Your idiom for treadmill is probably tapete de corrida, literally in English mat of running or mat for running. The translation system you used probably only translates one word if you enter several, and it most likely does not recognize idiomatic groups of words. Try passadeira motorizada and you probably won't get treadmill either, but somethin
Thanks for your comment. But I finally found the word I was looking for when Grammar Geek sent me a site in which there is a picture of the gymnastics device I' d like to know its name in English. There the site all the time refers to it as a "treadmill', and not as a "mat" .