At a Wales training camp this month, the 17-cap wing clocked 1.56 seconds for the 10-metre dash, 0.29 seconds faster than Bolt's world record run at the Beijing Olympics.
Now he aims to keep Wales on the front foot in the Autumn Tests starting against the Wallabies on November 6.
"I'm the fastest I've ever been, the heaviest and probably the leanest, so I'm really happy with the way things are going in the gym," said Halfpenny.
"I've been working hard on my speed and footwork and now I want to show it on the pitch."
Halfpenny will get that chance at Stade Pierre Antoine as Cardiff Blues take on Castres in the second round of the Heineken Cup tonight. And with Gatland due to name his autumn squad next week, it's a final chance for players to impress the former All Black.
"I'm really looking forward to the autumn internationals," continued Halfpenny.
"There's nothing better than playing against the top three teams in the world and I'm looking forward to getting stuck into them.
"If we can get some results our confidence will go through the roof.
"But the Blues are my focus right now. It's always hostile in France and the fans try to put you off your game. But that won't affect me. I don't think it can get any more hostile than the Amlin Cup final against Toulon last year in Marseille and we won that game.
"French teams are always strong but we're confident. We've won in France before and we can do it again. I'm looking forward to going out there and doing whatever it takes to get the win."