Muscle bike or Musclebike are kids 20" bicycles or 16" front wheel styled after Dragster's & Muscle Car's from the mid 60's to early 70's. Bananna seat & sissy bar for bucket seat & roll bar, rear slick,, sginal light's, console shifter, even some with wheelie bar.
Raleigh Chopper is a Muscle Bike with a chopped front fork & 16" wheel, not Chopper with an extended front fork. You can not properly define a motercycle as a muscle bike. A muscle bike is not a low rider.
Sport bike's looks with cruiser's drivetrain. usually a v-twin engine. Does not rev to high RPM like kawasaki bikes. Strong, fast bikes with good performance.
some muscle bikes are . . .Ducati: Monster. Suzuki: VS650, VX800. Triumph: Speed Triple.