With no way for consumers to get fitness services online, the health club industry has proven immune to Amazon.com’s increasing dominance in retail.

Studio chains like Planet Fitness Inc. (PLNT), Soul Cycle and Pure Barre are thriving in a retail industry that is overall declining, with bankruptcies and store closures amid sliding sales as consumers invest more in online shopping. (See also: U.S. Retail Sales Slid in March.)

The fitness industry is “a sector that’s not being hurt by Amazon, which is the key,” Randal Konik, a Jefferies analyst, told eMarketer Retail.

The number of health clubs in the U.S. has increased every year since 2005 to about 36,540 clubs this year, a 36 percent increase in the past 12 years, according to International Health, Racquet & Sportsclub Association data cited by eMarketer. Last year, revenue in the U.S. health club industry increased about 7 percent to $27.6 billion from the year prior and, with only about 19 percent of Americans having a health club membership, the fitness industry has ample room for growth.

Planet Fitness, which offers $20-per-month memberships, is among the chains riding high on growth. The Newington, N.H.-based club has had 10 years of consecutive quarterly same-store sales gains. Same-store sales were up about 11 percent in the fourth quarter from a year prior. Planet Fitness stock is up 2 percent year to date, and up 20 percent the past year.

“We have greater conviction in the industry's bright trajectory," Konik said. “Industry dynamics remain compelling … Health/wellness is a [long-term] trend. No longer are club memberships solely in the hands of affluent households." 

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