The objectives were to compare sagittal plane posture of the pelvis, trunk and head of elite dressage riders when they ride actively to train the horse versus sitting passively and following the horses’ movements at trot, and to evaluate the effects of these changes in rider posture on load distribution on the horse’s back. Synchronised motion capture and saddle mat data of seven elite dressage riders were used to measure minimal and maximal angles and range of motion (ROM) for the pelvic, trunk and head segments, the angle between pelvis and trunk segments, phase-shift between pitching motions of pelvis and trunk, and pelvic translation relative to the saddle. Non-parametric statistical tests compared variables between the two rider postures. In the passive rider posture the pelvis, trunk and head showed two pitching cycles per stride. Maximal posterior and anterior pelvic rotation occurred, respectively, early and late in the horse’s diagonal stance phase. Compared with pelvic movements, trunk movements were slightly delayed and head movements were out-of-phase. In the active rider posture the pelvis and trunk pitched further posteriorly throughout the stride. Most of the riders showed similar sagittal plane movements of the axial body segments but with some notable individual variations.