Vivian Cheng (Wellington) will use the Great Naseby Water Race 50km event today as a warm-up for an ultra-distance international.
She is one of three women selected to represent New Zealand in the 24-hour race at the inaugural Commonwealth ultra-distance championship in England in September.
Cheng is competing in the open women's section of the race, and her her main opposition is expected to come from Dunedin police constable Aimee Manning (nee Connor), who set the open women's record of 5hr 46min two years ago. An experienced ultra-distance runner, Cheng ran 162.4km in a 24-hour race last year.
She came first in the women's section of the last two Taupo 100km races.
There are 12 runners entered in the 50km event at the third annual ultra-distance race at Naseby.
Experienced ultra-marathon runner Rudi Keggenhoff (Germany) is the favourite in the masters men over-35 grade, while Jamie Sinclair (Dunedin) and Brian Pascoe (Dunedin) are expected to clash in the men's over-50 grade.
Sinclair (54) finished 19th in the Tahoe International 100-mile (161km) race in the United States in July.
He clocked 25hr 59min 50sec to finish second of 112 starters in the over-50 age group.
Pascoe won the over-50 section of the race last year in an age-group record of 3hr 57min 33sec.
There are 13 runners entered in the 100km race, with the favourites being Grant Bowers (Blenheim) in the masters men over-35 grade, Nathan Harris (Dunedin) in the open men's section and Dunedin doctor Helen Chignall in the masters women's over-35 grade.
There are only two competitors in the 80km race and five teams in the 60km two-person teams race.
The Great Naseby Water Race
Race records
100km, men: John Bayne (Dunedin) 9hr 37min 55sec (2008); women: Lisa Nicholl (Rangiora) 11hr 53min 35sec (2008).
80km, men: Morgan Garandel (France) 7hr 29min (2007); women: Marzanne Burger (South Africa) 8hr 41min (2007).
50km, men: Adrian Bailey (Wales) 3hr 41min 26sec (2008); women: Amie Connor (Dunedin) 5hr 46min (2007).
The starting times are: 100km, 6am; 80km, 9am; 60km team, 10am; 50km, 10am.
