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Children are unleashing their inner army commando or rugby player on the Bay of Plenty Polytechnic fields this morning, as they come together to sweat it out for the annual Kids Grinder.

Children tackle the obstacle courses at Bay of Plenty Ploytechnic this morning. Photos by: Cameron Avery.

More than 250 children are expected to run, crawl, jump and climb their way through the 1km obstacle course in the fifth annual event hosted by BOP Polytechnic's Aquatic and Fitness team.

BOP Polytechnic aquatic and fitness manager Keith Martin says while competitors – aged four-12 – have a laugh and some fun, the event's about to getting out and being active.

'It's about getting the community involved and getting kids out of bed having some fun, not a huge emphasis is on winning.”

Children are tasked with a variety of obstacles including two large bouncy castles, sack races, balance beams, tackle bags, ladders, cargo nets, slalom poles and bear crawls.

In a change from last year the course is being slightly extended, for both the four-seven year and eight-12 year categories, in attempts to reduce congestion at the obstacles.

Ten-year-olds Joshua Gibson, Jared Green, Harry Miller, Carter Ormsby and Levi Zawitkoski with sister Taylor, 12, dress up in army gear for the annual event.

The younger age group will complete one lap of the course, while those aged eight-12 tackle it twice.

Keith says children and staff alike are encouraged to dress up for the activity-filled morning, to add extra spice to the event.

'This year we've asked the kids to dress up, so there will be prizes for the best-dressed kids.

'So hopefully we get some commando outfits for the cargo nets and some rugby players for the tackle bags, which should be fun.”

Each year being able to crashing into the tackle bags is a popular hit, along with the bouncy castles, but Keith says there's something for everyone.

Following the race there will be plenty of spot prizes and food along with the crowd-favourite bombing competition in the thermally-heated pool.

Jo Dawson with six-year-old Lola Warren.