ABC News' Producer Angel Canales and Editor Arthur Niemynski report:

Woodland Hills, CA., - U.S. Army veteran Juan Carlos Hernandez, 26, always liked sports but never imagined he would become a hard core cyclist six months after losing half of his right leg in Afghanistan.

While conducting a nighttime aerial mission, the helicopter that Hernandez was in was hit with a rocket-propelled grenade, and shrapnel penetrated his right leg.

"I tried getting up and I couldn't feel anything below my waist. I was like, 'Okay, it could be anything. My legs are numb, I can't feel anything.' I tried not to panic," Hernandez said.

The injuries were so severe that it required a below-the-knee amputation. It wasn't until he woke up at Bagram Air Force Base that he realized what happened.

"I looked down and I only saw one foot and I saw the other one all bandaged up and that's when it hit me," he said.

Hernandez joined the Army in 2006 and he was deployed to Afghanistan in 2008 after volunteering to be part of a task force with the 17th Cavalry.

"They were looking for guys who wanted to come on and be gunners," said Hernandez, who was a Chinook gunner crewman before he retired.

Hernandez said his recovery was painful.

"My first time walking without crutches it was painful but something I got used to," said Hernandez, who now lives in Woodland Hills, Calif.

He "took it slow and did everything my doctors asked," he said. "Slowly, I started doing more activities, jogging and then I started riding a bike."

During his rehabilitation at the Center for the Intrepid - Brooke Army Medical Center in San Antonio, Texas, a therapist noticed he became interested in cycling.

"She mentioned 'Ride 2 Recovery' and she recommended I get involved with the program," he recalled.

They provided him with a bike but using his prosthetic leg proved difficult. "Keeping the prosthetic leg on the pedal was the hardest because I didn't have any control from the knee below. I fell a couple of times but I was able to manage," Hernandez said.

Ride 2 Recovery is an organization that partners with the military and Veterans Affairs Voluntary Service Office to support mental and physical rehabilitation programs. Its main programs include Challenges, Honor Ride and Project HERO - all aimed to improve the health and wellness of wounded veterans through cycling as the core activity and to help them overcome obstacles they face. It also adapts bikes to suit the needs of cyclists with disabilities.

Hernandez joined Ride 2 Recovery in April 2010 and the group provided him with a bike. "It makes me feel alive and I enjoy the pleasure that comes with helping others," Hernandez said.

R2R events are rehabilitation rides rather than races and allow injured veterans to work towards their own goals. For Hernandez, his first Ride 2 Recovery ride was challenging.

"The Texas challenge was 360 miles long in 6 days. It was one of the hardest things I've ever done both mentally and physically. I feel like I completed something nobody thought you could do after losing a leg in combat," Hernandez said.

Part of the rehabilitation process for Hernandez was the peer mentoring he received - something that led him to become a Rider Assistant with Ride 2 Recovery. "We can all relate to our stories. Being able to be on the bike and share our stories with one another takes care of a lot of what we're going through and rehabilitation."

John Wordin, president and founder of Ride 2 Recovery, said: "Juan Carlos' commitment to cycling as rehabilitation is an inspiration to many."

"He leads by example, always ready to help fellow cyclists and bring them into the Ride 2 Recovery family," Wordin added. "Juan Carlos is a mentor to so many of the new riders providing them with a great role model and work ethic."

Hernandez said that being part of Ride 2 Recovery not only as a rider but staff member is one of Hernandez's biggest accomplishments.

"Being able to give back to other guys who have sacrifice so much, being able to go to the rides and meet everybody and some way help them in their rehabilitation and get back into the fight is the highlight for my life at this moment."

Second Tour is an ABC News digital series profiling the lives of military veterans who are doing unique things in the civilian world, including vets who took on an entrepreneurial venture to create a business, grassroots organization or a second career. For more stories visit http://abcnews.go.com/US/Second_Tour/.