HARTSDALE, NY — Americans have been fitness-conscious for some time, but they may be beginning to get active about it.

According to the 17th annual SUPERSTUDY of sports participation by American Sports Data Inc. (ASD), 54.9 million people engaged in a single fitness activity on at least 100 occasions. While this measurement includes the new genre of “Mind-Body” exercise (and is, therefore, not comparable with prior estimates), “same-sport” comparisons indicate an overall increase in frequent exercise.

A consistent finding of studies conducted by ASD in 1996, 1998 and 2002 is that more than 80 percent of the adult population pays homage to the idea of physical fitness, while only one in five gets enough exercise, a fraction that — due to nullifying gains and losses in a range of fitness activities [and despite continually rising health club memberships] — has remained constant over the years, ASD said.

The study projected 39.4 million health club members — an increase of 8.6 percent over the previous year. While part of the increase is attributable to statistical variation, substantial membership growth is supported by independent data, according to ASD, citing a nationwide compilation of Yellow Pages listings by InfoUSA shows 23,497 clubs as of Jan. 1, 2004 — an increase of 16 percent over the prior year tally of 20,207, according to ASD.

“Seventy percent of all Yellow Pages listings are bona fide commercial health clubs — not YMCAs, gymnastics studios or personal trainers — and this increment of more than 3,000 new facilities accounts for a good portion of several million additional club members,” said ASD president Harvey Lauer. “A modest growth rate of 4 percent among pre-existing clubs could account for the remainder.”

Other findings:

  • As a flagship of the mind-body fitness movement, Pilates is the “hottest” growth trend, according to the report. With 9.5 million participants in 2003, participation has grown by 103 percent in just the past year, and by 445 percent from its initial measurement of 1.7 million in 1998-89 percent of those practitioners are female.

  • Elliptical motion trainers continue on an upward trajectory, garnering 13.4 million participants in 2003, up 25 percent for the year, and 247 percent since 1998.

  • With an average age of 43.5 and 48.3 for frequent participants (100+ days), recumbent cycling is the second “eldest” exercise activity — trailing fitness walking in participant longevity.

  • The compound measurement of yoga/Tai Chi claimed 13.4 million adherents in 2003, a growth rate of 20 percent for the current year, and 134 percent since 1998.

  • Treadmill exercise, the largest single physical fitness activity has slowed to lumbering, but inexorable single-digit growth. With 45.6 million participants in 2003 — up only 5 percent in the past year, but that's still a 937 percent climb from the base of 4.4 million recorded at the study's inception in 1987.

  • Strength training is another giant, which lately never disappoints; year after year, it continues to deliver single-digit growth. In 2003, there were a projected 51.6 million individuals in the United States who trained with some form of free weights — an increase of 25 percent over 1998. Thirty million used weight/resistance machines, up 33 percent from 1998.