CAMP FOSTER, Okinawa — Kristen Arnold jumped, grabbed the bar and pulled herself up to balance on her hands like a gymnast.

The intense effort earned her one repetition. The muscular 29-year-old Department of Defense teacher needed several more to meet her CrossFit training goals for the evening.

But when Arnold dropped to the gym floor, blood was running down her palm, mixing with the white grip powder. The “muscle-up” had peeled back the skin on the inside of her thumb.

For many people, that would have been it for the night. Arnold just taped the injury and continued her grueling workout of Olympic lifts, 400-meter runs and handstand pushups at a gym near Kadena Air Base on Okinawa.

There was little time to nurse the wound — next week she might have to do the muscle-ups while competing against the world’s top CrossFit athletes. After winning regional competition in Asia earlier this year, her team of seven from the military community on Okinawa earned a spot in the global 2013 CrossFit Games in Carson, Calif., which will run Monday through July 28.

Arnold and her team are the face of competitive CrossFit in the U.S. military, a flourishing new sport that is a more extreme — and possibly more injury-prone — form of the high-intensity fitness craze that swept through the services nearly a decade ago.

The fast-paced and constantly varied strength workouts draw on Olympic lifting and gymnastics and often revolve around variations on squats, deadlifts and pull-ups. It is nothing new to the military — one of its most popular routines is named after a fallen Medal of Honor recipient, Navy Lt. Michael Murphy.

But a surge in global competition and media coverage has persuaded an increasing number of servicemembers to take gym training beyond fitness and test the far limits of their physical abilities as CrossFit athletes.

“This is probably the most competition this region has ever had,” said Jamie Light, the Okinawa team’s trainer and owner of the Reebok CrossFit Asia gym, which opened near the air base in 2008.

Finalists in the annual global competition of individuals and teams are drawn from Asia as well as sections of the United States, Europe, Africa and Australia.

Light said team competition in the Asia region — home to a large number of military bases and personnel — jumped from about eight teams last year to nearly 30 in 2013.

Overall competition in the games has also exploded. After starting with 123 athletes on a ranch in California in 2007, the games have grown to 138,000 participants in the open competition at the beginning of the season this year, according to CrossFit spokesman.

“It has gotten big, and the talent has gone up exponentially,” Light said.

His team is a cross-section of the military community on Okinawa and proof of the sport’s widespread appeal within the services. It consists of three airmen, a Marine, a teacher, a military spouse and an Japanese national from Okinawa.

To be competitive, team members work out intensely for two hours or more five days a week. On Thursdays, they take it easy with moderate exercise such as bicycling, jogging or playing sports. Sunday is their only full day of rest.

The routines are essentially the same as typical CrossFit workouts, but the competitors are pressed to achieve more exercise volume and heavier loads, often until their bodies and minds are exhausted and begin to fail.

Light said there is a clear line between coaching CrossFit for fitness and coaching for competition.

“If you are doing it for fitness, you are just trying to get better health and wellness,” he said. “I’m much more comfortable pushing [competitors] to their limits.”

CrossFit competitors are similar to athletes in other sports and are typically performing at 80 percent of their abilities due to aches and pains caused by the training workload, he said.

Christen Wagner, a 26-year-old Marine staff sergeant, is among the most experienced on the Okinawa team. Last year, she competed in the games as an individual, a daunting challenge that requires athletes to be versatile and skilled in any physical challenge.

This year, Wagner is nursing a recurring upper back injury that flared up as the team started training with heavier weight to prepare for the games. The injury led her to join the team, which allows members who are stronger in certain events to help carry the group.

“To do it individually is just so hard on your body,” she said.

Despite the pain, Wagner said there is “nothing better for finding your limit” — a line between being comfortable and passing out.

Those who compete and press hard against that line are often faced with deciding whether their mind is tricking them into quitting a physical challenge or if their bodies are really in too much pain to continue, she said.

From its start, CrossFit faced questions over safety.

Heavy Olympic-style lifts, for example, require a high level of strength and proper technique. A failed lift can result in catastrophic injuries even in Olympic athletes.

But as the popularity of CrossFit has ballooned, safety concerns have largely fallen to the wayside in the military. The training is now a common feature in base gyms around the world.

The Army issued an updated physical training manual last fall that includes exercises and approaches mirroring the intensity and excitement that has made CrossFit such a hit among the ranks, said Army Col. Francis O’Connor, a doctor and the director of Consortium for Health and Military Performance at the Uniformed Services University.

The service published a study of CrossFit in 2010 saying the training was replacing or augmenting traditional Army workouts. It found that a group of soldiers showed marked improvements in fitness after CrossFit training for six weeks.

“You can see the services are saying, ‘What the hell is this phenomenon?’ ... and they are trying to get their PT back,” said O’Connor, who is also a certified CrossFit instructor.

O’Connor said he is uncertain whether the recent boom in CrossFit — including the more intense form practiced for competition — is causing a higher level of injuries compared with other physical training and sports.

His CHAMP department, part of the university that trains medical professionals in the military, proposed a study of CrossFit, but the funding never materialized, he said. The Army study did not address injuries.

With the lack of research, training under a skilled or certified instructor and getting a health assessment by a doctor should be necessities for anyone competing in CrossFit, O’Connor said.

“You can’t just hop into a CrossFit training program,” he said.

Wagner said she was immediately attracted to the thrill of competition when she started CrossFit, but she still trained for more than a year before seriously considered joining one.

Wagner shrugged off any higher probability of injury through competition. “It’s just like any other sport — it’s risk and reward,” she said.

Her back injury will be an “annoyance” going into the finals Monday. For a Marine, it is something to shake off, just like the weariness from her permanent change of station back to the U.S. this month.

Those annoyances are just distractions overshadowed by what has drawn so many other servicemembers to the sport — the chance to prove herself among the best in the world.

“I think it comes with the territory” when serving in the military, she said. “There are a lot of A-type personalities who get into something and want to be the best at it.”

The games will be broadcast on ESPN3 in the United States. Viewers from outside the U.S. can follow the action at

Sign Up for Daily Headlines

Sign up to receive a daily email of today's top military news stories from Stars and Stripes and top news outlets from around the world.

Sign Up Now