Michael Phelps, already the most successful Olympian of all time, picked up his third successive world 100 meters butterfly title on Saturday.
The American clocked 50.71 seconds to clinch his third gold of the championships in Shanghai and then said he could only get better ahead of next year's London Games.
"The 50.71 is okay for now but there's a lot of improvement to make before London," said Phelps who is using the championships to gauge what he needs to do to prepare for his final Games before retirement.
"I'm not in the right shape physically, I want to be faster. I will watch some races and think about how I can be faster," he told reporters.
"It shows I'm going in the right direction and making progress ... this is going to be a lot of help that I can work on next year," added Phelps who landed an unprecedented eight golds at the 2008 Beijing Olympics.
Teenager Melissa Franklin, on her debut at the championships, almost stole the spotlight from Phelps when she won two golds in different disciplines.
The 16-year-old claimed her first title in the 200 backstroke and then swam the freestyle leg as United States lifted the 4x100 medley relay gold.
It was the first time the U.S. had won the medley relay since 1998. China finished second and Olympic champions Australia took bronze in the final race of the day.
"It's unbelievable," said an excited Franklin. "I'm really happy."
Olympic champion Rebecca Adlington also showed she was heading in the right direction ahead of the London Games with a thrilling finish in the 800 freestyle final.
The Briton, who took silver behind Federica Pellegrini in the 400 freestyle last weekend, battled with 2009 Rome world champion Lotte Friis stroke for stroke before piping the Dane on Saturday.
Friis led on virtually each lap. Adlington made her move at the halfway mark before her rival surged again to move in front for the next 300 meters.
The Briton, trailing by half a body length with 50 meters to swim and roared on by the home crowd, then turned on the after-burners to win her first world crown.
"Lotte is amazing. She is always tough and I just focused on my swim and put my head down," Adlington said. "It was a very tough race.
"Everybody is excited now for next year. It can be more pressure now (but) I welcome that."
Brazil's Olympic champion Cesar Cielo put the specter of a possible doping ban well and truly behind him when he retained his 50 freestyle world title.
The 24-year-old, who also won the 50 butterfly on Monday, was cleared to compete just three days before the championships when the Court of Arbitration for Sport ruled he had taken "sufficient precautions" in handling his supplements.
Cielo had said the supplements were contaminated and were the cause of a positive test for the banned diuretic furosemide.
"I was tense during the entire week. But I'm satisfied with the way I overcame everything. That shows a lot of mental control," Cielo said.
"It's great to be world champion, it's great to defend my title. I feel on top of the world."
Dutchwoman Inge Dekker was first in the women's 50 butterfly, edging out world record holder Therese Alshammar of Sweden.
"The 50 meters is always exciting," said Dekker. "Anyone can win it -- this time it is me."