Aug 18 (Reuters) - To shouts of "Rip his head off!" and "Oh my God!" gladiators in medieval armor battle it out with steel swords and axes, one Saturday a month in New York"s Central Park. In one-on-one matches, members of Gladiators NYC wear helmets, chain mail and full armor weighing up to 100 pounds. They bash each other in the head with real weapons and violently kick, punch and throw each other in the dirt, using full-contact mixed martial arts techniques in three one-minute rounds. In melee matches, up to four knights fight to the finish, until one is left standing. Gladiators NYC is the flagship program for free martial arts and fitness nonprofit Santa"s Knights, founded by 40-year-old Damion DiGrazia eight years ago. DiGrazia"s path to teaching martial arts to children and aspiring knights is an unusual one, from the U.S. Air Force to Columbia University to a master"s in finance at Harvard University, and then as a management consultant at Morgan Stanley (MS.N). "It was really like I had arrived," he says, standing outside of his former work place on a sweltering August day. But as he sat there in his big glass tower, he realized that his interest in money - the driving motivator behind working at one of the top three investment banks in the world - was missing. "If money doesn"t motivate you, then what do I do? I was like, "What motivates you? Helping people, I like to help people." My natural inclination for life, for myself, is a life of altruism and anything that diverts me from that path, hurts my soul," he says. For DiGrazia, his way of helping people was to start a nonprofit that offers free martial arts and fitness classes to all those who seek them. "We just hit the core of it, which is, be healthy, do fitness," he says. "And when you start to do more fitness, you eat more healthy. You change your lifestyle. And now we"re saving lives." Reporting by Roselle Chen and Eduardo Munoz; Editing by Steve Orlofsky Our Standards: The Thomson Reuters Trust Principles.