Long before daybreak on Thursday, hundreds of soldiers invaded Edmonton's river valley for a punishing test of strength and stamina.

The Mountain Man Challenge is an annual summer race for soldiers and reservists in the city.

At 5 a.m., the blast of a horn echoed through Hawrelak Park marking the beginning of the back-breaking race, and sent some 350 competitors on their way.

"It's tough. It's a very challenging race," said Sgt. Jonathan Pagé, a member of the 3rd battalion of Princess Patricia's Canadian Light Infantry.

"It can take up to six hours to complete, so going into it from the starting line, you know it's going to be a long, long day."

'It hurts'

The 50-kilometre course is a gruelling one.

Although it's considered a triathlon, the race has four parts: a 32 km footrace, a 3.2 km portage, a 10 km canoe race on the North Saskatchewan River, and finally another 5.6 km footrace to the finish.

And if that wasn't challenging enough, every competitor must carry an army issue rucksack with a minimum load of 15 kilograms.

"The hardest part is the portage, carrying the canoe. It's just miserable," said Pagé.

A competitor in Thursday's race departs races from the starting line in Hawrelak Park. (CBC Edmonton) "It hurts, because those canoes aren't mean to to do that. They've got a big steel bar in them that's digging into your neck, and your legs are already tired from running the 32 k so you're already hurting pretty bad.

"The trick is not to stop and keep going."

Racing rivalry

This is the 15th year for the voluntary the race which is open to all military members of 3 Canadian Division.

"It keeps us in shape," said Maj. Spence Sharpe. "It allows us to do a gut check and mental check on our ability to do this arduous tasks at a moment's notice."

Although the race is designed to push participants to their physical limit and beyond, Sharpe says members of all ages, rank and fitness levels take part every year.

"It's across the board," Sharpe said.

"A lot of people do it, they've been doing it for eight or nine years and they just keep going.

"There are the hardcore racers that like this kind of stuff. And for them it's a point of pride on who beats who, and there is the normal rivalry that goes along with that, among friends of course."