I never understood the describing of an over-powered automobile as a "muscle-car". I owned a 1965 Ford Mustang when I graduated from Portage Northern High School, it was the version with the bigger engine, but, I put "baby moons" on it and drove it like a pussycat. The term "muscle car" might have originated from the vision of a tattooed over-sized bicep masturbating a stick shift through the gears as his tires smoked and his engine roared, but I don't think so.
A muscle-boat is a boat you row or paddle. Muscle transportation in general would be something human or horse-powered...not a hunk of metal and plastic that is artificially and chemically propelled from point A to point B. A gas-powered unit could be called a "racket-rocket" or "horseless carriage" or a cancer-spewing coffin on wheels. Of course, I am most interested in the muscle transportation energy one derives from food. "Support your local farmer, ride a bicycle". Treat your loved-ones and neighbors like you want them to live cancer-free forever....use your muscles, or your horse for transportation.
Oh well, what's done is done, we've been spewing carcinogens for over one hundred years in the name of speed and convenience, but not in the name of efficiency. We work half of our lives away to support the "happy motoring" lifestyle...and the "muscle-car" guys must spend two-thirds of the working hours supporting their habit and boosting their macho self-image, subsequently scaring and bullying the gentle folk along their path.