Fatigue in hot and humid conditions persuaded Shane Watson to take the aerial route and hit as many balls over the boundary rope as he could during his world record breaking one-day innings of 185 not out on Monday.

- Stats: Watson's world record 15 sixes, 15 fours

Watson struck 15 sixes in the second one-day international against Bangladesh to break the previous record of 12 set by West Indian Xavier Marshall three years ago against Canada.

His innings is also the highest one-day innings by an Australian, surpassing Matthew Hayden's 181 against New Zealand in 2007

"It's just one of those days where everything that you try comes out of the middle of the bat, a mishit goes into the gap or you get dropped," Watson told reporters.

"I got to a point where I got pretty tired, it was hot and humid out there so I didn't really want to have to run too much.

"I was either going to try to hit as many sixes as I could or get out because I was pretty tired, that was as simple as it was," he said.

Watson said he had not targeted Hayden's record.

"I don't know exactly how many balls Matt Hayden faced," he said.

"In the end I'm not playing to try to break records or anything like that, I'm just trying to back myself and if it comes off like it did today then it's brilliant.

"As I walked off I thought I was close to Matt Hayden. I actually played in the game and got 60 in the game Matt Hayden got 181. It's nice everything came off for me today."

Former captain Ricky Ponting, who watched from the other end during an unbroken second-wicket partnership of 170, praised his partner. Ponting was unbeaten on 37 as Australia reached their victory target from only 26 overs.

"(He) made my job easy," Ponting said. "I just had to get a single to give him the strike. No one expected it to get over that fast.

"I have been lucky to play with some great players, Watto has played some great innings...this was an amazing innings.

"Some of those sixes would have cleared any boundary in the world. It probably won't sink into us for a while how good that was."