The three-day 375km race, which includes kayaking, mountain biking, running and road biking, began in Alexandra on Saturday.
Yesterday was the toughest day, according to Pearson, as the athletes faced a 50km steep mountain bike, 24km road bike, 15km run, and a 58km mountain bike.
He said the 58km bike through the Thompson Gorge was the ''crux of the event'' and resulted in leading male Scott Cole, of Sweden, increasing his lead ''considerably''.
''Yesterday, he was second, about 3min down, but today he has increased [a lead] by about 20min.''
In the women's section, Simone Maier, of Wanaka, was ahead of her closest competitor and training partner, Alsa Rolinson, also of Wanaka, by about an hour.
The Pulse Fitness team of Jason Palmer, of Balclutha, and Alex McGregor and Blake Luff, both of Alexandra, were leading the team section by about half an hour.
The race continues today with a 42km road bike to Albert Town, a 45km kayak down the Clutha River, a 10km road bike to Earnscleugh and a 10km run to the finish line in Alexandra's Molyneux Park.
Pearson said he expected the leaders to cross the finish line about 1pm.
