Including figures in your paintings can sometimes be tricky, especially with action figures, so you need to get out and find reference material whenever you can. Maybe the Olympic Games is too remote for many of us, but the wide variety of sports, some fast-moving, some at a much slower pace, give us ample opportunities for capturing a sense of the moving figure.
Attending events around the country where people are actively engaged in perhaps a county show, some sport or other form of activity, however bizarre, is another excellent way of getting material for your paintings. A little bit of colour, as in this view of the annual Llanllufni beach head-ball games, goes a long way, and competitors get into some fascinating positions, often head-butting each other as well as the ball. Having to work so quickly does sharpen your sketching skills, and sometimes I find myself drawing so quickly that the images often overlap each other. That isn't really a problem, though, as with a sketch you are not trying to produce a finished work of art.
While understanding the rules of the game is not really vital for the artist, having an affinity with your subject is definitely an advantage, for example, if you are sketching boats with complicated rigging, or perhaps the actions and image of a combined harvester in operation - but there again, it does depend on how close you are to the action.