Almost 1,100,000 adult consumers in the Delaware Valley belong to a fitness club. These memberships bring in close to $1.9 billion in sales to local gym owners.

January is critical for the small business owners that operate gyms in the Philadelphia area. According to the International Health, Racquet, and Sportsclub Association, this one month alone, accounts for 10.8% of annual membership sales. New Year's resolutions are the reason for this early year spike.

To capture a larger share of the $209-million local consumers  will spend on gym memberships in January, requires fitness center owners to advertise. The best way to do this is on Philadelphia radio. Here's why.