Boston — Health club membership in the United States increased by 3 percent last year from 42.7 million members (over the age of six) in 2006 to 44.1 million in 2007, according to early estimates from an annual tracking study by the International Health, Racquet & Sportsclub Association (IHRSA).

In addition, industry revenues increased by 5 percent to $18.5 billion, the study shows. This growth in health club membership represents an increase of more than 115 percent in 10 years, while growth in total revenues represents an increase of 127 percent.

The data, which appears in IHRSA's annual membership report, Profiles of Success 2007, indicates that clubs have also improved upon membership retention from 2005 to 2006 by three percentage points, increasing from 70 percent to 73 percent. Simultaneously, participating IHRSA clubs raised total revenue per member by nearly 5.5 percent in 2006 to $741.80.

In April of last year, IHRSA reported that memberships for 2006 increased by more than 3 percent from 41.3 million in 2005 to 42.7 million in 2006.