Paul Kienitz, owner of Riverside Athletic club, began his gym business as the Fitness Force in 1981. At that time the location was a medium sized former garage in downtown Merrill. The gym consisted of twelve Nautilus machines and one exercise bike. As things progressed, the Fitness Force was able to add group exercise classes, tanning, bring in several more bikes, and open a second Fitness Force in Wausau.
As the business grew, a new location and a larger building were needed. The current site at 500 South Center Avenue was constructed and opened in 1989. The new building was given the name Riverside Athletic Club, Inc. Expansion of the original building in 1996 brought a gymnasium, balcony workout area, a laundry/storage room, and added and Studio 500 as a tenant.
A second expansion in 2002 added the aquatic center, pool locker rooms, an expanded personal coaching area, new Endless Summer Tan Center, and updated the reception and lobby areas. This expansion also brought another tenant, a massage therapist.
In 2011, Riverside Athletic Club again expanded its business to meet the needs of the community by bringing a facelift to the gymnasium by adding Artificial Turf to half of the gym as well as new equipment to be used in various programs.
In 2015 and 2016 Riverside wanted to address the needs of a larger demographics by adding more functional training equipment to its facility. This expansion brought the addition of several new pieces of equipment and a new Functional Training Area that is available 24 Hours a day.
Today Riverside Athletic Club covers just less than 30,000 square feet and is the home of various run Boot Camps, Group Exercise Classes, Mini Muscles Gymnastics and houses the following small business tenants: Studio 500, Weight Watchers, In Touch Massage Therapy and Presence of Balance Massage LLC.