Reasons for performing study: In the equestrian world it is assumed that riders use changes in weight distribution and leg forces as important instruments to give horses directions about speed and direction of movement. However, the changes of these forces have never been quantified. Objectives: To investigate the distribution of normal forces (perpendicular to surface) underneath the saddle and of normal forces exerted by the rider's legs during lateral movements. Materials and methods: Eleven riders performed 3 different exercises: riding straight ahead, shoulder-in and travers at trot. Three saddle force systems were used simultaneously. The magnitudes of the forces were summed for the total area, the inside and the outside half of the saddle and inside and outside leg. Mean and maximum summed forces were analysed statistically. Results: The saddle forces showed a rhythmic pattern but leg forces were more irregular. Mean total saddle force was lower (P = 0.006) when riding straight ahead (671 ± 143 N) than when riding shoulder-in (707 ± 150 N) or travers (726 ± 165 N). Mean inside saddle force was higher (P = 0.003) when riding travers (468 ± 151 N) than when riding straight on (425 ± 121 N) or shoulder-in (413 ± 136 N). Maximum outside leg force was higher (P = 0.013) when riding travers (47.2 ± 33.9 N) than when riding straight on (31.6 ± 24.1 N) or shoulder-in (34.2 ± 27.3 N). Conclusion: The study helps to give a biomechanical background to well established but intuitive horse riding techniques.