Aged only 13, Chemchumba competed at the 1992 IAAF World Cross Country Championships, finishing 27th in the junior race. Still at junior level, she participated in the 1994 and 1995 edition of IAAF World Cross Country Championships, finishing 7th and 10th respectively. At the time she took a break in running to concentrate in schooling, where she was lagging. She went to Kapkenda Secondary School in 1997.