The Boston Marathon bombing has engendered an outpouring of grief and sympathy from around the world — but few voices have been louder than those from the running community. And in the wake of the gruesome attack, many runners are still looking for a way to channel their anger and grief into something more productive. Here, three ways that runners can express their sympathy and support the victims of the Boston Marathon bombing:

1. Run 26.2 miles
Runner John Mulholland has taken to Facebook with a grassroots movement called "Run 26.2 for Boston." Essentially, he's encouraging runners to go on their own personal marathon-length runs "for the ones for whom today's 26.2 might have been their last, and for the ones that didn't finish." More than 3,000 runners have already committed to run the distance at their own pace, with more signing up to join all the time; interested runners can visit the official event page.

2. Wear a race shirt
Popular running website Run Chat has asked its readers to "show the world how strong the running community is" by wearing race shirts whenever possible this week. "When you head out for a run, wear a race shirt. If you can dress casually to work or have the day off, wear a race shirt," suggests the website. Anyone unable to wear a race shirt is encouraged to wear blue and yellow, the officials colors of the Boston Marathon.

3. Host a blood drive
A widely circulated tweet by NBC Sports revealed that some marathon runners "crossed [the] finish line and continued to run to Mass General Hospital to give blood to victims." Though the American Red Cross has since tweeted that they currently have enough blood on the shelves due to the "generosity of volunteer blood donors," some running groups are already planning to collectively donate blood in honor of the victims in the weeks and months to come. Interested runners can register to host a blood drive on the Red Cross website.