Superstar determined to continue honing championship form ahead of next year's Tokyo Olympics

Any fears that a recent doping controversy might upset Sun Yang's winning rhythm were quashed at last week's national swimming championships in Qingdao, Shandong province.

In January, a British newspaper alleged the three-time Olympic gold medalist had deliberately destroyed one of his blood samples, with the case morphing into a drawn out and messy legal wrangle.

But if the dispute was weighing on Sun, he certainly didn't show it and looked in fine fettle as he revved up his preparations for July's World Aquatics Championships in Gwangju, South Korea, and next year's Olympics in Tokyo.

Sun showed he's still Team China's alpha male by completing a grueling freestyle schedule on Sunday with victory in the 1500m final in 14 minutes, 55.00 seconds, adding to the 200m (1:45.73), 400m (3:43.73) and 800m (7:48.03) titles he collected earlier in the week.

"I have to better prepare myself by building my strength," said Sun.

"I will face a similar tight schedule at the world championships, which require great body strength as the foundation of a championship performance.

"I had to treat the national championships exactly like the world championships, pushing myself in each race."

Sun's return to dominance is a welcome relief for Team China.

In January, The Sunday Times reported the 27-year-old had destroyed a sealed blood sample during a visit to his home by a doping official last September.

The Chinese Swimming Association blamed Sun's non-compliance on the testers' failure to provide official identification－which sparked a series of challenges and allegations from both sides.

The International Swimming Federation (FINA) ultimately ruled the test was invalid and cleared Sun of any wrongdoing.

However, according to Associated Press, the case is headed for the Court of Arbitration for Sport after the World Anti-Doping Agency appealed FINA's ruling.

At the nationals, the affair seemed far from Sun's thoughts.

"Winning the 1500m was my happiest moment at this year's national championships," he said. "Competing on the last day meant my body strength was not as good as on the first day.

"Fifteen minutes is a barrier. I'm more confident now before I start the next phase of preparation. The capability that I've shown in the 1500m race will also benefit my 400 and 800 races.

"For me to compete on the final day is hard enough. The 1500 is so difficult, both in terms of training and competing.

"Fewer swimmers dedicate themselves to long-distance races. I consider them a challenge to have more solid preparation. Tougher training is what I want."

Sun's coaches weren't so sure that was a good idea and suggested he drop the 1500, but their plea fell on deaf ears.

"The 1500 is where I started my career and I could not just give it up," he said.

"I will just treat it as training, although it's extremely challenging."

Despite the unwelcome headlines, the megastar has maintained his punishing daily routine of training and recovery－even during Spring Festival in February.

That unerring dedication has impressed his coach, Zhu Zhigen.

"Sun reached the goal we set," Zhu said after the nationals.

"Through the winter training, especially in Singapore, he sharpened his skills and built better body strength.

"Our priority is the 2020 Tokyo Olympics. There's still more than a year for us to prepare. For veterans like Sun, they should focus on refining their skills.

"The 1500m race is just like the marathon of athletics, which requires a strong will.

"After winning the 1500m gold at the 2012 London Olympics, Sun's mentality has changed. Now he has returned to the hardest challenge, so he must stay strong."

Sun's legacy loomed large at the nationals, with 100m freestyle champion He Junyi among a number of young guns to pay tribute to their hero.

"Sun Yang has been my idol ever since I was a kid," said 22-year-old He.

"After I worked with coach Zhu, I saw how hard he tries every day. He will always be my role model."