RENE Kalmer qualified for the World Championship when she finished fifth in her first international marathon in Prague yesterday.

Kalmer was with the leaders until 25km, but a leg injury she picked up in training on Tuesday left her trailing in the latter stages of the race and she crossed the line in 2:34,47.

In hot conditions, the halfway mark was passed in 1:13,18 and Kalmer thought she was on course for a sub-2:30 time. She would have become only the fourth South African woman to break the mark.

Kalmer, 30, won the Soweto Marathon on debut in 2009 but did not train specifically for that race and used it as a long training session.

"For me, Prague was my first real marathon, as I trained hard for it and I raced it," she said.

Kalmer tumbled on Tuesday while training at Ruimsig Stadium when a training partner cut in front of her and she crashed to the ground.

She thought the physio and resting until yesterday's marathon would have sorted out the niggle, but she started feeling some pain after 25km and lost contact with the leaders.

"I have mixed emotions," she said.

"I did not know if I should finish or not; the pain was so intense and I was hoping for a sub-2:30."

Kalmer became the third South African woman to qualify in the marathon for the World Championships in Daegu, South Korea in August.

Tanith Maxwell ran 2:32,33 in Berlin in September 2010 and Annerien van Skalkwyk clocked 2:35,32 in Singapore in December.

The trio will form South Africa's women's team for the Marathon World Cup that is held in conjunction with the global championships.