The effect is due to combining flash and ambient light on a moving subject. The flash illuminates the subject which then moves. The subject blocks the ambient light creating a silhouette, and then moves before the flash fires so that the image lit by the flash is offset with the silhouette, giving the hard cartoon outline effect. No photoshop required for this one!
In this case first curtain sync was used, meaning the flash fired before the ambient exposure, which is why the black outline occurs "ahead" of the subject. If second curtain sync was used the shadow would appear to behind the subject in a more "chronological" order.