NEW YORK -- Dathan Ritzenhein, a member of the U.S. Olympic marathon team, withdrew from the Healthy Kidney 10K on May 17 because of health problems.

Ritzenhein, a national champion for the University of Colorado in 2003, suffered a quadriceps injury in January.

Even so, he won the USA Cross Country Championships that month.

Ritzenhein later hurt his foot and hamstring, and developed anemia after spending six months on anti-inflammatory medication.

Ritzenhein is the defending champion of the Healthy Kidney 10K, and course record-holder.

He withdrew from another race in Central Park, the U.S. men's 8-kilometer championship, in March because of the foot injury.

"Knowing that it might set back my preparation (for Beijing), it was with regret that we made the decision to withdraw," Ritzenhein said Thursday.

Ritzenhein expects to build up to his full level of training by early June. He believes that will give him time to prepare for the Olympic marathon Aug. 24.

Ritzenhein's promising career has often been derailed by injuries. He made the 2004 Olympics in the 10,000 meters, but was unable to finish because of calcium deposits in his foot.