The right approach depends on your organizations broader objectives and what your looking to achieve by setting up a website. The first question I’d ask is ‘what purpose the site is going to serve?’
The answer to that question (and a number of others) will determine the approach.
If a website ends up being the right decision then I’d suggest a simple platform like http://www.squarespace.com – it’s very easy to set up and update with a reasonable subscription fee.
However, if budgets are tight and you’re looking to grow your reach then an alternative strategy might be to simply use Facebook to create a community of interest around your fitness offering with links out to google docs/sheets/slides for deeper content, e.g. fitness program schedules etc.
Happy to help further if you’re able to provide further clarification.