New Zealand's premier mountain running event, the FreshChoice Kepler Challenge, celebrates its 30th anniversary this Saturday, with several of the top runners in recent years returning to Te Anau to tackle the Great Walk in a single day alongside a host of ambitious first-timers.

They'll head capacity fields taking on the full 60km Kepler Track course and its gut-busting younger brother, the 27km Luxmore Grunt, from the lake control structure to the Luxmore Hut and back again.

The men's race record of 4:33:37 was set by Martin Dent in 2013. Zelah Morrall hold's the women's record of 05:23:34, set in 2003. 

Neither of them are in this year's line-up but there are plenty of willing contenders for their crowns including last year's men's winner Sam McCutcheon, of Wellington, and runner up Vajin Armstrong (Christchurch) who has clocked up three wins and two second places in his five Kepler finishes.

Last year's third placed Dominic Channon (Hawea), fourth-placed Andrius Ramonas (Lithuania), fifth-placed Robert Rawles (New Plymouth) and seventh-placed James Kuegler (Auckland) are all back, and there are several first-timers also predicting finish times close to the five-hour mark.

Hometown hero Dwight Grieve is aiming to improve on his personal best time of 5 hours 29 minutes in this, his eighth Kepler Challenge. The Te Anau-based police officer has completed about 12 ultra marathons and is a New Zealand Championship masters medal holder from 800m through to NZ mountain running champs.

In the women's field, look out for the return of Ruby Muir, who won in 2013, 2014 and 2015 and has a personal best time of 5:22. Last year's third placegetter Emma Perron is back for her second Kepler Challenge, but, again, there are also several newcomers from all over the world, hoping for sub-six-hour times. Among them is former Australian track champion Margie Campbell, now of Auckland, who has been making the transition to trail running, and American Britta Clark, currently in New Zealand on a Fullbright Fellowship studying environmental philosophy at Otago University, who is a former cross country skier who transitioned to running after graduating.

In the Luxmore Grunt, Etienne Blumstein-Jones, of Australia, who finished third in this year's Australian Mountain Running Champs, is targeting a two-hour finish which, if successful, would go close to Phil Costley's 2008 record of 1:52:30. Also hoping to go under two hours is last year's second place-getter Jonah Smith, of Dunedin, who has a personal best time of 1:55.

Queenstown's Sarah Douglas is back to defend her 2016 Luxmore Grunt title (PB 2:18) but expect close competition from the likes of Imogene Scott (Auckland), Tania Williams (Christchurch) and Sharon Lequeux (Dunedin).

Don't forget to also cheer for the unseen winners of the day — the tribe of volunteers who enable this great event to be held year after year.