Bothered by an arm injury, the Kamloops, B.C., native failed to make the final in the event Friday despite being among the favourites. Armstrong's throw of 19.84 metres left him 20 centimetres short of the eighth and final spot in the medal round.
"My arm has been sore, it flared up before I left for Turkey but it got better and I was hoping there wasn't going to be any issues," Armstrong said. "Unfortunately it flared up on me again and just didn't feel right when I was extending to throw so I was hesitant in the circle to push hard and risk any serious injury."
Canada's Justyn Warner and Michael LeBlanc, in the 60 metres, and Nikkita Holder, in the 60-metre hurdles, all advanced to Saturday's semifinals.
Nataliya Dobrynska of Ukraine set a world record in the pentathlon, showing she is ready for a repeat Olympic gold medal at the London Games.
Armstrong, meanwhile, faulted on his second and third of three throws, to finish ninth.
The 31-year-old said the injury isn't a "long-term concern."
"The athletic therapist is working on it and this will all be behind me very shortly," Armstrong said. "I'm still in a heavy training phase so that does take a toll on the body."
Armstrong was ranked No. 1 in the world last year and will be among Canada's medal hopefuls at the London Olympics.
Armstrong's rival David Storl, who beat the Canadian at the world outdoor championships last summer, had the best qualifying throw of 21.43 metres.
Warner and LeBlanc both finished second in their heats of the 60 to move on. LeBlanc, from Riverview, N.B., ran 6.74 seconds.
"We've had a plan all season to be here, I'm not going down without a fight," LeBlanc said. "Today was a good test of where I am."
Warner, from Markham, Ont., ran 6.75.
"I came here with the objective of making the final, today was the first step towards that," Warner said.
Holder, a 24-year-old from Toronto, was third in her heat and posted the fifth-fastest hurdles time overall of 8.15 seconds.
"I'm happy to move onto the next round," Holder said. "This is my first world indoors and I wanted to make sure I didn't false start.
"I had a slow start but came on stronger over the last few hurdles, looking to build on that for next round."
Dobrynska, the 2008 Olympic heptathlon champion, upstaged favourites Jessica Ennis and Tatyana Chernova with a sterling long jump and a gutsy concluding 800 metres to become the first woman to break the 5,000-point mark in the five-event discipline.
"I was confident that I could do it here," Dobrynska said. "I was mentally ready for this record for a long time."
She beat the 20-year-old mark of Irina Belova with a score of 5,013 points. Dobrynska was only nine years old when the Russian set the old record of 4,991 points.
Defending champion Ennis, who led through the first three events, was left with silver and a British record 4,965 points, and Austra Skujyte set a Lithuanian record of 4,802 for bronze. Outdoor heptathlon world champion Chernova finished fifth.
"It is the worst feeling you could ever have, seeing your name in first place and then in second," Ennis said. "I need to make sure I learn from these experiences, get it right and turn silver into gold this summer," said Ennis, who is one of the host nations most bankable Olympic stars.
It was only the second gold for Dobrynska after she also upset the favourites at the 2008 Beijing Olympics. She had been waiting to get the record for a long time.
"There was always a little something going wrong that prevented me from breaking it," she said.
But not Friday at the world championships, when her feat earned her a payday of US$90,000.
Dobrynska had to share the limelight with the starting gun and bad acoustics at the Atakoy Arena, a combination which eliminated some of the top sprinters from the three-day event.
Amid near-incessant complaining from athletes, unbeaten Lerone Clarke sat in the blocks for almost half a second after the gun. He didn't advance from the first round of the 60 metres.
American runner Kristi Castlin failed to finish her 60 hurdles race since she thought everyone would be pulled back for a false start. It didn't happen and it turned Sally Pearson into even a bigger favourite.
The Australian lived up to her billing when she set a continental record of 7.85 seconds in the heats and saw one of her toughest rivals go out.
In a packed program, Ethiopian great Meseret Defar set off on her quest to become the first female athlete to win five world indoor gold medals in a row, easily winning her 3,000 heat.
If the Ennis-Chernova duel turned into a one-woman show for Dobrynska, the 3,000 face-off between British runner Mo Farah and American rival Bernard Lagat also failed to deliver.
Instead of reigning regally over the heat they shared, they had to scramble up to the line to secure their places in the final as five went for the line with four places available. Within a jumble of .30 seconds, Farah was second and Lagat was third.
With files from The Associated Press.Suggest a correction