Some Iditarod mushers rest, others push on OPHIR, Alaska, March 7 (UPI) -- The father and son Iditarod sled dog race duo of Martin and Rohn Buser pulled into Ophir, Alaska, Wednesday as other mushers took mandatory layovers in Takotna. The Anchorage Daily News reported Martin Buser, a four-time Iditarod champion from Switzerland who now lives in Big Lake, Alaska, with his 22-year-old son, pulled his dog team into Ophir at 12:19 p.m. The younger Buser arrived with his dog team at 1:34 p.m. The newspaper said it appeared the Busers were taking their required 24-hour layover there. Two other sled-dog teams, Jim Lanier and Trent Herbst, left Takotna later in the afternoon, bound for Ophir 23 miles away, without having yet taken their layovers. The Busers had reached Takotna several hours after race leader Aliy Zirkle. Thirty other mushers also had gotten to the village before the Busers. Delaying their mandatory layovers will mean the other mushers who took theirs will be catching up while the Busers rest. Another former four-time winner, Lance Mackey, had his race interrupted by a health problem with one of his huskies. Mackey said the dog collapsed and he used CPR techniques to get it breathing again. Sixty-six mushers took off from Willow, near Anchorage, Sunday afternoon on a 10-day, 975-mile epic sled-dog race to Nome. It's the 40th year for the Iditarod.