Boutique fitness gets new muscle

Increasingly specialized exercise centers cater to time-pressed urban elite

Live DJs, disco lights and screaming crowds make it seem as if it's a wild nightclub. The exercise bikes betray the illusion. They reveal it's actually a spinning club - a manifestation of the trend in which a proliferation of boutique establishments focus on only one fitness activity.

Such specialized exercise centers' popularity is growing, even though memberships can cost five times as much as gyms'.