To investigate the effect of increasing velocity within one gait on horse and rider movement and to describe the resulting changes in saddle forces, seven ridden dressage horses were examined on an instrumented treadmill. The speed ranged between 1.3-1.8 m/s at walk and 2.6-3.6 m/s at trot. Kinematics of the horse and rider, vertical ground reaction forces and saddle forces were measured simultaneously. Velocity dependency of each variable was assessed for the whole group with linear regression. With increasing velocity, the saddle forces at walk were mainly influenced by the accentuated rocking type of movement and at trot by the higher vertical dynamic and a more rigid horseback which resulted in increased counteracting force between horse and rider. Even small increases of velocity changed the dynamics of the movement pattern of the horse and consequently the forces emerging beneath the saddle: a 10% increase within the indicated speed range resulted in +5% (walk) and +14% (trot) higher total saddle force peaks. Accurate comparison of saddle forces requires speed-matched trials; velocity is therefore a factor which also has to be considered under clinical conditions.