Peter Greste, the Al Jazeera journalist freed after more than a year in an Egyptian prison, on Thursday (February 5) spoke about his experience behind bars.

Arriving with his parents at a news conference in his home city of Brisbane, Australia, Greste smiled as he received a warm welcome from the Australian media.

"I know from my readings, I know from my experience with other people, doing stories on other people who've been through some pretty difficult times that to get through it you need to be fit, and that's not just physically fit, it means staying mentally fit, intellectually fit and spiritually fit and so I and my colleagues made a very deliberate effort to staying physically fit. We had some pretty limited space but we made sure we worked out, that we kept ourselves healthy. I also embarked on or began a course in, a Masters degree in international relations," Greste told reporters.

He was released on Sunday (February 1) after 400 days in a Cairo jail and had been in Cyprus since then. He had been sentenced to seven years on charges that included aiding a terrorist group in a case that had attracted widespread attention and criticism of Egypt's leadership and judiciary.

Greste has sworn to continue efforts to free his Al Jazeera colleagues, Canadian-Egyptian Mohamed Fahmy and Egyptian national Baher Mohamed, who remain in prison.

He said their support had been important.

"We knew people would have their up days and their down days and we were very careful at helping one another out, listening to one another, talking to one another, supporting one another and at the same time giving space when we needed it. So I think we've all grown very close as a result of this process, as a result of this experience, but that was also very, very important to surviving it," he said.

Greste said he is not sure what he will do next but said he wants to return to journalism after spending time with his family.

He was asked what his immediate plans are.

"As they say in politics, spend time with the family. I don't quite know what's going to happen over the medium to longer term. I mean, I've only just walked out. There are so many things to think about, so many things to consider. Obviously, there are some other projects that might emerge from this whole experience that I'd like to look at but right now there are far more doors that are opening up than I've really had a chance to look through. I don't want to give this up, my job up. I'm a correspondent, it's what I do. How I do it, whether I actually do go ahead with it I don't know. That's the way I feel right now. That's my honest answer but that could easily change and exactly how and where and under what circumstances I don't know," Greste said.