Mathieu van der Pol suffered a crushing defeat to rival Wout van Aert in the X2O Trophy race on the sands of Coxeide on Thursday. But beyond the disappointment of missing out on the win, there were also concerns about a recurrence of the back pain that interrupted his cyclocross campaign last winter.

The Dutch rider, who has won four of the 11 cyclocross races this season, was seen standing up on the pedals and stretching his back several times during the one-hour race. He was pulled away by van Aert on the fourth lap of the race and held on to finish.

Van der Pol eventually finished 1:38 behind Van Aert and worried about recurring back pain.

"All of a sudden the pain in my back came back," Van der Pol told Belgian television station Sporza after the race.

"It sucks, but there's nothing I can do. But I can't help it. It's a shame because I was looking forward to this race."

Van der Pol has had great success in Coxsayde, winning the last five UCI World Cup races on the sandy beaches of the Belgian coastal town.

But on Thursday, back pain dashed his hopes of adding to that record, despite his good form.

"My legs were feeling pretty good too, but at one point I could barely put one foot in front of the other," van der Pol said.

"I was in pretty good shape this winter. I really don't understand where it suddenly came from."

Van der Pol did not suggest that his back problems were serious, as he missed last year's Mountain Bike World Championships, limited his participation in 1.5 cross races, and avoided road training until February.

"In the races so far we have been evenly matched. In theory, we should have continued that today," he said, referring to VanArt, who has improved to 5-3 on the season against him.

"I'm a little worried, but I'll be fine."

Van der Pol will race again this Sunday when the World Cup heads to Zonhoven. He has won three of the last five races and will compete in Benidorm later this month after attending a training camp in Alpecin-Desseunink.

"I hope to loosen up my back tomorrow so I can give it my best again on Sunday," he concluded optimistically.