Last week, Army Sgt. Sandra Coast graduated from Basic Combat Training at Fort Leonard Wood in Missouri, notching some of the highest physical fitness scores in her company. What makes this particularly remarkable: At age 51, Coast is 222 percent older than the average newly minted Army grunt. Nicknamed "Grambo," Coast enlisted because she has a special place in her heart for troops — her son is Marine Corps Pfc. Jeff Coast — and a strong desire to serve. Still, "everybody in the world thinks I am a total nutcase," she tells the Armed Forces Press Service. A look at Coast's inspirational story:

Does the Army usually take 51-year-old women?
No. The Army let Coast join the Reserves because she served in the Navy from 1982 to 1993. She tried to enlist at the same time her son joined the Marines, but "before the recruiters would even talk to me, I had to lose 30 pounds," Coast says. "I went from sitting at home every night eating ice cream to exercising and watching what I ate." A paralegal specialist, Coast hoped to work with active-duty troops, but "they are not taking people as old as me for active duty," she says. Instead, she was assigned to an Army Reserve "virtual unit." That means "everything I do will be by the Internet and phone," Coast explains.

But she still had to complete boot camp?
Much to her surprise, yes. "I wasn't quite expecting to be running around with an M16 and all of this gear," Coast said. "We carried M16s during Navy boot camp, but we never shot them. Here we are shooting several times a week," with heavy gear on. "Everything about basic training is pretty tough," she says, "but living with more than 30 teenage females is one of the hardest things."

How did other grunts react to "Grambo"?
"We don't treat her any different, and we don't see the privates treat her any different," says Coast's first sergeant. Well, some of the men are particularly nice, Coast qualifies. "They will do little things that they probably aren't supposed to do, like give me their seat on the bus and hold the doors for me." Other situations are tougher. During hand-to-hand combat training, "we had to slap each other in the face," Coast recalls. "The poor guy that was up against me said, 'I cannot do this. I cannot slap her.' I told him I would pay for his counseling when we were done. I was slapping him — he finally slapped me."

What does her son think?
"She is hardcore," he says. "She is doing what most people her age would consider crazy," and "I hope when I get older, I am still active and do all kinds of cool stuff."

Sources: American Forces Press Service, The Stir, TIME, Washington Examiner