Associated Press Katie Ledecky took on the most grueling challenge of her swimming career and won three times. This week might be only the warm-up. The Maryland swimmer pulled away in the women’s 1,500-meter freestyle final Saturday in Indianapolis, winning in 15 minutes, 47.15 seconds, posting the fourth-fastest time in world history and shattering the one of the oldest long-course championship records in the American book. Janet Evans set the previous mark in March 1988, when she finished in 15:52.10. Twenty-five years, two months, three days later, Ledecky cut that time by nearly 5 full seconds to win another U.S. national title and give herself a chance to become the first American woman to swim the four longest freestyle events at a world championship. “I’m very happy with that time and it’s a good way to finish the meet,” Ledecky said. It can’t get much better. Ledecky competed in four races at the IUPUI Natatorium, winning national championships in the three longest events — the 400, 800 and 1,500 free — in astoundingly easy fashion. Saturday, she was under world-record pace for the first 600. Though she faded over the final 900, she still broke Evans’ mark and produced the world’s fastest time of the year. Natalie Coughlin, a 30-year-old three-time Olympian, barely won the 50 free title over a rising star nearly half her age. Coughlin finished in 24.97 seconds. Simone Manuel, 16, was second in 25.01 seconds, breaking the national age group record for the second time in one day. Nathan Adrian started the week by winning the 100 free and ended it by taking the men’s 50 free title in a race that featured five Olympians. Adrian won in 21.47 seconds. Ryan Lochte, the world record-holder in the 200 individual medley, was just 0.12 seconds off that pace after 150 meters but faded over the final 50 and settled for his third win of the week in 1:55.44.