People train to run a marathon for months or years, but there's one challenge that first-time runners don't always expect — jogger's nipple.

For those people who live more sedentary lives it might sound ridiculous, but watching marathons you see it everywhere: the two red dots of blood after a shirt has chaffed nipples raw.

The Manitoba Marathon on Sunday was no different. Runner after runner crossed the finish line with fresh streams of red dripping down their shirts.

Colin Shepherd didn't even realize while he raced the half-marathon that his shirt had caused him to bleed.

"I am definitely feeling a little bit sensitive," he said with a laugh. "I am probably not going to wear a shirt for the rest of the day."

Colin Shepherd says he didn't even realize he was bleeding when he crossed the finish line but now his plans were to avoid shirts for the rest of the day. (Thomas Asselin/CBC)

He usually takes precautions by wearing specific fabrics, but said the chafing can be even worse when the weather is a bit damp, like the conditions were during Sunday's run.

Kajlil Ibrahim crossed the finish line with a shirt that looked as if it was in the beginning stages of tie-dye. He said he ran a few days earlier with a shirt with a logo on it that likely contributed to the problem, but once he was in the race there wasn't much he could do.

"I noticed it quite early on and it was smaller and it was growing throughout the race and I was just like 'what can you do?'" Ibrahim said.

Kajlil Ibrahim says there wasn't much he could do to stop the pesky jogger's nipple so he had to just keep going. (Thomas Asselin/CBC)

Many runners take precautions to avoid the dreaded jogger's curse, which was even featured on an episode of The Office. Most avoid loose shirts, which move around during exercise, and some wear surgical tape or waterproof bandages. But a lot of runners just apply an anti-chafing balm.

Mike Loewen has been running for years and hadn't had it happen since his last full marathon many years ago. When he looked down on Sunday he laughed and said, "I'll go down in the annals of running goofiness."

"If I didn't know any better I'd say my wife put a safety pin through there to keep me going," he joked.