A man is in a critical condition after competing in the Mud Sweat and Tears challenge in Canterbury today.

A St Johns ambulance spokesman said emergency services were called to Motukarara at 11.51am today where a man in his 60s suffered a serious medical incident.

He was flown via a Westpac rescue helicopter to Christchurch Hospital.

Fire service also attended the scene.

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The event is based at the Motukarara race course where participants are required to complete obstacles including mud slides, forest runs, hay bale pyramid, a crawl under a sea of barbed wire, horse jumps, water jumps and mud runs, the website stated.