Dual Olympic medallist Jared Tallent surprised himself as he overcame adverse conditions to record a career-fastest time in winning the Australian 50km road walk championship.

Racing in pouring rain through gathering puddles in Melbourne, the 25-year-old from Ballarat clocked 3:38.56s on Sunday -- beating his previous PB of 3:39.27 set when claiming the silver medal at the Beijing Olympics.

Second place-getter Tom Barnes (4:12.05) was left trailing more than half an hour behind.

Making the solo performance even more surprising and exciting, Tallent was competing just three days after completing an arduous altitude training regime at the Australian Institute of Sport.

"I didn't expect the time so quickly after such intense strength and base training at the altitude camp," said Tallent, who also claimed bronze in the 20km walk at the 2008 Olympics.

"We haven't really been working on speed recently so to start the summer with a personal best time gives me a lot of confidence.

"I'm looking for a medal at the next year's IAAF road walk championships in Mexico and today's result is the ideal start to what will be a tough training schedule between now and then."

Rounding out the top three was Olympian Duane Cousins who clocked 4:14.58. In the men's 20km walk NSW's Ian Rayson won in 1:29.50 from Brendon Reading (1:30.42) and Derek Mulhearn (1:39.16).

Jessica Rothwell took out the women's 20km walk in 1:34.22 from Tallent's wife Claire (1:37.47) with Victorian Kelly Ruddick third in 1:46.49. Rothwell is also eyeing world championships success next year.

"Mexico for the IAAF world race walk championships is what I'm preparing for at the moment so to start like this in tough conditions is great," Rothwell said.

"Speed training hasn't really commenced yet so I'm really happy with my time and feel confident heading into some pretty big events."

AAP