Lining up at least twice a week beside fellow students young enough to be his grandchildren, 63-year-old Ron Roe stretches, kicks and punches his way through classes in the Korean martial art of tae kwon do.

“Personally, I never thought I could achieve a black belt because I’m getting kind of old,” says Mr. Roe, a semiretired home-health-care worker in Aurora, Colo.

A growing number of older Americans are exploring martial arts such as tae kwon do and judo as a way to stay physically and mentally fit. With its kicks, punches and take downs, they are finding the sport brings a number of health benefits as well as increased confidence and respect.

Earning a black belt, the traditional symbol of self-defense proficiency, took Mr. Roe nine years after his first class at age 50. Since then he has advanced in rank to third-degree black belt, a rise accomplished by less than one of every thousand martial-arts students of any age, according to veteran instructors.

It’s a far cry from tai chi, the Chinese system of slow, graceful noncontact movements long associated with older adults. But so-called hard martial arts—tae kwon do, karate, kung fu, judo and aikido—are attracting more students age 50-plus. Mr. Roe, who credits his rough and tumble workouts with increasing his flexibility and balance, says, “Anyone my age can do it if they have the desire.”

Of course, the kicks of older combatants may not be Bruce Lee-style head shots, and they don’t have to be. Instructors at many of the roughly 30,000 commercial martial-arts schools in the U.S. increasingly are tailoring programs to older students, in whom they see the potential for an expanded clientele. AARP, the Washington-based advocacy group, says martial-arts are becoming more common at community recreation centers, YMCAs and wellness facilities.

Growing Ranks

Michael C. Weimar for The Wall Street JournalMark Copeland (right) spars with fellow student John Gibson during a class on defensive tactics at the Gary Hernandez Martial Arts school in Florida.

The ranks of older enthusiasts seeking black belts are bound to rise, says Vonda Wright, an orthopedic surgeon at the University of Pittsburgh’s Center for Sports Medicine who specializes in treating older athletes. “I see them increasingly reaching above and beyond the limits of what they have been told their bodies can do,” she says.

Steven Tsapos, a 71-year-old retired tavern owner in Warren, Ohio, says that after his tae kwon do classes four times a week, “I feel like a million bucks. For older people, I think it’s the best exercise there is.”

Like many programs, the commercial school he frequents makes some adjustments to his regimen, such as restricting the force of contact in sparring sessions. “We control the power” so that the feet and fists land essentially as light taps, says Louis Italiano, Mr. Tsapos’s instructor at the Austintown ATA Black Belt Academy in Youngstown, Ohio. Mr. Tsapos jokes that such limits are partly for the benefit of his younger opponents: “How would it look if I were to knock down a 17-year-old?”

Throwing down bigger and younger male practice opponents gives a certain satisfaction to Gail Chodera, 55, who trains twice weekly at Castle Rock aikido in suburban Denver. Her chosen discipline focuses on using precise pressure to lock and twist an adversary’s wrists and other joints. “I love the combining of the physical part and the mind to get the techniques just right. Sometimes I do, and the big guys go down. Sometimes they don’t.”

Although commercial schools increasingly offer classes separate from children, they sometimes classify high-schoolers as adults. Instructors say many older students seem energized by working out with younger ones. And sometimes the energy is contagious.

“Older students can be very inspirational,” says Bill Pottle, the owner of the school where Mr. Roe trains. “They often have an uncommon determination that can set a great example for younger people.”

Mark Copeland, a 54-year-old retired plumber in Zephyrhills, Fla., trains in a modified form of tae kwon do called “realistic defense tactics” at the Gary Hernandez Martial Arts school, also in Zephyrhills.

A few months after having both hips replaced in 2008, Mr. Copeland says, he discovered martial arts while looking for a new exercise routine. “I had to use a cane to walk into the place,” he recalls.

Now after two years and a green belt—about halfway to black—Mr. Copeland says, “I get around a lot better, have improved my balance and don’t need the cane.”

Culture vs. Technique

Yet the culture of a martial-arts program is at least as important as any techniques taught, says Mr. Hernandez, an instructor for two decades. “If you’re shopping for a class, look for a sense of humor in the teacher and the students,” he says. “I’m 45, I like pasta and I have a tummy. I’m not running a boot camp.”

The hand of Mr. Hernandez identifies a “strike point” at Mr. Copeland’s temple, where the victim of an attack could hit back.

Prospective martial-arts students should visit several venues before getting started, according to the nonprofit U.S. Martial Arts Association, based near Sacramento, Calif. Commercial schools generally require a financial commitment: Contracts of one year, similar to fitness clubs, are typical, as are rates of about $75 a month. But price doesn’t guarantee quality, the association says, and newcomers may find their best choice through a church recreation program at a relative bargain.

Carl Feind, a 52-year-old cardiologist who takes aikido lessons twice a week in Magnolia, Miss., endorses the hard martial arts as being good for the heart. “I have been in classes with several people in their 60s. In aikido, we spend a lot of time practicing to survive falls. Picking yourself up off the mat 30 or 40 times isn’t a bad aerobic workout.”

To be sure, injuries are common in martial arts, even in younger participants. A George Washington University study in 2003 found one injury per 48 hours of martial-arts practice. The sport with the closest comparable rate in the study: rugby, which includes tackling. At the other end of the risk spectrum: tennis, with one injury per 1,400 hours of play.

Bob McKenna, a 64-year-old lawyer in Denver, says his tae kwon do workouts have taken a toll: a broken nose, broken arm and some cracked ribs. But Mr. McKenna, who started training in his late 20s, says all those injuries were decades ago. As he has aged, both he and his instructors have gradually reduced the intensity of his routines.

Tamer Kicks

“These days if I tried to do some of the flying kicks, I’d be hurt,” he says. “Older people should stay within our physical limits.”

Still, those limitations may allow for impressive displays. At age 74, Karsten Joehnk can still kick at a level even with the top of his head: 5 feet, 8 inches. The semiretired real-estate investor, who lives in La Jolla, Calif., says that in a recent proficiency test at his school, Pacific Karate, he broke through two 1-inch pine boards held together by his instructor as a target.

Triumphant as that kick may seem, it left Mr. Joehnk disappointed. “Last year I broke three boards,” he says. Looking forward to his next try in a few months, he adds, “I’ll break three again.”

Corrections & Amplifications

Aikido was misspelled as akido in this article.