The waves were flat at Ocean Beach, but Brian Bennett paddled out anyway. For Bennett, a surfer of 20 years, it didn't matter that he might not catch a single wave on this crisp sunny afternoon with no other surfers in sight. Surfing is what the 34-year-old ad salesman does for exercise.
"It's good to feel the electricity in the water," he said. "It's like taking a couple energy drinks. I'm up, I'm alert and I'm a happier person."
It's not just the meditative mind trip that gets surfers in the water. Some die-hards are loath to admit it, but the sport's health benefits are many.
Sinewy shoulders. Washboard abs. Improved cardiovascular health.
Dedicated surfers accidentally build physiques that health-club acolytes would trade their memberships for.
For most surfers, though, the reason for surfing is surfing itself, said Dr. Mark Renneker, an associate professor of family and community medicine at the University of California, San Francisco. The 54-year-old Renneker should know; he's a renowned big-wave rider himself.
"It's not a sport to them at all--it's a way of life," he said. "It's salubrious up the wazoo. You can't find anything that makes you as healthy."
Renneker frequently recommends surfing to non-surfers to treat high blood pressure, repetitive strain injuries and chemical addictions.
But the biggest benefit, he said, is cardiovascular.
Renneker said a surfer's heart rate can recover from intense activity as quickly as that of a triathlete, because of the focus on controlled breathing. He says asthmatics have also experienced improved respiratory functioning, and the sport's meditative effects can reduce stress even in the most anxious patients.
"It really is leaving the world, as it were, on land, and losing yourself in the rhythms of the ocean," he said. "And that has been the draw of surfing since the beginning. And then to have a really physical training...to really progress you have to surf three times a week."
But it can also be dangerous.
Lance Harriman, 36, a surfer of nearly three decades and a San Francisco physical therapist, said top riders often limp into his practice with blown-out knees, shoulders and ankles.
Poor paddling technique can cause upper-body strain, and the water can be unforgiving to joints on big-wave wipeouts, Harriman said.
Many longtime surfers suffer from a shared malady: so-called "surfer's ear" that develops when bone grows in the ear canal from repeated wind and water irritation, especially in colder climates. The surgery involves removing the bone.
But surfers are usually ferociously eager to get back on their boards.
"The fiends take this seriously," Harriman said. "You dangle the carrot in front of them--and that's getting back in the water--and they work hard. Sometimes too hard."
Harriman said many injuries can be prevented by simple stretching and strengthening exercises and attention to proper technique. Offseason cross-training for underused lower-body muscles also helps.
But some longtime surfers scoff at the idea of injecting traditional sports training into a soulful, spur-of-the-moment passion.
Big-wave riders have always trained with breath-holding and strengthening exercises to survive tumbles from tall waves, but surfing's full-body workout is usually adequate for most others, said Bob Wise, 58, owner of Wise Surfboards in San Francisco.
"I can tell a guy's been surfing a lot when he walks through the door," he said. "They don't have much leg muscle usually...But they're broad in the shoulders. They're lean. You can't eat that much when you're out on the water three or four hours a day. You can just tell."
Wise has tried yoga to loosen a back stiffened from years of surfing and water-skiing.
But the "best part about it was when it was over," he said, adding that he doubts younger surfers will ever stop to stretch as they're charging toward the beach.
"The kids aren't going to accept that. They're not into serenity," Wise said. "You paddle out and you don't have to worry about North Korea firing missiles for an hour. You've got your own thing going. You've got a wave to catch."