If you were to draw, in a non-scientific way, a line down the center of Africa you would find that athletes who excel in the explosive events — 100-m to 400-m sprints, hurdles, long jump — come from west of the meridian while endurance athletes — marathoners, 1,500-m to 10,000-m runners, steeplechasers — are born to the east. Of the great athletes born in the east — and there have been many from Ethiopia and South Africa — it is the Kenyans whose record is outstanding. Between 1964 and 1996 they won 33 Olympic medals, including nine gold. Over the past 14 years they have provided 67% of medalists in world cross-country championships. The curious thing is that this remarkable talent is not distributed evenly. Just one tiny area, Nandi, the home of the Kalenjin people, with 20% of the population, has provided 72% of Kenya's top runners. Of those 33 Olympic medals, 26 — eight of them gold — went to Kalenjins. Kip Keino, Olympic gold medalist in 1968 and 1972 is Kalenjin, as is Paul Tergat, five times winner of the World Cross Country Championships. So is Noah Ngeny. And Moses Kiptanui. And Bernard Barmasai ...Professor Mike Lambert, of the Sports Science Institute of South Africa, has been studying the performances of elite African runners for 10 years. Noting the astonishing success the Kalenjin have achieved and the tiny area that has produced it he says "The odds against this happening are almost unacceptably high, and no country comes close to it." Lambert found that the Kalenjin tend to be shorter and lighter than comparable European athletes, they are able to run at maximum oxygen consumption for longer, at lower body temperatures and with greater recovery and elasticity in their muscles. "We believe their muscles better absorb the force of running," he told a meeting of London's Royal Society of Medicine in April, "and are able to translate that force into useful energy. That tiny change in efficiency makes an enormous difference." Then he looked at the Kalenjin lifestyle, which conforms to the popular stereotype of endurance athletes living in mountainous regions. Lambert points out that people from other high-altitude backgrounds, like Nepal or Peru, do not produce world-class runners. While recognizing that young Kenyans aspire to being world cross-country champion in the way that American kids dream of becoming basketball stars, Lambert thinks this is not the whole explanation. He has noted another factor: Kalenjin runners are nine times more likely than Kalenjin non-athletes to be related to world-class racers. At one Nandi school, St Patrick's High in the town of Eldoret, 72% of boys who are good runners are related to elite athletes. Lambert believes that "there is a genetic predisposition of families in the region to distance running." So now the question is how the genetic predispostion has come about. Observers have put forward ideas that range from traditional Kalenjin methods of cattle herding in their mountainous home, to mental toughness engendered by cultural acceptance of physical pain. Later this year Lambert and a group of Finnish researchers will be doing further work on the physiological aspects of Kalenjin ability.The rest of us only want to sit back and admire it.By SIMON ROBINSON NairobiThough they have now won 27 gold medals in the Olympics and World Championships over every distance from 800 m to the marathon, Kenya's male athletes won just one event at the World titles in Spain last year, and lost the 5,000-m title for the first time since 1987. Is this decline because they spend too much of the year running on the demanding European circuit? "Agents want their athletes running every week," says Kipchogo Keino, president of Kenya's Olympic committee, and winner of the 1,500 m at the 1968 Mexico Olympics. "But if you run every week you will exhaust yourself, mentally and physically." In April, Keino met members of the Kenya Amateur Athletics Association and agents representing high-profile Kenyan runners to thrash out a program in the lead-up to Sydney. He argued that athletes who make the Olympic team should remain in Kenya and train together to "build a unified team full of spirit." Runners were loath to miss out on prize money. A compromise allows selected athletes to run in Europe's Golden League events; the rest will stay home. Kenya's coach John Velzian, who is also the International Amateur Athletic Federation's development director for English-speaking Africa, says it's a matter of balance: "The trick is keeping the runners on the boil without boiling them dry."