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Willie Nelson looks as comfortable in a gym as he does on stage–his waist-length braid sways as he pummels a speed bag and throws punches at his longtime tae kwon do instructor.

Yes, that’s the Red-Headed Stranger, and all this toe-dancing and fist-flinging is for good reason: It’s a tuneup for his starring role in the film “Life Is a Hoss.” Shooting of the Western/martial arts film starts in September.

Nelson, though, doesn’t need a movie to motivate him to stay fit. He has always worked exercise into his life, whether he was on the road or off, and he says he couldn’t keep up his touring pace if he didn’t exercise.

“I have to go do something every day or every other day or my muscles curse me,” he says. “If I didn’t work to keep in good shape, I couldn’t do what I do.”

Nelson, who turns 73 on April 30, is a regular jogger. He loves to golf. He makes time to practice his martial arts forms even while on the road.

Punching it up

Thus a not-exactly-inconspicuous taupe tour bus rolls into an Austin strip mall just after lunch on a recent day, and out trots Willie wearing a pair of black gym shorts, T-shirt and worn sneakers.

“That’s the singing grandpa,” 8-year-old Shora Um gasps as Nelson strolls into her father’s new Gym Kick & Box. Master Sam Um has trained Nelson for the last decade. Two years ago Nelson earned a black belt in tae kwon do, the Korean art of self-defense, from Um.

Today, Um is putting the singer through the paces to make sure he’ll be ready for the movie. Nelson climbs onto an exercise machine, testing out some of the new pneumatic weight-lifting equipment. Sweat beads up on his forehead, evidence, perhaps, that the red bandanna’s not just a fashion statement.

“Keep your chest on it; you want to go light today,” Um says as Nelson starts pumping. “Don’t forget to breathe.”

After working his way down a row of machines against one wall, Nelson heads across the room to where he really feels at home–in front of the punching bags. He takes a swipe at the double-end ball, which simulates the movements of a boxing opponent. This could be handy for the upcoming movie scenes in which he has to take on former boxer Randy “Tex” Cobb.

Soon, Um suggests the speed bag. Nelson dons a pair of red gloves and punches the melon-sized, tear-shaped bag alongside Um, who gives tips. Then Um picks up a pair of black padded shields and invites Nelson to whale away. He does.

When Um asks Nelson, “How are your kicks?” the country crooner responds by whirling around, letting fly with a roundhouse that connects with the shield the instructor is holding. Then they move to a tall blue bag hanging from the ceiling. Nelson spots the bag with his eye, turns, then kicks like a donkey.

“I haven’t done this in a while; I’m sweating a little,” he confesses. “Between now and September I hope to do a lot of days here.”

A stress-reliever

You might wonder how Nelson crams exercise into his schedule. But to hear him tell it, the only real work he does is a couple of hours of singing most evenings–leaving “22 hours to kill.” Because exercise makes him feel good, he tries to fill some of that time by working out.

Nelson has always been into physical fitness (never mind that he’s never made a secret of his pot-smoking habit). In high school he played basketball, baseball and football and ran track. “It goes back to Charles Atlas,” Nelson says of the strongman who in 1922 was proclaimed “The World’s Most Perfectly Developed Man.” Atlas went on to head a successful mail-order fitness course. Nelson always admired him.

That respect grew into a consciousness that physical activity was necessary to keep up his hectic music life: Nelson has recorded more than 200 albums and still tours regularly.

Exercise “reduces stress, and stress is the biggest killer on the planet,” Nelson says. He started instruction in kung fu, a Chinese form of martial arts, in Nashville in the 1980s and wanted to continue martial arts instruction in Texas.

“My kids and wife went to classes with Master Um, and they kept telling me about it,” he says. “Since the boys were growing up, I wanted to be able to keep up with them.”

Nelson started training in tae kwon do with Um several times a week, in group and private lessons. He hasn’t been as regular with Um lately; he spends a lot of his off time in Maui with his wife, Annie, and their teenage boys Luke and Micah.

Um says Nelson has tried more than once to persuade him to fly out and meet him on the road for some tae kwon do sessions. So far Um has stayed put, although sometimes he critiques videos of the singer practicing his martial arts forms.

“He’s very well-disciplined,” Um says. “Our classes are very hard.”

On the road again

Exercise session over, Nelson walks out to his tour bus. Inside, he passes a flat-screen TV (tuned to CNN) and the kitchenette, where a bowl of apples, kiwi, peaches, bananas and grapes shares space with two bottles of mescal.

He’s here to show off the speed bag that’s attached to the ceiling in his bedroom. He takes a few whacks at it, to demonstrate. Yes, he says, he can use the bag while the bus is rolling. And yes, he has fallen down in the process. That doesn’t keep him from trying.

He sticks to a simple philosophy when it comes to exercise.

“I do what I feel like doing,” he says. “I don’t have a rigid plan. If I don’t feel like running, I’ll do kicks. Each day is a little different, so I don’t get bored. I try to mix it up.”

The singer doesn’t think it’ll take much extra training to get ready for the movie. The foundation is there; he just needs to stay in practice. “If I can just sustain where I am, I think I’ll be OK,” he says.

When asked to demonstrate his signature martial arts move, he leaps up, shouts, “I’ll be right back!” and spins 360 degrees, arms poised to strike.

It’s a formidable sight, in a weird, pigtail-flinging, bare-kneed way.