Burpees. It sounds like something you associate more with belching or how a child might cheekily phrase the human reflex.

But for a group of Core Four fitness enthusiasts it signifies the hardest challenge in the group's four year existence – both mentally and physically.

Core Four member Kim Hawke and founder Mike Minnell prepare to burpee broad jump 2km up Mauao. Photo: Bruce Barnard.

From 6am tomorrow members will attempt to burpee broad jump from the base of Mauao to the top along the 4WD track – just over 2km in total.

A full body exercise, the burpee sees people drop into a squat position with their hands on the ground, kick their feet back, while keeping arms extended, immediately return their feet to the squat position, and then jump up from the squat position.

In this instance the burpee is followed by a stationary two footed distance jump, and then repeated.

Core Four founder Mike Minnell says the challenge now only is about pushing yourself to the limit, but keeping active as a fitness group all year round.

And while they like to push the boundaries when it comes to such challenges, this is the 'most extreme” challenge conjured up, concedes Mike.

Previously they have hosted the annual Burpee Mile at the Tauranga Domain for the last three years along with various challenges including running to the top of Mauao with sandbags and lengthy sessions at The Gym Tauranga.

'This time we thought we would step it up and do something a bit different and a bit more extreme. We are trying to look into it and see if anyone else has done this and we don't think so, so it could be a first.

'We are probably going to have to do double the amount of burpees as we are going uphill.”

At this stage about six people are signed up to take on the challenge, but anyone is free to join in, whether it is taking part for a portion, or offering vital encouragement during the physical and mental slog, says Mike.

No time frame has been estimated on completing the challenge, and though it's not a race by any means it might pay not to burst out of the blocks too early on.

'If your mate's falling behind, you go back and support him rather than heading on in front."

The group will start its ascent at 6am from the start of the 4WD drive track.