A year after blighting the defence of his double scull title in London, the spinal complaint continues to hamper Brennan's attempts to get back in a boat.

But as fellow rowers including girlfriend Kim Crow head to South Korea for next week's world championships the 30-year-old still believes he can make an Olympic swansong in Rio de Janeiro in 2016.

``I've never experienced anything this frustrating in my whole life,'' Brennan said.

``At the moment I can't pull the same numbers I was able to when I was about 13 years old and that's heart-breaking and very difficult not to get incredibly frustrated by.

``I was keen to have one last Olympics because I was very disappointed with how London finished so I signed up for the long haul after that.

``I believe if I stay with this then four years is enough time to retrain my body to move again.''

Brennan's desire to return to the pinnacle of his sport has seen him travel as far afield as Canada and seek the advice of another Olympic champion with back issues, Drew Ginn.

Back complaints dogged Brennan and crewmate Dave Crawshay in London where they eventually finished eighth and were forced to watch the final from the shores of Eton Dorney.

After the Games, Brennan said even breathing could be painful and he spent four months undergoing injections and treatment.

Another setback had him doubting his ability to return before Tasmania's Olympic physiotherapist Kellie Wilkie encouraged him to visit Canadian thorax specialist LJ Lee.

``That confirmed that it was going to take time but that the ability is there to return to full rowing,'' Brennan said.

``I have no knowledge of the rehabilitation process but she does and I guess part of the challenge has been to let go of my expectations for a while.

``It's a difficult process and I'm as confident as I can be. I have to reteach the way the brain uses muscles and the way my body moves and that's not something you can do quickly. It's a very long process.''

With rowing almost out of the question, the Canberra-based Lindisfarne doctor has been spending endless hours on the bike and can see the rewards.

``Since the injury, the option of rowing has been taken away from me so I'm quite motivated to get back in the boat and compete like I once did.''

Asked what boat he pictures himself returning in, he replied: ``I just picture myself rowing. I don't care what boat it is in as long as I can row.''