Jason Sturm says he cannot remember what it was like to have two legs.

For 14 years now, Sturm has used an artificial limb, called a prosthesis, where the lower part of his left leg once was. The metal leg attaches about eight centimeters below his knee.

"It was just 14 years ago. And the reason why is because I know that that is the old me, that is not the new me. The new me is what is here now."

The "new" Sturm is athletic, fit and strong. He has a beard, short hair, and a tattoo on his right arm that reads "Reject your sense of injury and the injury itself disappears."

Sturm's injury happened in March of 2002. He was 22 years old. He had joined the U.S. Army after high school, and was taking part in a military training exercise at Fort Drum in New York.

An artillery round missed its target. Instead, it exploded less than two meters behind Sturm.

The explosion killed two soldiers. Sturm survived, but his left leg was severely injured.

For eight months, Army doctors tried to save Sturm's leg. They performed surgeries and other treatments. But nothing made it work again.

So Sturm chose to have a medical operation to remove his leg.

"I had already disassociated with my leg. I had already seen it as its a dead limb, it's doing nothing but holding me back."

Two months after the surgery, Sturm tried on his first prosthesis. Physical therapy treatments helped him return to basic everyday activities.

After the accident, Sturm gained more than 20 kilograms. He was out of shape and overweight, like he was when he was a kid.

He decided to change.

Sturm slowly returned to doing sports and activities that he had always enjoyed, like weightlifting and running.

He even started learning new sports. In 2011, a friend sent Sturm a list of workouts. His friend said to him, "Hey, you should try this stuff. It's called CrossFit."

"And I looked at all the things that these people were doing and I was like, there's no way I can do that as an amputee..."

But as he often does, Sturm decided to push himself. Within one day, he says, he was "hooked."

Still, it took months – even years – for Sturm to learn how to do some of the difficult exercises with his prosthesis.

CrossFit is an intense exercise program. It combines movements from several different sports and activities. It is meant to strengthen a person's core and work on conditioning.

Just one year after he first tried CrossFit, Sturm became a CrossFit coach. He started training people known as "adaptive athletes," like himself.

"What an adaptive athlete is it's someone that requires a permanent adaptation to do specific movements. So I require a prosthesis to do the movements that I do in CrossFit. So therefore I am an adaptive athlete..."

He says one of the most important parts of coaching amputee athletes is helping them trust their prosthetic device.

"There's just a level of mistrust and discomfort."

Sturm also tries to give his athletes the "tips and tricks and tools" that they need to get stronger.

It did not take long for Sturm to notice that CrossFit felt similar to the Army. CrossFit is a group workout. People in the classes motivate each other to finish the exercises, just as soldiers push each other in the Army.

Sturm says he hopes more injured Army veterans give CrossFit a try.

"What we're trying to do is we're trying to get vets to have an understanding that, that same social comradery, that same feeling you got when you worked out with your entire unit in the military, can be re-enacted by coming into a CrossFit gym and work."

At first, Sturm coached CrossFit while also working a full-time job. Then, in 2013, he decided to go back to school to study Kinesiology and Exercise Physiology. Kinesiology is the study of how the body moves.

And in 2014, Sturm decided to quit his job and spend more of his time coaching CrossFit athletes.

Sturm calls working with adaptive athletes one of the most rewarding parts of his what he does.

"Every amputee is different, even if you find someone that is set up exactly like me and looks like me. Their adaptation and their needs are different. So working with adaptive athletes is something that literally is a driving force to make me a better coach."

Today, Sturm lives in northern Virginia. He is vice chairman of Crossroads Adaptive Athletic Alliance. The non-profit group helps bring together amputee athletes and their coaches.

Last year, Sturm and his wife, Rachel, opened their own CrossFit gym in Ashburn, Virginia. It is called Old Glory Gym. The sign on the gym was inspired by Sturm's Army unit's official sign. He replaced two swords with two bench press bars in the design.

CrossFit is not the only sport Sturm has learned since his accident. He also learned how to bobsled. The winter sport involves guiding a big, fast sled down a steep, curvy, icy path.

Just as he did with CrossFit, Sturm took to bobsledding quickly.

"One day, a gentleman out of Park City, Utah, just sent me a message and said, ‘hey, would you like to try out as a brake man for the U.S. para-bobsled team?'"

A "brake man" pushes the sled at the beginning of a race and then stops it – with brakes -- after it crosses the finish line. Brake men do not steer or drive the sled.

Just months after trying out for the U.S. team, Sturm traveled to Europe in early 2015 for his first-ever bobsled races. He was surprised to learn that the competitions would only involve one-person teams. That meant Sturm would have to drive the sled himself.

In two races, Sturm placed second and then first. Those results made him the para-bobsled World Champion.

Sturm hopes to grow the sport among adaptive athletes.

"So my goal is, get us noticed, compete when I can, and recruit as many people into the sport as I can."

Sturm's goal for bobsledding is similar to his goal with nearly everything he does in his life.

"Being able to do this work, being able to get up in the morning and effect a positive change in people's lives is hands down what I live for and why I do this. What drives me and what is the most impactful part of my life and is my life is helping people."

I'm Marsha James.

Marsha James wrote this story for Learning English. Ashley Thompson was the editor.

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artificial limb - n. a replacement for a missing leg or arm

prosthesis – n. an artificial device that replaces a missing or injured part of the body

artillery round – n. ammunition consisting of metal casing containing an explosive charge fired from a large gun

disassociated – v. to end your relationship with or connection to someone or something

hooked – adj. very interested in and enthusiastic about something

core - adj. relating to the muscles of the torso

comradery – n. a feeling of good friendship among the people in a group

rewarding – adj. giving you a good feeling that you have done something valuable, important, etc.

curvy – adj. having a continuous bending line

took to – phrasal verb. to begin to be interested in something

para – sports played by persons with a disability or adaptive athletes