One of these type of shops just opened down the street from where I live in central Lausanne. I had to check the name of it on my way home today (because I honestly can't say I've had the occasion to go in there): it's called Moovement Sports Nutrition, and it's located at the corner of Rue du Tunnel and Place du Tunnel. (
map) Strangely, I just tried to find a website for the shop to reference, but the only thing I can find in Switzerland that uses the name Moovement is a male stripper service based in Geneva...
Anywho, I think this shop is probably what you're looking for. The windows are lined with many large assorted bottles that are filled with what I assume to be various sorts of protein/nutritional supplements (names like VoluMass, etc.), and there are also posters up and a big-screen TV displaying images of men with muscles that Jeremy Clarkson would describe as 'writhing like a sack of pythons'. A large selection of spandex clothing is also available.
Bus stop is Tunnel, number 5 bus from the central train station heading in the direction of Epalinges, and also number 6 (Praz-Sechaud) or 8 (Bellevaux) from the centre of town. If coming by car, you can park in Place du Tunnel itself.
Heather