What would they gain by lying to people about the relative efficiency of marathon runners versus race walkers, or ways to burn more energy when walking? How would those lies (if lies) lead to more sales for them (that's the only benefit I can imagine)?
It's basic scrutiny of an article. If a company primarily sells fitness watches, publishing articles on fitness will net them sales, whether it's true or not. The incentive to be correct isn't there, unlike more rigorous sources of information.
It's the same reason you shouldn't blindly believe the marketing words on the back of a box of cereal.
What? If a fitness company started posting absolute bullshit like "vaccines hurt running performance," I think that would reflect poorly on them and cause them to lose sales. I wear a fitness watch similar to a Polar and would abandon my brand if they started espousing health pseudoscience.