Athens Olympics double gold medalist Kosuke Kitajima resumed full-scale training on Wednesday and warned Brendan Hansen he is out to reclaim the world records he lost to the American last summer.

The 22-year-old competed in the Japan collegiate championships in September but has had little time in the pool due to schoolwork and other commitments.

Kitajima will train in Australia from the middle of next month to the start of January and is next expected to race at the short-course national championships in February.