Owners Chantel and Mark Knox said there had always been a big demand for a gym in the town but it skyrocketed when they moved into the extended Cromwell Swim Centre building on Barry Ave.
Mr and Mrs Knox, both 26, said it had been hard work establishing Cromwell's only public gym, although the venture was starting to pay off after years of 15-hour days.
"It's been a challenge being a young woman in business. I often get asked if the manager is around and for a while every employee was older than me. But it has been good and we have had a lot of support from the community and our business mentor," Mrs Knox said.
The gym's ratio of members to population is above the national average and the facility has a good retention rate.
"When people join here they stay with us and use the gym a lot more, instead of just joining and never turning up," she said.
Cromwell's demographic has not eluded the savvy couple who cater to the town's older population by offering special fitness packages.
"Our average membership age is quite high so we have things like Silver Sneakers for over 60s and try to include classes which cater to those members as well. Cromwell people are very active anyway and the gym's a base for all the outdoor activities people do in the area," Mrs Knox said.
With the gym's growth also came the ability to expand its payroll and about 10 part-time employees enabled Mr and Mrs Knox to resume a "semi-normal" working life.
"For the first year of business I was here every hour the gym was open, from about 5.30am to 8.30pm. We had to live at mum's house as well and on our only afternoon off, on a Sunday, we would sleep," Mrs Knox said.
The couple moved from Dunedin to Cromwell in 2006 with the idea of establishing a gym in the area, despite a lack of suitable rental spaces.
Mr Knox said at the time just two appropriate buildings were available and both were tucked away in the town's industrial sector.
Business steadily grew at the McNulty Rd facility over two years, with the help of small-town behaviour.
"We put a lot down to word-of-mouth and positive feedback. We also both love sport and are involved in a lot of community teams so it is easy for us to cater to what people in that sort of group want," Mrs Knox said.
The couple plan to continue expanding their business, which will include a Stirling Sports franchise for Mark to manage soon.
"We think the growth will continue. Cromwell's on the way up," Mrs Knox said.