NEW YORK -- They lay on their stomachs, modified M-16 rifles aimed at targets, ready to fire away. And then a posse of Marine drill sergeants swarmed the six junior tennis players, bending over them and hollering in their ears in a frightening cacophony, doing everything they could to disrupt the teenagers' shots.
"The only way I can describe the feeling is like seven lions crouching around one sheep," 16-year-old Jarmere Jenkins of College Park, Ga., said in a videotaped postmortem interview with his coaches.
After that, how tough can it be to face a break point?
Jenkins was one of the players selected by the U.S. Tennis Association to spend five days in an abbreviated form of Marine training at Camp Pendleton outside San Diego. The full-immersion program was deemed so effective that the USTA is considering repeating it this fall and again next year, sending some players back for a second round, and perhaps, down the line, even instituting a version for girls.
USTA developmental coach Martin Van Daalen, who did two years of mandatory military service in his native Netherlands, got the project going. "I always thought it would be a neat thing to add this to the training, because what you do in boot camp is learn to control emotions under stress," he said.
The broader subtext was the growing perception that the U.S. junior ranks were getting soft, infiltrated by undisciplined, self-important, racket-throwing prima donnas whose attitudes were impeding their athletic progress.
"When you're a 14- or 15- or 16-year-old top junior player, a lot is given to you," said USTA managing director of player development Paul Roetert. "We were concerned about complacency."
Van Daalen routinely brings a group of juniors to Davis Cup competitions in the United States. Last year in San Diego, he had a chance encounter with Sgt. Major Keith Williams, a 30-year veteran of the Marine Corps, who had volunteered his unit to provide the color guard.
The two hit it off and began discussions with the Marine command about opening Camp Pendleton to the tennis civilians, "which was unheard of," Williams said. The first group traveled to the base for five days last February and included Jenkins; Chase Buchanan, 16, of New Albany, Ohio; Waylon Chin, 17, of Boynton Beach, Fla.; Jeff Dadamo, 18, of Tampa; Adam El Mihdawy, 17, of Long Island City, N.Y.; and Rhyne Williams, 16, of Knoxville, Tenn.
They packed light -- no cell phones, iPods or laptops allowed. No tennis rackets either. The teenagers arrived thinking they were in for an adventure. They soon found out how extreme that adventure would be.
After Williams made a brief introduction, two drill sergeants took over, leaned close to the boys' ears and began bombarding them with high-decibel orders in the empty, echoing barracks. "Don't breathe until I tell you to breathe!" one of the sergeants yelled early on.
Jeff Dadamo had envisioned boot camp as something like what he'd seen in the movies.
"Multiply it by 20," Dadamo, who played in the junior U.S. Open this week, told ESPN.com. "You can't describe it and the camera doesn't capture it. You could tell that they were doing everything they could to break us down as far as possible.
"The first two hours were probably the toughest part of the week. Some of the guys were shaking."
The campers lost all control of their lives from that point on. The drill sergeants instructed them on how to make their beds (crisp hospital corners), brush their teeth (start on the left side, don't leave the water running), march (upright posture, knees raised high), how to refer to themselves (as "Warrior Jenkins" or "Warrior Dadamo") and communicate (request permission to speak). For the first couple of days, the juniors weren't even allowed to talk to each other.
They were awakened the first morning at 5:30 by a sergeant banging on a trash can -- not that they'd slept much. Each junior had to patrol the barracks for over an hour in the middle of the night on "fire watch."
"It was all about taking them out of their comfort zone," said Williams, 49, who has retired from the Marine Corps and is now a motivational coach working as a USTA consultant. He conducted a similar boot camp program for the University of Southern California men's tennis program.
Jenkins said he and his buddies never got comfortable. "Every chance you had to think, going home was your first thought," he said during an interview in New York.
The juniors were occupied constantly from dawn until 9:30 p.m. After the shock treatment of the first day, they settled into a routine of physical activity and classes in marksmanship (using virtual ammunition in the form of lasers) and martial arts. Even meals, often an adolescent preoccupation, became an afterthought.
"I couldn't taste it," Dadamo said. "I was just eating food because I was starving. I was there to get food in my body so I could go the next day."
The players ran sand dunes, hiked the mountains above San Diego with heavy backpacks, learned to assemble and disassemble an M-16, observed actual Marine training, visited amputees and wounded Marines, and spent time standing perfectly still, envisioning a match point by point.
A video shot by Van Daalen and fellow USTA coach David DiLucia shows the juniors' expressions gradually changing from fear to stern concentration over the course of five days. But the players weren't the only ones undergoing a transformation.
"I can talk to them differently," said Van Daalen, who sometimes harks back to a specific boot camp experience when he is working with a player now. "If I'm more abrupt, they can take it. If I'm more direct, they know I'm doing it to make them better, whereas before they were so easily hurt."
Williams presented each player with a set of dog tags at "graduation" and informed them that if any one of them didn't live up to the new standards they'd absorbed -- spelled out in contracts -- he would come and take all their tags away.
He made good on that threat shortly afterward when the players reverted to more lax behavior at a tournament in South America, but has since returned the tags to a couple of players. Williams also has followed up with one player by spending time at his home working with him one-on-one.
"By the time they're 16, they've had thousands of repetitions of bad habits," Williams said. "It's like a wall with layers of paint. Some walls, you have to strip and start all over again and some just need one coat."
Jim Thompson, executive director of the Palo Alto, Calif.-based Positive Coaching Alliance, said he hopes the harshness of some aspects of boot camp-style training is balanced by support and reinforcement for what young athletes are doing right.
He added that youth coaches should not try to adopt the style of Marine drill sergeants. "There's already too much screaming in youth sports,'' said Thompson, whose non-profit advocacy group is devoted to collecting research and consulting. "It's driven kids out of sports."
Jenkins said he benefited psychologically from the experience, although he's not always as prone to making his bed precisely or saying "Yes, sir," quite as often. "When I get into a third set, I remember getting woken up at 5:30," he said. "My work ethic shot up. My results haven't done that yet, but I'm looking for a breakthrough."
After Dadamo won the marksmanship contest, Williams thumped him on the chest and called him "a warrior and a killer," in the figurative sense, of course. Dadamo was beaten in the third round of the junior nationals at Kalamazoo, Mich., last month, but fought his way through the losers' draw and finished fifth overall.
His mother, Jan, said she would send him again "in a heartbeat," even after seeing an hour-and-a-half DVD of the experience that left nothing to the imagination.
"I was not entirely a different person, but I had new values, kind of," Dadamo said of the boot camp's lasting effects. "I was a lot more disciplined on and off the court. I personally hope I'm lucky enough to do it again."
Bonnie D. Ford is a frequent contributor who is covering the U.S. Open for ESPN.com.