So far this season, Alan has won three XTERRA World Series events from three starts and Slack has two wins from three starts.
"XTERRA Rotorua is one of my favourite stops on the XTERRA World Championship Tour. New Zealand, and Rotorua especially, has some of the best mountainbiking in the world.
"I love riding my bike through the redwood forest and stopping by the local dairy for some hokey pokey ice cream."
Both Alan and Slack will have tough fields to compete against.
In the women's field, both second and third placegetters from last year's event, Annika Smail and Elizabeth Orchard, are returning to contest the number one spot.
Slack is excited about lining up against her old rivals again. "The setting around the Blue Lake is absolutely stunning and the mountainbiking is out of this world."
The Paymark XTERRA Rotorua Festival is one of the world's biggest multisport events and is part of the XTERRA Global Tour, which hosts events in 17 countries. It offers an individual and team triathlon, and a 5.5km, 11km or 21km run or walk as well as a 26km mountainbike.