Image: The public is getting more health-conscious

US health club industry revenue reached US$21.4bn (17bn euro, £14bn) as memberships totaled 51.4 million in 2011, according to figures from International Health, Racquet & Sportsclub Association (IHRSA) and market research company IBISWorld's Gym.

IHRSA's data shows that the size of the US industry is still growing - the total number of health clubs across the country has increased from 26,830 in 2009 to 29,960 in 2011.

According to a separate report by IBISWorld's Gym, the growth is likely to continue as the demand for gyms and health and fitness clubs is expected to rise over the next five years.

The report said: "Demand for gyms and health and fitness clubs will continue to rise over the next five years, as the general public becomes more health-conscious and the aging population places a greater emphasis on staying fit.

"In particular, growth in household incomes will positively affect businesses, leading operators to expand into larger facilities."