started 2010 at 22.
But the 29-year-old said he was in his best shape since 2005 and believes he can again climb the rankings.
Speaking on Friday as he prepared to partner Alicia Molik in the mixed teams Hopman Cup in the run-up to January's Australian Open, Hewitt said he had enjoyed a rare incident-free off-season and had worked hard.
"Yeah it's been good, I've had no interruptions this year," he said.
"When you're training extremely hard, sometimes you get little niggles throughout and you've got to have a couple of days off here and there.
"This year there's been none of that. I've been at least six days a week, sometimes seven days a week, going as hard as I can.
"Personally I don't feel there's probably anybody else out there who has trained as hard as I have for the last two months.
"Where my body's at for a 29-year-old, I feel pretty good."
A typically feisty Hewitt, who enjoyed a rare win over Roger Federer in 2010 but also suffered from hip, hand and knee problems, said he would keep his training regime under wraps.
"I'm not going to let everybody know what I've been doing," he said.
"There's a few different things I've been doing out there, I've mixed it up a lot.
"The last week and a half I've been able to taper off and do a lot more quick, reaction stuff," he added.
"It isn't quite as grinding on your body physically and mentally but believe me, the first five or six weeks were bloody tough."
Hewitt, who is now working with legendary Australian coach Tony Roche, said there was a simple reason for his continued dedication.
"Because I still think I can get better," he said when asked about his motivation.
"As long as the motivation's there and I want to go out there and compete and become a better player then I'll do it."
Hewitt and Molik play the Belgian pairing of Ruben Bemelmans and Justine Henin in the Hopman Cup tournament opener on Saturday.