Rucking, a fitness activity that's growing in popularity, is much simpler than it might sound.

Inspired by a military training exercise, it involves walking while carrying a heavy load — usually in a backpack — to reap a number of health benefits.

As the weather cools down, adding weight to your fall walk or hike can enhance your workout, fitness experts say.

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Retired Army Green Beret Jason McCarthy started his Florida-based company, GORUCK, based on the technique he learned in the service.

The company has conducted more than 10,000 live rucking events since 2010, according to its website, and there are more than 500 independently owned GORUCK clubs around the world.

In an on-camera interview with Fox News Digital, the CEO called rucking "really simple," as it only requires putting weight in a backpack or "rucksack" and walking.

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"It's carrying weight," he said. "Rucking is the foundation of special forces training — or any infantry training, for that matter."

"You pick up weight, things are heavy – ammunition and weapons and mortars and food and batteries and radios … and you have to transport that, so you're rucking it."

The concept of rucking goes all the way back to the hunter-gatherer days, McCarthy noted.

"The original rucksack was whatever animal you brought back to the tribe to eat for dinner and someone had to put that on their back and carry it," he said.

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"Humans are uniquely built to carry like that, so this is not some fad, it's not some exercise machine. It's something we're innately built to do."

Rucking can be considered "cardio for people who hate cardio," McCarthy said, as it allows people to increase their heart rate without exerting too much energy.

The activity is also much lower-impact than other exercises like running, and it can be scaled back depending on how much weight is added, he noted.

"It’s really accessible to all," McCarthy said. "Go out and be more active."

McCarthy recommends that first-time ruckers "add a little weight, add a little challenge to your life — 10, 20, 30 pounds — and just sort of carry it around."

An additional challenge is to ruck while walking the dog or pushing the kids in a stroller, he said, with some added weight in a backpack.

In a separate conversation with Fox News Digital, celebrity personal trainer Kollins Ezekh confirmed that rucking can enhance cardiovascular endurance, strengthen muscles and improve posture.

Rucking engages the core, back, legs and shoulders, providing a "full-body workout" without high impact on the joints, according to the Los Angeles-based trainer.

"Rucking is also a calorie burner, making it a great option for those looking to shed weight," he said. "It’s simple, requires minimal equipment and can be scaled up by adjusting the weight."

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Ezekh has recommended rucking to his personal training clients, especially those seeking a low-impact cardio option.

"Clients who have incorporated it into their routines have reported increased endurance, [as well as] improved posture and strength, particularly in their core and back," he told Fox News Digital.

"It also adds variety to their workouts and complements other forms of exercise like running or strength training."

Although it can be an effective workout, Ezekh cautioned that improper rucking technique can come with risks.

"Carrying too much weight or not distributing it evenly can lead to poor posture, strain on the lower back or joint issues," he said, noting that it's best to start with a lighter load and slowly increase the weight.

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"The key is to progress gradually and stay mindful of form, ensuring long-term sustainability without injury," he advised.

Proper footwear and technique are also key to minimizing risks, Ezekh said, ensuring that the weight is balanced and preventing unnecessary strain.

The activity can be modified to meet almost any fitness level, the trainer noted – yet older adults should consult with a health care provider before trying it.