VANCOUVER -- Registration for this weekend's Vancouver Sun Run, Canada's largest 10-kilometre road race that draws tens of thousands of participants, has been bolstered by the Boston Marathon bombings as runners refuse to be deterred by the tragedy.

Sun Run chief organizer Jamie Pitblado said Tuesday that registration has increased in wake of the two bombings that killed three people and injured more than 140 others near the Boston Marathon finish line.

Pitblado said registration for the 10-kilometre event has already surpassed 45,000 runners, and the number is expected to continue to climb. In recent years, the event has averaged 49,000 participants, but Pitblado said he would "never underestimate the power of the human spirit to get out and show support for Boston."

The event's participation record was just over 59,000 in 2008. Pitblado does not expect the record to be challenged, but said organizers will have to consider opening up the event to more than 50,000 entrants if there is a rush on registration.

"We've been completely overwhelmed by what is happening in the response from runners," Pitblado said. "Our registration in the last day and a half has picked up.

"I think people are talking about it in the social media circles, that the best way to show their support for what happened in Boston is to get out and participate in the Sun Run. We're just humbled that the community has reacted to this in such a positive way."

Despite the increase, runners are still feeling anxious about participating in the Sun Run and other mass-participation events, said Running Room store founder John Stanton.

"I have a lot of conversations with runners in the last day and a half, and I can tell you candidly that there's a great deal of anxiety with some people," said Stanton. "What happened in Boston was horrific, and it happened in an area which is normally the elation of an event, the finish line.

"For a lot of runners, it's created some anxiety in people who train for the Sun Run or Vancouver Marathon."

Angela White, a former Boston marathoner competing in her first Sun Run this weekend, said the event will not be as special as it would have been if the Boston bombings had not occurred.

"It's kind of like a sacred thing that's been taken away now," said White, who has been running seriously since 2007.

White does not know if she is worried about a similar tragedy occurring at the Sun Run, but she is not heading to the event with the usual upbeat feeling that she gets from other events.

"I think the mood isn't going to be as happy or just kind of that nervous excitement you get with those kind of events," she said. "I think it's going to be a little bit more sombre."

Sun Run organizers met Tuesday with Vancouver police and fire department officials to discuss whether security needs to be beefed up in light of the Boston bombings.

Security is being increased for this week's London Marathon, which like Boston is one of the world's premier long-distance races. Conversely, organizers of the Hamburg Marathon in Germany said they did not plan any changes to their security measures their race on Sunday.

Stanton said he's confident that security will be increased at the Sun Run, but it will still be limited.

"It is a 10-kilometre course, and to protect that and say that (security) is tight is silly," said Stanton.

But, he added, it's important that people participate this year in order to remember the Boston victims -- and stand up to terrorism.

"It will be a celebration of our liberties and the values that we all have to hold so high," said Stanton.

Running Room stores play an active role in preparing runners for the Sun Run and other events.

Stanton said 80 per cent of the people he has spoken with have the attitude of "we're not going to let terrorism or evil take over the good things in our lives."

He said in addition to serving as athletic events and achievements, the Sun Run and other runs promote positive lifestyles and raise funds for worthy community causes.

"It's about our freedoms and we don't want people to lose that (sense of freedom)," he said.

The Running Room is organizing a tribute to the Boston Marathon bombing victims by holding a run and moment of silence Wednesday night at 118 locations to remember the people who were affected directly by the attack.

"We live in a free world, and our freedoms are important to us," said Stanton. "Going to runs like the Sun Run is no different than (getting) on planes after 911.

"We're still going to go to hockey games. We're still going to go to baseball games. We're still going to have Olympics. We're still going to have Commonwealth Games. We're still going to go to large concerts and other large gatherings with crowds, and we're going to do that because we're not let terrorists rule the lifestyle that we have in the free world.

"And, I think, there's a consensus among the running community. It's a tight community, and it's supportive, and it's encouraging, and it supports that whole community atmosphere. It's time we stood up and took those freedoms and stood guard on them."

Angela White, 43, who ran in the 2010 Boston Marathon and will travel from her home in Fort Nelson, B.C., to take part in her first Sun Run, welcomed Stanton's idea of runners increasing registration to show support for the victims of the bombings.

"I like that idea," she said. "It's such a community. You may not know everybody running, but at the time of the race you meet really amazing people and have these amazing conversations. You may never see them again, but it's like this extended family."

Before heading to work at her stakeholder relations job with Encana on Monday, White programmed her PVR to record the Boston Marathon, as she does every year. After seeing TV footage of the tragedy at lunch, she returned home later to watch the racing recording, which had stopped before the bombings.

She was left with a strange feeling as she watched runners and wondered whether they were among the victims.

"I've had a lot of conversations with runners today about it," said White, who wore her Boston Marathon shirt to work. "It's just such a sombre feeling. I don't know.

"It's just so shocking. I think everybody's just completely in shock."

Kelly Wiebe of Swift Current, Sask., who recently completed his fifth and final season competing for the University of Regina, will not return to defend his overall 2012 Sun Run title. A University of Regina spokesman said Wiebe is "banged up" and the decision has nothing to do with the Boston bombings.