She had just been through a excruciating 10-minute wait to see if her dazzling women's trampoline routine would hold up against two seasoned veterans from China. It wasn't until defending champion He Wenna stumbled at the end of her routine that MacLennan knew she had clinched Canada's first gold medal at these Games.
"It's exciting and honestly it's still a bit surreal," MacLennan said.
And the excitement continued. With Ryan Cochrane's silver in the men's 1,500-metre freestyle and a bronze on the cycling track in women's pursuit, it was clear Canada had its Olympic swagger back.
Canada remained solidly on track to finish top 12 in total medals in London. Through eight days Canada has 10 medals — one gold, three silver and six bronze — and sits 11th in the overall standings.
Saturday's medal hat trick came at a pivotal time as the Games reached its halfway point. Canada had performed well, but the coveted gold medal remained elusive heading into Day 8 in London. And the optimistic mood from a string of early successes was in danger of turning sour after a disappointing Day 7 saw three medal hopefuls come up short.
It looked like it might be another rough day when Edmonton's Paula Findlay placed last among finishers in women's triathlon. A heartbroken Findlay was in tears as she crossed the finish line, repeatedly saying "I'm sorry."
But as MacLennan's soaring routine earned her a personal-best score of 57.305, the country's Olympic future looked brighter.
"I was shocked. It's the biggest score that I've ever gotten," MacLennan said. "I knew it would be a tough one to catch. But you never want to get ahead of yourself. You want to wait until all the competitors are done."
Teammate Karen Cockburn turned to MacLennan and told her that her score was a winner.
MacLennan wasn't so sure.
"I didn't want to get too ahead of myself," the native of King City, Ont., said.
But Chinese favourites Huang Shanshan and He couldn't reach the impressive bar set by MacLennan, and Canada topped the podium for the first time in London. Huang and He won silver and bronze respectively.
Cockburn, from Stouffville, Ont., just missed adding to her trophy case with a fourth-place finish. She had won medals in the last three Olympics.
Instead it was MacLennan's time in the spotlight as she vastly improved on her seventh-place finish at the 2008 Beijing Games.
"Rosie was really strong, her score was huge," Cockburn said. "The other gymnasts could feel the heat after her score. I wasn't really surprised that she won. We pushed each other hard in training, I'm really happy for her."
Prime Minister Stephen Harper congratulated MacLennan in a statement.
"Through her hard work, dedication and sportsmanship, Rosie has proudly represented Canada on the world stage," he said.
Canada's best day so far in London continued when Cochrane took silver in the gruelling men's 1,500 freestyle, giving Canada at least two swimming medals for the first time since the 1996 Atlanta Games.
Cochrane, who won bronze in the event four years ago, held off defending Olympic champion Oussama Mellouli of Tunisia and finished in a personal-best time of 14 minutes 39.63 seconds.
"It was a tough fight the last 100 metres," Cochrane said. "I was going to fight, probably to the death, to make sure he didn't get his hand on the wall first."
Cochrane was certainly happy to win a medal, but he said he had his sights set higher.
"It's a double-edge sword because I wanted to be vying for that world record," he said. "I wanted to be five seconds faster. I think I did underestimate how hard the mental side of this meet would be."
China's Sun Yang beat his own world record to claim gold in 14:31.02.
On the cycling track, Tara Whitten of Edmonton, Gillian Carleton of Victoria and Jasmin Glaesser of Coquitlam, B.C., finished the team pursuit bronze-medal race in three minutes 17.915 seconds. Australia was timed in 3:18.096.
"We knew it was going to be a battle," Glaesser said. "We know they start off fast but we knew it was going to come down to the last lap. It was a challenge but we were 100 per cent committed to do our best."
Britain won gold in a world-record time of 3.14.051. The United States took silver.
In other Canadian results:
— Jessica Zelinka of London, Ont., finished seventh overall in women's heptathlon. Brianne Theisen of Humboldt, Sask., finished 11th.
— Cameron Levins of Campbell River, B.C., finished 11th in the men's 10,000 metres. Mohammed Ahmed of St. Catharines, Ont., finished 18th.
— Toronto natives Alex Bruce and Michelle Li fell 21-9, 21-10 to Russia to finish fourth in women's doubles badminton.
— Canada's men's table tennis team fell to Japan 3-0 in a first-round match.
— Zach Bell of North Vancouver, B.C., was ninth overall after the first day of the men's track cycling omnium.
— Justyn Warner of Markham, Ont., advanced to the men's 100 semifinals with a third-place finish in his heat. His personal-best time of 10.09 seconds matched world record holder Usain Bolt — although Bolt easily won his heat.
— Melanie Blouin of Quebec City finished tied for ninth place with a result of 4.25 metres in her women's pole vault group to miss out on Monday's final.
— Jennifer Abel of Laval, Que., and Emilie Heymans of St-Lambert, Que., both advanced to the women's three-metre springboard diving final. Abel was fourth in qualifying with 353.25 points while Heymans followed in eighth with 331.35.
— Eric Lamaze of Schomberg, Ont., had a clean run through the first qualifier to match 31 other riders at equestrian's individual jumping competition. Ian Millar of Perth, Ont., knocked down one gate for four points. Jill Henselwood of Oxford Mills, Ont., also knocked down a gate and had a time penalty point for five, while Tiffany Foster, also of Schomberg, knocked down two gates for eight points.
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