Rubuta ci gaba don wannan sakin layi - Chepkok an haife shi ne a Kapkitony a Gundumar Keiyo na lardin Rift Valley na Kenya. Ya lashe lambar azurfa a tseren matasa a Gasar Cin Kofin Duniya ta 2007
, ya gama na tara a Gasar Cin Kofin Duniya ta 2009 kuma na bakwai a Gasar Cin Kofin Duniya ta 2009. Ya sami babban nasara na mita 5000 a kan layin IAAF Diamond League na 2010, ya ci nasara a gasar Grand Prix ta Burtaniya.