By Philip Hersh | Aug. 08, 2016, 12:44 a.m. (ET)

Katie Ledecky poses on the podium during the medal ceremony for the women's 400-meter freestyle final on day two of the Rio 2016 Olympic Games at the Olympic Aquatics Stadium on Aug. 7, 2016 in Rio de Janeiro.


RIO DE JANEIRO - It’s a good thing Katie Ledecky thinks competing against herself is fun.

Otherwise, there would be little about racing to keep her entertained.

After only 100 meters of Sunday’s Olympic final in the 400-meter freestyle, Ledecky was a body length ahead. Just that quickly, she had reduced the race to Katie against Katie, a chase of her own world record, in which she also became triumphant.

The numbers on her winning time would be so stunning they made bronze medalist teammate Leah Smith gasp. “3:56?” Smith could be seen saying as she congratulated Ledecky in the water after the race.

Ledecky had bypassed the 3:57s entirely.

The exact time was 3 minutes, 56.46 seconds, nearly two seconds faster than the mark (3:58.37) Ledecky had set at the Pan Pacific Championships two years ago. It was the largest drop in the 400-meter world record since 1976.

This was also Ledecky’s 12th world record in three freestyle distances – 400, 800, 1,500 - over the past three years. And it met one of the goals she and coach Bruce Gemmell had set out – but never revealed until she did that tonight – after she swam the first of those world records at the 2013 world championships in Barcelona, Spain.

“I kind of always rely on him to help me set my goals, because you never know what is possible unless you hear somebody else say it,” she said.

At that time in 2013, the world record in the 400 was 3:59.15.

“The goal we set was 3:56 or better,” she said. “To see 3:56 was pretty exciting.”

It was the only way she could have made the race stirring. Despite the foregone conclusion of the outcome, the crowd roared as the scoreboard showed her progress against the world record.

“It’s really exciting to see the crowd going insane,” Smith said. “You imagine it is for you, but you know it is for Katie.

“I’ve been training with her for the last month and watching her do amazing things in practice. I knew it was coming. It was just a matter of how fast she was going to go.”

In the 400-meter freestyle, first of her three individual events at the 2016 Olympics, Ledecky came into Rio with the four fastest times in history – and eight of the top 10. No one but Ledecky has been under four minutes since 2009, and she has now done that nine times.

“I know what my best times are and I have my goals,” Ledecky said after Sunday’s prelims, when asked if it was hard competing against herself. “I’m working to get faster. That’s what I’ve been doing all year. Hopefully, it shows up this week.”

It did in Saturday’s 4x100 freestyle, when her splits justified the coaches’ decision to use her despite a 7th-place finish in the 100 at the Olympic Trials. She helped the U.S. win an unexpected silver medal.

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And it did in both the prelims and final of a 400 she won as easily as expected, beating Jazz Carlin of Great Britain (4:01.23) in the final by 4.77 seconds. That was the largest winning margin in a women’s Olympic 400 freestyle since 1956.

Smith clocked 4:01.92, as the U.S. had its first two-medal event of the six individual finals in the meet’s first days. Ledecky’s was the first U.S. swimming gold, followed 40 minutes later by the men’s sprint freestyle relay.

“First I checked my time and then I looked up and (saw Smith’s finish) and I was like, `Awesome, Leah,’” said Ledecky, ever the supportive teammate. “We’re going to sing our heads off during the national anthem.”

The 19-year-old, Stanford-bound Ledecky began the race with her usual routine. She pushed on her goggles three times to make sure they were in place, then bent at the waist and clapped her hands three times before settling onto the blocks for the start.

She was ahead of world record pace at every 50-meter interval and made the last 50 her second fastest of the night (28.92). When it was over, she punched her right hand into the air.

Ledecky had opened in the afternoon with a time, 3:58.71, that took 2.74 seconds off the Olympic record, missing her now superseded world record by just .34 seconds.

“That was the easiest it has felt going under four minutes,” she said after winning her prelim by nearly five seconds. “I think that bodes well for tonight.”

In longer swimming races, unlike track and field, it is not infrequent to see top athletes go all out in the prelims, even when they are comfortably ahead.

And while it looked as if Ledecky had pushed herself hard Sunday afternoon, the remarkable thing is that was not the case.

“I can’t speak for track and field, but we used (the prelims) to help her set her tempo for tonight,” Gemmell said. “She did it masterfully. And she did pretty much let up – or at least not overextend herself – the last 75-125 meters.”

Such control has been among the ways in which Ledecky has improved since winning an Olympic 800 gold medal in 2012 at age 15 in a U.S. record time.

“She is never going to swim a tactical race,” her brother Michael said. “She will always swim a race that maximizes what she feels she can do.”

Ledecky said Gemmell had to remind her to forget the tempo she had used in the sprint freestyle relay. Since her usual mindset is attack, attack, attack, no matter the distance, that was wise counsel.

“I just kind of backed off and kept it easy up front,” she said. “I know that’s how I swim my 400 the best so I can really be strong at the end.”

She also kept up her strength with a solid eight hours sleep after the relay, which ended just before midnight Saturday, thanks in part to logistical help from the U.S. Olympic Committee and USA Swimming.

The USOC brought one of the athletes’ favorite chefs, Dokmai Flower Nowicki, from the U.S. Olympic Training Center in Colorado Springs, Colorado. She whipped up a stir fry that a USA Swimming dietician brought to the pool.

That meant Ledecky did not have to search for food when she returned to the Olympic village, after the medal ceremony, the media obligations, warm down and a massage. That allowed her to go directly to bed at 2:45 a.m.

Sunday-to-Monday would be another long night for Ledecky, since the 400-meter victory ceremony did not take place until midnight. Monday, she has the opening two rounds of the 200-meter freestyle, the only event in which Ledecky is not an overwhelming favorite.

As promised, she sang her head off during the national anthem. Unlike four years ago, when she cried after a surprise Olympic triumph in the 800, Ledecky was dry-eyed and smiling broadly when she wasn’t singing. The way things are likely to go to here the rest of the week, someone may be inclined to think of the “Star-Spangled Banner” as Katie’s Song.

Philip Hersh, who is covering his 18th Olympic Games and was the Chicago Tribune’s Olympic specialist for 30 years, is a contributor to TeamUSA.org.