But how about the woman stepping sideways with two big rubber bands encircling her thighs? The one hopping in a sand pit, from one end to the other? The man kneeling precariously on a big inflated ball, hefty dumbbells in each hand, bowing to and fro? And what's with that woman shifting a heavy ball from side to side as she takes long, deep steps forward — while balancing on a low wooden beam?

All are part of a normal day at Zum, Peter Shmock's long-awaited new health club in Belltown.

For many years, Shmock has been one of the most intriguing fitness folks in town. His open, diverse approach to training grew out of experience both mainstream and alternative. A shot-putter on the 1976 and 1980 U.S. Olympics teams, he was director of strength and conditioning with the Mariners for 11 years. He draws from not only weight lifting, circuit training and endurance conditioning, but also agility and explosiveness drills, tai chi, yoga and relaxation and awareness practice. He's trained dancers at Pacific Northwest Ballet, basketball players with the Seattle Storm, golf and football pros, and regular Joes.

Over the years, I've mentioned Shmock several times in this column, for injury-prevention advice for softball players, his Outdoor Gym classes at local parks, his book on training with weighted balls, his physical and mental sessions with high-school athletes. He designed a "No Time? No Excuses!" exercise program for our annual fitness issue two years ago.

Yet it's not a given that such an eclectic approach can be transferred into a health club. Can Shmock blend familiar equipment and training techniques with the more uncommon? Find trainers who understand his vision and are able to convey it as he has? Entice members game to try it? And enough of them to make the club self-sustaining?

Early signs at Zum (pronounced "zoom"), which opened May 1, seem promising.

The building itself is unusual for a club, 1930s-era brick, formerly the longtime home to, appropriately, American Games (whose new showroom for game-room equipment has moved a block away). Though a bit imposing from the outside, painted a dark charcoal, with metal "ZUM" sign and wide entry doors, inside the 8,000 square feet are both refined and industrial, serene and vibrant. Rough brick walls, unpainted wood ceiling and heavy support beams overhead are offset by plenty of light, from frosted plate-glass windows on three walls, track lighting on overhead beams and a long, narrow skylight on the broad roof.

After lobby and locker rooms, the main floor becomes one large, open, workout area. A long matted section can be set off with tall canvas curtains for group classes, but otherwise each space flows into others.

Uncommon club equipment catches the eye: a 5-by-15-foot sand pit, climbing rope, gymnastics rings, low balance beams, steel bars for climbing or stretching and, sprinkled throughout, big inflated fitness balls and perhaps the largest collection of weight balls in town — 35 by my count.

Even the more typical apparatus has twists: handsome gray TechnoGym weight machines; unpainted steel free-weight benches; downright pretty Uesaka dumbbells, with rotating handles and beveled edges; bright yellow LeMond RevMasters for group cycling classes, gathered below a large projection screen with ongoing slide and video shows. Pilates equipment fills one corner. A water fountain anchors a central break area with granite and rhyolite boulders for chairs and chalkboard-painted walls that open in four directions.

Up a narrow set of stairs to a mezzanine, the cardio room (with stair-climbers, stationary bicycles and elliptical machines) looks over the main floor. Up other steps is an all-white "quiet room" for yoga, stretching and "tuning in." A small Zen rock garden rests at its far end.

Of course, the proof is in the training. The comment Shmock has heard most often so far: "It's like a playground for adults."

Members can use Zum like any club, doing their own workout programs or attending group classes. But membership — high-end at $600 initiation and $125 monthly for an individual — includes two one-hour evaluations up front and monthly half-hour tune-ups with a trainer.

"We ask what they want to do and how they want to feel," Shmock says. Resulting programs emphasize coordinating and integrating muscle groups instead of isolating them, and paying attention to posture, alignment and safety.

"This gym is perfect for someone who really wants to get fit," says Paula Tobol, 37, of Seattle, who was a trainer herself for 10 years and now is senior marketing manager for Deloitte & Touche. "They have the best trainers, awesome equipment, a nice facility — it's really one of the best gyms I've been in — and it's not intimidating." That last point helped her talk a friend who'd never belonged to a gym into joining. "She loves it, she's lost weight, and she's happy."

Shmock has specific plans for even more equipment, but in a sense, he says, the club remains unfinished.

"I don't know which direction it will go."

Zum is at the southwest corner of Fifth Avenue and Bell Street in Seattle, 2235 Fifth Ave.; 206-443-3933; www.clubzum.com.