'It's actually pulled up fine. Probably a week and a half ago if you asked me the same question it was a bit stiff and sore, still,' Marsh was quoted as saying by newspapers here.
Marsh has been included in the 13-man Australian squad for the opening Test against India starting 26 December at the Melbourne Cricket Ground.
'...I've worked very hard in the last week and a half to get myself in this position and the last two or three days have been really good. I've had extended net practice and have felt fine,' he said.
Marsh's injury flared up during Australia's tour of South Africa last month and the batsman recalled how he was not able to even get out of the bed on his own due to it.
'The night that I did it I had Michael Beer and (Michael) Hussey and Alex Kountouris picking me up and taking me to the toilet,' he said.
'It wasn't pleasant. I couldn't move. Every time I did move I was struggling. I couldn't get out of bed. It was tough there for a few days. It was a tough month for me to try and overcome it. In previous times I could move around and do things by myself, still in pain, but I've never had help before to get out of bed,' he recalled.
Marsh gave details of how his back would let him down every time he tried to increase his training while recovering but things improved eventually.
'It was pretty slow at the start. I was struggling a fair bit for the first month. Every time I tried to increase my training schedule or load I just couldn't do it, I would pull up terrible.
'I've worked hard with my people back home in Perth and with Alex Kountouris, changed a few things around in the last three weeks which have helped a lot. It has improved a lot in the last week and a bit. I'm confident but we'll have to wait and see,' he said.
Marsh averages 56 in three Tests that he has played so far, including a hundred. The 28-year-old is expected to take the number three slot in the batting order against India if he manages to prove his fitness.