Ai Shibata (JPN), Olympic 800m freestyle champion a touch ahead of Laure Manaudou  (FRA) in 2004, has announced her retirement alongside a footnote of burden and pain.

Years of injuries had left her body wracked with pain, said Shibata, as she waved goodbye to her sport. In Athens in 2004, she became the first Japanese woman to win an Olympic freestyle crown. She did not make the final four years on in Beijing and in a tearful statement to reporters she said: "My body was yelling out in pain. I realised I had reached my limit. My shoulder and back have been so painful since Athens."

The 26-year-old added: "The gold medal was a burden. I can't imagine myself swimming at the (London) Olympics four years from now." 

The world has already been transformed since Shibata won in Athens. The 8min 24.54 in which she triumphed, 0.42sec ahead of Manaudou, was 13th fastest all-time in 2004, when the best four times swum were held by swimmers who had already retired and women distance swimmers were finding it impossible to get down to 8:20. Shibata improved to a best of 8:23.76 by the Japan Open in 2007. That time is now 18th best all-time, while her 2004 Olympic winning time has been surpassed by 55 other performances, including 20 in fast-forward bodysuits this year alone. 

Five of the best 10 performers ever in the 800m freestyle clocked their fastest time this year. At the helm is Rebecca Adlington (GBR) with that stunner of a world record - 8:14.10.

If you trawl back year by year for the past eight years, here are the numbers of new entries in the all-time top 10 in each 12-month period:

• 2008: 5
  
• 2007: 3
  
• 2006: 1
  
• 2005: 0
  
• 2004: 1
  
• 2003: 2
  
• 2002: 1 
  
• 2001: 1
  
• 2000: 3

And in Olympic years back to 1984: 

• 1996: 0
  
• 1992: 0
  
• 1988: 4
  
• 1984: 3

 Shibata, whose brother Ryuichi is third-fastest 200m 'fly swimmer ever in Japan, was born on May 14, 1982 in Dazaifu, Fukuoka. She won the 400m and 800m events at Olympic trials in Japan this year but the writing was on the wall: her 4:10.38 in the 400m suggested that she would no longer be a contender over 800m.

A year earlier in Melbourne, she had still been good enough for bronze at the world championships. But in December 2007, she hurt her back and her training programme had to be curtailed. 

"Sometimes I recall the race when I had the world record. But at the Olympics my biggest goal is to exhibit what I can do."

Her long-term coach is Takao Tanaka, at the National Institute of Fitness and Sports in Kanoya, Kagoshima Prefecture. He taught Shibata not to cry in public no matter how disappointed she was. "Tanaka-sensei has told me that if you show your weakness before people, you may show it again later," said Shibata. "And you've got to have a strong mind." That worked well as a competitor, perhaps, but at the moment of farewell, there was, naturally enough, no holding back the tears.