With the global swimming spotlight focused on the July 14-30 FINA World Championships in Budapest, Hungary, China's Sun Yang is concentrating on a more minute goal.

The 25-year-old, who has won Olympic gold medals in the 200-, 400- and 1,500m freestyle, is tweaking his start technique to gain a tiny but critical edge in speed.

Nearly a perfect swimmer in terms of stroke efficiency and distance endurance, Sun realized his relatively slow starting procedure - off the block to first stroke - could be fine-tuned for greater performance.

"I am used to entering the water slowly and trying to catch up from behind over the first half of the course. It's a waste of strength. If I can just start as quickly as most of my opponents, I sure could swim faster and finish strong," Sun said in a recent China Central Television interview.

If the new technique works as well as Sun expects, the tiny improvement within an already small margin of less than a second could help him maintain dominance in the 200m and 400m, and perhaps make him a decent sprint candidate for the 100m.

At the April National Championships, which served as a trial for the worlds, Sun won all five freestyle events, from 100m to 1,500m, demonstrating his astonishing potential at all distances. His times of 1:44.91 in the 200 and 3:42.16 in the 400 are the world's best marks so far this year.

Still, Sun won't push too hard in Budapest as he signed up to compete in four individual events, expecting to defend his titles in the 400 and 800 while trying to win the 200 for the first time at the worlds.

"Hopefully, the small change will play a huge role at the world championships. I am in great shape and pretty confident now," said Sun, who has been training with Australian coach Denis Cotterell in Hong Kong since returning from an intense camp in Brisbane in late June.

Sun will meet tough challenges from Mack Horton of Australia and South Korea's veteran Park Tae-Hwan in the 400, and from Italian distance swimmer Gregorio Paltrinieri, winner of 1,500 in Rio, in the longer events.

Together with Sun's former Chinese mentor Zhu Zhigen, Cotterell helped the Zhejiang native surprise the world in 2012 by winning the 400 and 1,500 at the London Olympics, making him China's first male swimmer to capture Olympic gold.

Sun has since dominated middle and long-distance freestyle, highlighted by five titles he won from 400 to 1,500 at the worlds in 2013 and 2015.

At the 2016 Rio Olympics, Sun won the 200 for the first time at a major event and finished second to Horton in the 400 final.

With the International Olympics Committee adding the 800m freestyle to the men's program at Tokyo 2020, Sun is motivated to try to become the first swimmer to win four Olympic disciplines from 200 to 1,500m.

"That's a huge motivation. It will be of great significance if I can win the 800m at its Olympic debut in Tokyo," said Sun.

"The adjustment of my starting technique is part of my preparation for that higher goal. I hope I can test it at big events like the worlds and then hone it to perfection with more intensity in training leading up to Tokyo.

"It's good timing at the start of another Olympic circle to make changes for something bigger in the future."

sunxiaochen@chinadaily.com.cn