Abstract Originating from an ancient Hawaiian tradition Stand Up Paddle Surfing (SUP) is a growing pastime and sports activity in which a person stands upright on a surfboard and propels it using a single paddle. It is expected that SUP is an ideal full-body workout for amateurs as several muscle groups are required for the paddling motion. Therefore measurements of muscular activity of eight subjects were executed during on-water and treadmill-trials using wireless surface electromyography (sEMG). sEMG of 16 muscles of the trunk plus video data were acquired at three different paddling speeds. The results showed that all measured muscles of the trunk were activated and that their activity can be allocated to the different paddle-stroke phases. The study proved that although the paddle stroke is mostly performed through upper extremity activation, also the trunk as well as the hip and knee stabilizer generate power and show high muscular activation.