Reid Inouye can talk a blue streak when the subject turns to standup paddling and the way it changed him. In three months, he lost 35 pounds and dropped four pants sizes. The 51-year-old surf industry entrepreneur feels like a kid again.

There's even a little spring in his instep — and that's the strangest part of his new fitness routine.

"I used to be flat-footed, and that went away," Inouye said. "The muscles in my feet are so much stronger than they used to be. I have arches now. It is the weirdest thing. It is built up, and there is an inch and a half of support in my foot. I never knew you could build up muscles in your feet."

OK, so no one starts working out to get great feet. But who can argue with a good foundation?

"You are pushing off with your feet a lot, and it goes up to your thighs and your core," he said. "It's a really good cross-training workout for any sport. It works your core, it works your bottom, and it works your arms."

When Inouye first tried standup paddling last fall, he knew right away that he was hooked. The hybrid sport, which combines surfing and paddling, eliminated the neck and back pain he had endured for years.

His first workout was a long-distance paddle from Hawai'i Kai to Kahala. It left him exhausted — and exhilarated.

"Now I am out there every day for an hour," he said. "An hour of this is like two to three hours of surfing."

But Inouye, who has surfed since he was a teenager, rarely uses his traditional equipment anymore. With standup paddling, he can combine a workout with the pleasures of catching waves. Or he can simply paddle.

He's felt so good doing it that he ditched his running habit of 15 years.

"I started burning calories a lot faster, so I said, 'Why do I need to run?' " Inouye said. "And it is not like I am working at it. When you run three times a week or go to the gym, you are working. When you are doing this, you are having fun."

Until last month, Inouye was a fixture on the Hawai'i surf contest scene, promoting events for the past 25 years. He plans to spend more time editing his surfing publication Heavywater Magazine and to create a new magazine devoted to standup paddling.

But Inouye also turned his new passion into a business, creating a school for novice standup paddlers called Paddle Core Fitness.

"I think it is a good way to get people to do workouts in the water," he said. "People are looking for alternatives to the gym. I have taken people on paddle workouts on flat water and they have had a great time. I have taken kids, senior citizens and college baseball coaches."

Inouye opened the school in mid-October and takes clients to the protected waters of Ala Moana Beach or to Hale'iwa Harbor. They've been drawn to the sweat, not the surf.

"This is cardio," he said. "This is the gym. This is everything in one."

Reach Mike Gordon at mgordon@honoluluadvertiser.com.

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