http://www.nytimes.com/2010/03/04/business/retirementspecial/04GYM.html; Written by John Hanc, In America's Gyms, More Than a Touch of Gray, The New York Times, March 3, 2010.
1) International Health, Racquet and Sportsclub Association conducted the survey.
2) Because IHRSA represents the nations health clubs tallying over 30,000 I would assume that they would help to sponsor the research.
3) The managers of the clubs would definitely have an interest in knowing the age groups of the people that are continually coming to use the gym. They are now designing their gyms to everything from special work-out machines and exercizes to the choice of music, in order to target the correct age group of their costomers.
4) Yes the sample included, adults over the age of 55. There are 30,022 health facilities. It states that the surveys are collected annually.
5) The results are stated as followed; "membership among adults 55 and older rose to 10.5 million in 2008, from 1.5 million in 1987, making this group the fastest-growing segment of the health club population"
6) There are no graphs included in this article from the New York Times.