It could be the spartan living environment, or perhaps growing up in the thin air nearly 3,000 meters above sea level -- or maybe it's the influence of a legendary local coach.
Whatever its secret, a remote mountain town in Ethiopia has produced a string of world-beating distance runners.
Three-time Olympic champion Tirunesh Dibaba is the current cream of the crop. Like many from her area, she was clearly born to run.
Her elder sister Ejegayehu was an Olympic silver medalist in 2004, while younger sister Genzebe was the 2009 world junior cross country champion and a younger brother Dejene is a promising 800m runner.
"Running is for me my job, but also my source of entertainment," the 27-year-old told CNN's Human to Hero series.
"It's because of running that I am well known around the world. For me, it's the ultimate thing."
Sporting excellence flows through the family genes: Dibaba is the cousin of double Olympic 10,000m champion Derartu Tulu, while she was also inspired by another cousin -- Bekelu, who she often calls her sister, and was an international distance runner.
They all hail from Bekoji, a town of fewer than 20,000 people set high in the mountains of the Arsi province, but with a freakish record for track and field success.
"Bekoji has produced so many great athletes starting from Derartu. In Beijing, Kenenisa (Bekele) and I brought home two gold medals each," Dibaba said.
"Bekoji has strong runners. Bekoji is great and can produce even greater athletes."
It has echoes of Jamaica's Trelawny district, another rugged rural setting which has produced a string of sprint champions, including six-time Olympic gold medalist Usain Bolt.
Before Dibaba, the great Kenenisa Bekele -- a three-time Olympic champion and double world record-holder in the 5,000 and 10,000m -- was the most famous product of the area. Both were coached by Sentayehu Eshetu in their important formative years.
"Sentayehu knew that my cousin Derartu Tulu ran, he knows that my sisters ran too. That's why he encouraged me to start running and used to tell me that I would be a great runner, he knew I would be a fast runner," Dibaba said.
Success clearly breeds success -- the peak of which came at the 2008 Beijing Olympics as Dibaba and Bekele both won distance doubles -- and she believes the conveyor belt of talent will keep going.
Bekele has suffered injury problems since 2010, and he had to settle for fourth in the 10,000m at London 2012 as his younger brother Tariku chased home Britain's Mo Farah and Galen Rupp of the United States to claim a bronze medal.
Dibaba was unable to repeat her Beijing double, but became the first woman to retain an Olympic 10,000m title and took bronze in the 5,000m as Addis Ababa-born arch rival Meseret Defar won back the gold she first held in 2004.
In addition, Dibaba has won four world championship golds and has also claimed the coveted world cross country title on four occasions, beating the best that Ethiopia's great rivals Kenya could produce.
But despite her faultless pedigree, Dibaba's route to the top was not without its difficulties. She hoped to further both her education and her fledgling running career by moving to the capital of Addis Ababa, a grueling 276-kilometer trip from Bekoji
She was to live with her Bekelu and sister Ejegayehu, but missed the school registration deadline by six days.
Bekelu, recognizing her cousin's talent, instead enrolled the teenager into the sport club run by the Prison Police in Ethiopia.
Her early promise blossomed, and it was not long before Dibaba announced herself on the global stage by taking a surprise 5,000m gold at the 2003 world championships in Paris, still only 18 years of age.
At the 2004 Olympics in Athens, Dibaba was beaten into the bronze medal position in the 5000m by the more experienced Defar and Isabella Ochichi of Kenya, a defeat which rankled despite her young years.
"Our country is not like other countries. Silver and bronze in our country is no better than finishing fifth or sixth," she said.