Thousands of CrossFit athletes and workout enthusiasts are hitting the gym next week for one common purpose: to honor America's fallen service members.

On April 29, CrossFit locations and other gyms throughout the country are taking part in the annual "Manion WOD" (Workout of the Day) event organized by the Travis Manion Foundation (TMF).

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People participating in Travis Manion Foundation's annual Manion WOD to honor the nation's fallen heroes.  (Travis Manion Foundation)

Ryan Manion, president of the Travis Manion Foundation, told Fox News Digital that CrossFit gyms will sometimes put out a "workout of the day," or WOD, to honor fallen heroes who were active in the CrossFit community.  

For the past eight years, numerous gyms have dedicated a workout to Manion's brother, 1st Lt. Travis Manion, who was killed by an enemy sniper in Iraq in April 2007 when he was pulling his wounded teammates to safety. Manion was 26 years old.

People participating in Travis Manion Foundation's annual Manion WOD to honor the nation's fallen heroes.  (Travis Manion Foundation)

Ryan Manion described the "Manion WOD" as an "extreme" leg workout that was tailored to her brother, known for having a stronger lower body. 

The workout consists of seven rounds of a 400-meter run and 29 weighted back squats, 135 pounds for men and 95 pounds for women. 

"Your legs are dead after you do it," Ryan Manion said. 

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Even in the midst of the grueling workout, Ryan Manion says she tries to remind herself that "as hard as this is, it's not as hard as what our men and women who are on the front lines are doing for us every day." 

People participating in Travis Manion Foundation's annual Manion WOD to honor the nation's fallen heroes.  (Travis Manion Foundation)

Though the event is named the "Manion WOD," the goal is to "galvanize communities" around honoring "all of our fallen service members who have given their lives," according to Manion. 

The event is probably the most challenging one the organization has, but It's designed to push people in "even deeper ways," she added. 

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"A lot of times we don't always understand what we're capable of achieving," Ryan Manion said. "There's no better way to gain inspiration from the men and women who have given their lives in service to this country."  

People participating in Travis Manion Foundation's annual Manion WOD to honor the nation's fallen heroes.  (Travis Manion Foundation)

More than 156 gyms and 2,000 people have already signed up to partake in this year's Manion WOD. 

If you don't belong to a gym, Ryan Manion said participants can still sign up and take part in the virtual events. 

The event's registration fee benefits the nonprofit, which works toward helping veterans and Gold Star families transition to civilian life, continue serving out of uniform and become character role models for their communities.