What fitness gear and equipment is actually on topic?
One important category of equipment that would be off topic are bicycles, because they have their dedicated site.
So we should assume, every fitness equipment that doesn't have a dedicated site is on topic?
How does it translate to water sports? SUPs or kayaks will probably raise no eyebrow, but there are bigger water sport 'gadgets' like yachts...
If the question is about a product review, or similar, then it would be off topic. Bicycles could be on topic here, as could other questions that relate to items that have their own stack. Questions that involve bicycles could be on topic here, sports or bicycles. Possibly even travel, etc., depending on the question.
If the question is primarily about how to use said item in a fitness program, or identification of a piece of equipment, it's on topic here. If it is about technical support ("how do I replace the motor in a treadmill?" "What is this thing my bike chain is connected to?") then it will probably be migrated or closed.
So pretty much any fitness gear, equipment, applications, etc., can be on topic as long as the context is the use of said object in a fitness program.
