Control That Maximizes Movement Speed 1 1 2 Multi-component Control Strategy Underlying Production of Maximal Hand Velocity 3 during Horizontal Arm Swing 4 5 6 Control That Maximizes Movement Speed 2

27 Movement control responsible for generation of maximal hand velocity was 28 studied on the example of horizontal arm swing that is a component of various sports 29 activities. The movement was performed with the non-dominant arm in similarity with 30 the baseball bat swing. The task was to generate maximum hand velocity at a target. The 31 movement included trunk long-axis rotation and horizontal shoulder and elbow extension. 32 Kinematics and torque analyses were performed to study the organization of fastest 33 movements and to compare trials representing the best and worst performance in each 34 subject. Results revealed complex control strategy, with the trunk, shoulder, and elbow 35 playing unique roles in generation of maximal hand velocity. The trunk provided crucial 36 contribution, directly, rotating the entire arm, and indirectly, exerting interaction torque 37 that caused swift elbow extension. The major role of the shoulder was to transfer the 38 mechanical effect of trunk motion to the elbow. However, the shoulder became the 39 primary motion generator when the trunk reached its limits of rotation, revealing 40 sequential organization of control. The role of the elbow was to maximally comply with 41 passive influence of proximal joints. The findings are discussed in light of the leading 42 joint hypothesis that offers a straightforward interpretation of control of horizontal arm 43 swing as well as practically efficient recommendations for increases in movement speed. 44 The revealed role of inter-segmental dynamics in production of high movement speed 45 suggests that movement slowness characteristic for some motor disorders may be 46 partially a compensatory strategy that facilitates regulation of interaction torque. 47