Ideally you and/or your team members have direct experience in the fitness business. If so, highlight this experience and expertise. But also highlight any experience that you think will help your business succeed.
If your team is lacking, consider assembling an advisory board. An advisory board would include 2 to 8 individuals who would act like mentors to your business. They would help answer questions and provide strategic guidance. If needed, look for advisory board members with experience in gyms and/or successfully running a small businesses.