The 31-year-old from Kamloops, B.C., competes on the first day of track and field Friday at the London Olympics, four years after he missed a medal by less than a centimetre and finished fourth at the Beijing Games.
Since then, the six-foot-four, 345-pound mountain of a man has worked his way up the international rankings, and was No. 1 in the world last year.
Canada has won two silver and five bronze so far at the Games but is still looking for its first gold. Armstrong has a shot at being the athlete who wins it, but with a stacked field it won't be easy.
Armstrong believes there are up to six throwers that could climb the top step of the podium — including Americans Christian Cantwell, Reese Hoffa and Ryan Whiting, ranked No. 1-3 in the world.
Athletics Canada head coach Alex Gardiner believes Armstrong is on pace for a strong performance.
"He's recorded a couple of workouts that have been better than any he's had in his life," Gardiner said. "When I heard from him three days ago that he had a personal best in one of his training sessions, I know that he's ready. And he's honest as the day is long."
Armstrong, who's been training in Portugal since the Olympic trials last month in Calgary, has battled back from an elbow injury that kept him out of the final at the world indoor championships. He goes into the event with the eighth-best throw in the world this year — 21.50 metres. His Canadian record, set last year, is 22.21.
"He's ready, he's healthy," Gardiner said. "The elbow problem he had is gone. He's protecting his energy right now."
Nine Canadians compete on the first day of track and field including Jessica Zelinka of London, Ont., who is gunning for a podium finish in the heptathlon after finishing fifth four years ago in Beijing.
Most of the team arrived in one piece from a camp in Kommen, Germany.
"Coming out of Kommen, I would say we're pretty close to 100 per cent injury-free. Unusual for track and field," Gardiner said. "This our 12 days of the Olympics. (Saturday) I'm hoping for more than a partridge in a pear tree. I think it's going to be a good day."
Canada also has medal chances on the first day of trampoline as Jason Burnett performs his daredevil routine.
Burnett won silver in Beijing with the highest degree of difficulty in the men's field at 16.8.
The Nobleton, Ont., athlete has upped the ante for London. Burnett's preliminary routine Friday has a degree of difficulty of 17.6. If he makes the final, it will be 18.2.
Canada's women's soccer team plays for its first-ever spot in the final four when they battle Britain in Coventry.
The night won't be an easy one for the seventh-ranked Canadians. Britain has been one of the surprises of the tournament, winning all three of its preliminary-round games and is the only team that hasn't conceded a goal.
The Brits will have the crowd on their side too. Their 1-0 victory over Brazil drew 70,584 fans to Wembley Stadium, a British women's soccer record.
"They're going to be a strong team — anyone from here on in is going to be tough," Great Britain midfielder Rachel Yankey said on FIFA.com. "But we've shown we can live with anybody and the performance against Brazil especially shows that."
The Canadians are coming off arguably one of their strongest performances ever — a 2-2 draw with No. 4-ranked Sweden.
"This team just never gives up. It's another step on the road for us. It's what we wanted and we're on our way, but this is just one stop on the journey," said Melissa Tancredi, who has four goals in three games for Canada.
The game marks the 100th match in Olympic women's football history.
Elsewhere, Dave Calder and Scott Frandsen, silver medallists from the 2008 Games, hope to keep Canada's rowing medal streak going when they compete in the men's pair. They're in tough against heavy favourites Hamish Bond and Eric Murray of New Zealand.
Swimmer Ryan Cochrane begins his quest for another medal in the 1,500 metres after winning bronze in the event four years ago in Beijing, while Sinead Russell of Burlington, Ont., swims in the women's 200 backstroke final.
Canada's women's basketball team, fourth-place in Group B, faces Brazil.
Note to readers: This is a corrected story. An earlier version reported that Zelinka finished fourth in Beijing.
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