the rushing wall of water that creates such a massive wave. "It felt too big," says Brock Little, believed to have caught — but not surfed — the largest wave ever, a 30-plus-foot beast at Waimea's Quiksilver Eddie Aikau Memorial.
"There was so much water moving up the face that I just kept rising. I wanted it, I got it, but there was no way I could ride it."
||As with the sub-two-hour marathon, the problem — barring a quantum leap in bike technology — is the threshold at which the body can deliver fuel. "There have been staggering improvements to the record in the last few years," says Peter Keen, the sports physiologist who serves as
Boardman's coach. "But that's attributable to technological advances, not athletic performance. We're very close to the limit of what the body can do."
||According to the research of Gideon Ariel, an internationally renowned biomechanist who's been studying elite athletes for 30 years, running at speeds above 30 miles an hour would tear muscles and could even snap bones. "Eventually there will be new human beings — taller and stronger
— who will be able to do better," Ariel admits. Of course, evolution takes a while.