“With the baby boomers' impact on demography, people older than 55 make up the fastest-growing segment of the fitness industry, and more gyms are adding programming especially for them. In places where hip-hop once blasted as buff bodies hefted weights, a grayer clientele is signing up for yoga and aquatics classes or exercising on recumbent bicycles and elliptical machines designed for older bodies. ‘It's a natural trend as this segment of the population ages,’ said Joe Moore, chief executive of the International Health, Racquet and Sportsclub Association. ‘We're seeing many [seniors] going to health clubs because of the health benefits and not just the aesthetics of looking better.’ The association estimates that there were nearly 10 million health club members older than 55 in 2007, up from 2 million in 1990. Nearly a third of the member clubs now have senior programming. Locally, gyms have added classes such as ballroom dancing in the past two years to attract seniors, and Sport & Health Club offers one called ‘Fall Proof,’ a fall-prevention workout. David von Storch, the owner of hip Vida Fitness, which has opened three luxury fitness clubs in the District in the past three years, kept seniors in mind when designing the facilities, adding workout studios with softer lighting and flooring, and endless pools at each location for joint therapy and recovery.