SoulCycle: Are you a believer?

It’s 5 p.m. on a Friday night, and while much of San Francisco is relaxing over cocktails at happy hour, 50 fitness fanatics are cooped up in a small, dark room in the Castro with thumping music, and pedaling stationary bicycles as if their lives depend on it.

In a sense, they do.

Devotees of SoulCycle, an indoor bicycling chain, say there’s more to the 45-minute workout than burning thighs and high heart rates — they get a dose of spirituality and community, too.

Part marketing and part mantra, the “soul” in SoulCycle refers not to soul music but to a rider’s immaterial essence. With its motivational wall messages (“athlete,” “legend,” “warrior,” “renegade,” “rock star”) and teachers who shout affirmations during class (“You are stronger than you know!”), it’s no wonder that the class I’m at — led by lithe former dancer Ian McAndrew — is referred to by riders as “the Church of Ian.”

“I could pay for one hour of therapy, or go to five SoulCycle classes,” said Matthew Yazzie, 36, a San Francisco startup executive, who rides three times a week. “Whenever you get in a zone with any kind of exercise or anything you’re really into, it can be really meditative. Any good sort of religion teaches you to look inside and to really focus on yourself, and that’s definitely something you do a lot of in class.”

Created in New York in 2006 by Elizabeth Cutler, a former real estate agent, and Julie Rice, a talent manager, SoulCycle takes spinning — grueling sessions on an indoor bike, a staple of traditional gyms for two decades now — and freshens it up for a new era.

Instead of the weathered road cyclist who typically leads spin classes, SoulCycle’s instructors are perky, if not youthful. No meters are used to calculate watts and RPMs; SoulCycle’s focus is on pedaling extra fast in time to nightclub music — with dance moves and weight lifting thrown in for good measure. Its classes are held in the dark, by candlelight — you can barely see your neighbor, let alone compare yourself to him or her. The conditions are cramped and hot, but that’s a positive in SoulCycle’s view. It adds to the intensity of cycling, which you’re not really doing alone (they say) but together, with a common goal.

“At a gym you’re left on your own to do what you want to do,” said Nathan Friedman, 38, a San Francisco advertising agency owner who has given up all other forms of exercise for the past 18 months. “Here you’re doing it as a team, like a pack. It’s encouraged to get to know (fellow riders) a little more than just walking past them in the locker room.”

SoulCycle is growing fast: In 2006, it had one studio; today, there are 45 in eight states, five of them in the Bay Area in the past two years. SoulCycle Castro opened June 25. (In 2011 SoulCycle formed a strategic partnership with Equinox to help fund its expansion.) While some loosely call it a cult for its strong appeal, it’s not alone in its ascendance on the sports scene.

Nationwide, the number of gyms and fitness clubs is on the rise, increasing from 29,890 in 2010 to 34,460 in 2014. So are the ranks of health club members, growing from 50.1 million in 2010 to 54 million in 2014, according to the International Health, Racquet & Sportsclub Association, or IHRSA, in Boston.

Boutique studios are a new trend, sought by clients who seek personalized attention and small group classes in boxing, yoga, pilates, barre and other sports, according to Meredith Poppler, an IHRSA spokeswoman. They’re easier to open than large gyms because they cost less to rent, equip and run. (Clients paying by the class don’t get locked into committing to monthly gym fees, either.)

Bay Area SoulCycle fans include former Twitter CEO Dick Costolo, 52, Wired Editor in Chief Scott Dadich, 39, and Lisa Sugar, 38, founder of PopSugar, as well as concierge company owner Grace Rosenthal, 31, of Los Gatos, and Ziba Zojaji, 34, a stay-at-home mom in San Jose.

“It’s a great stress reliever, especially since it’s high intensity,” said Costolo, who enjoys running and CrossFit, too. “It’s not like you can be thinking about work while you’re doing that.”

Truer words were never spoken.

The night I take McAndrew’s class, I’m wishing I hadn’t taken a session at the Palo Alto branch on Monday and a similarly strenuous class on Thursday at Revelry Indoor Cycling & Fitness in San Mateo, which opened in October (and has become a social hub on Third Avenue). It’s not because the classes weren’t fun. My muscles are running on empty.

SoulCycle studios feature the clean scent of Jonathan Adler grapefruit candles; white, gray and yellow decor; and a communal locker area for changing shoes (cycling shoes are rented for $3) and stowing gear (lockers boast iPhone charging stations). Each studio has a bathroom or two and a shower or two — not the kind of place to linger.

Clients book the $30 sessions online, in advance. Dadich tips me off to scheduling smartphone alerts on Mondays at 11:59 a.m. because classes with popular teachers like McAndrew sell out minutes after registration opens at noon. (No-shows who don’t cancel by 5 p.m. the previous day are charged full price.)

Our smiles evaporate as class begins. For the next 45 minutes, we’re taken through an arc of agony by McAndrew, whose Byronic good looks and commanding stage presence make it ever so slightly more bearable. We sit and pedal, stand and pedal, our feet circling in double time to the music — sprints, hills and more. We tap our rears on the back of the seat, do push-ups on the handlebars and increase the resistance with a turn of the knob at his command. Toward the end, we grab 2-pound weights from under our seats and do curls, presses and boxing — all while cycling. I take a towel to my face, dripping with sweat, hoping it will be over soon.

Philip Wilson, an associate professor of kinesiology at Brock University in Ontario, Canada, has studied exercise motivation for 15 years and says there are two factors that get people exercising: controlling motives — based in guilt or shame, which come from external sources and cause anxiety and negative feelings about their bodies; and autonomous motives — freely chosen, consistent with the person’s values, and which spur long-term adherence to activities the person finds enjoyable.

The people who gravitate to SoulCycle appear to be people who have similar ideas about what’s valuable and fun — torturous rides in a hot, crowded room, and the physical and mental outcomes achieved by doing so.

Wilson hasn’t studied SoulCycle specifically (there are none in Canada), but he speculates that the lure for clients lies in the psychological concept of relatedness. That jibes with the sense of community its clients report.

“People want to feel meaningfully connected to others in their environment,” Wilson said. “It’s not belongingness, but it’s similar. As human beings, we have this innate need to feel connected to other human beings.”

After the class, I’m wiped out, dreaming of collapsing at home over a glass of wine, but Mia Mora, 38, a tech sales strategist who played soccer in college, says she feels great.

“I guess what keeps me coming back is it’s the best workout ever,” she says. “I leave exhausted and energized at the same time.”

Spinning out of control

Silicon Valley personal trainer Pattie Lindquist, who specializes in injury prevention, offers these tips for spinning for long-term health:

Riders should not pedal without tension, whether seated or standing. Having some tension on pedal ensures control of your hips and knees. This avoids shearing or tearing of the meniscus (cartilage that allows your knee to glide smoothly). First-timers are usually guilty of this.

Performing upper-body movements while sitting upright and pedaling requires extra care. Maintain a neutral neck position (ears in line with shoulders) for correct form at the same time. Otherwise, “I see that as a potential injury for the neck,” she says..

Small spaces can make for a hot workout. We like to think that heavy sweating makes a great workout. But it’s your work output (effort) that burns the calories, not the heat alone! Drink plenty of water, cool down and stretch after class so your body recovers safely.

— C.Z.

SoulCyle by the numbers

34,460: Number of gyms and fitness studios in the U.S. in 2014

45: Number of SoulCycle studios in the U.S.

12,000: Number of SoulCycle riders each day

11 & 78: Youngest and oldest SoulCycle riders

$30: Cost of a SoulCycle class

$2,200: Cost of a SoulCycle spin bike

50: Number of bikes in a SoulCycle class

500-700: Calories burned in one SoulCycle class

321 million: Current U.S population

54 million: Number of health club members in the U.S. in 2014

82.7 million: Number of Americans who do not exercise at all

Sources: SoulCycle, International Health, Racquet & Sportsclub Association, Physical Activity Council, www.census.gov .