The first part of rucking is the safety briefing. Best safety tip: Don’t call Green Beret Dan Plants “sir.” Second-best: Don’t call rucking “running.” And last but not least: “If you start going off into la-la-land, I need to know immediately.”

Such was the safety briefing at Suffolk Fire & Rescue’s Station 1 on Market Street on Friday prior to the GORUCK Challenge. But not to worry: The 24 participants were all firefighters, a set of folks more trained than the average citizen in personal safety.

Plants was leading the off-duty firefighters in the challenge, set for Sept. 11 to memorialize the lives lost in the terrorist attacks of 14 years ago, especially the 343 firefighters who died while trying to save others from the burning towers of the World Trade Center.

“We’re doing this as a way to honor those that lost their lives on 9/11,” said Travis Saunders, a firefighter who coordinated the effort. “I think it’s a way to memorialize the event and the guys that lost their lives in a physical and mental way.”

Rucking is an activity loosely defined as “carrying heavy stuff long distances.” The team on Friday was scheduled to spend up to 10 hours walking up to 20 miles from the Market Street station through the Great Dismal Swamp and back again.

Each team member had a 30-pound rucksack strapped to his back, and each had to help carry team weights that ranged from 25 to 120 pounds, including sandbags, water tanks, a log of solid wood and a steel plaque. The team also carried an American flag and a flag bearing the names of all the rescue workers who lost their lives on Sept. 11, 2001.

The team had 10 minutes following the safety briefing to choose a team leader and navigator and decide how to divide the carrying responsibilities for the team weights.

“It’s a team event,” Plants said. “There’s no individuals here.”

Besides the memorial and team-building aspects, the event served another purpose: To emphasize the importance of fitness in a physically demanding occupation that sees a high number of cardiac-related deaths.

Plants conducts the GORUCK challenges all over the United States but had good reason to think highly of this memorial challenge.

He was an Army mechanic when the planes hit the towers, and he soon found that, for him, it was “not good enough to just be a mechanic.” He wanted payback.

“My life from that point on changed,” he said, recounting his move to Special Forces. “I like to think I definitely brought a lot of payback to those a—s that did what they did on 9/11,” he told the group of firefighters.

He recalled how the firefighters in New York didn’t run from the towers that day. Instead, they ran toward, into and up them, carrying their own heavy oxygen tanks and protective gear and helping evacuate office workers.

“It’s only because of them that the casualty count was not higher,” Plants said. “When you start feeling sorry for yourselves, I want you to think about what happened 14 years ago.”