The rule of gaze / space linked with the direction of subject that you shooting in movement. For example, you are taking the photo of a person who is biking. This rule says that you should leave more space in front of the person than behind though his direction. It is the same in some situation as animals or cars in movement. According to common idea of people, making this composition in photo gives the imagination of movement immediately.

When taking a portrait of a person, if the subject is facing away from the camera rather than straight into the lens, it is preferable to leave more empty space in the direction in which they are looking rather than in the area right behind them. This rule can even be used for things that aren’t moving and aren’t really looking. For example, if you were to take a picture of a flower, you might notice that the blossom seems to “face” in a certain direction. In the same way, if you were to take a picture of a person, it would be preferable to have more space in front of the person than behind them.to have more space in the direction in which they are looking, rather than behind them.