How can we suggest movement in our images? How long should the movement be? It’s up to you!
Plenty of scope here, you could try a long exposure to blur the motion and blur the subject but you may need a tripod to keep the background sharp. Alternatively try panning to freeze the subject whilst blurring the background. Conversely, use a high shutter speed to freeze the action at a critical point. You might even try multiple exposures and capture a sequence of shots.
You will find some examples here.