Moving your body/muscles is how you move the lymph fluid around your body. The lymph system is the system that is the sewer drain that brings cellular waster to be recycled or eliminated, but theres no heart providing pressure to move the fluid, body movement is mainly what does it. So that means exercise, stretching, massage. Not sure why they think this is a new thing, its well-known already.
Make me think the authors may have an interest in a gym company, or were paid to write it this way.