Australia's Olympic champion Steve Hooker said Wednesday he was making secret, ground-breaking changes in a bid to return to the top of pole vaulting. But Hooker, 29, fit again after an injury-riddled 18 months, said expectations of defending his Olympic crown in London next year were unwarranted. Hooker said his left knee could again cause problems, but he was working on new technical adjustments in training. "In some ways, I'm going back to square one," Hooker said in a teleconference. "I have got a good idea of what I want to do in terms of a technical model. "But just in terms of having the confidence in my body that it's not going to break down, having the confidence in my take-off, in my run-up, and feeling my rhythm on the runway, it's completely back to square one. "It's a tough process and not the ideal process to be doing at the start of an Olympic year. "But I feel like, given I'm healthy, I have got plenty of time to do it." Hooker but did not go into details, saying it was a "secret". The pole vaulter said he was putting in a lot of hard work after his injury misery. "All I want to do right now is stay healthy and jump as much as as I can, just so I have every opportunity to get back in the best shape for London," he said. "But I have also got to be aware that this is an injury that (could) come back at any time."