This study investigates the kinematic features of unrestrained vertical arm movements using a three-dimensional tracking system called Selspot. Movements between point targets were analyzed under varying conditions of speed and hand-held load. Unlike previous studies that emphasized straight hand paths, this research found that hand paths could be curved. However, all movements, whether curved or straight, showed an invariant tangential velocity profile when normalized for speed and distance. This invariance is interpreted as a simplification of the underlying arm dynamics. The study also examined the effects of different loads and gravity on arm trajectories. It found that the tangential velocity profile remained invariant across different speeds and loads, suggesting that the motor system uses a consistent planning strategy regardless of movement conditions. The results indicate that the hand's trajectory is primarily influenced by external constraints rather than internal joint-level planning. The study compared the kinematics of vertical and horizontal arm movements, finding that vertical movements showed more curvature and were influenced by gravity. The results suggest that the motor system adapts to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The findings support the idea that the motor system uses a hand-level planning strategy, which is consistent with the minimum-jerk model of movement. The study also examined the effects of load on movement, finding that the tangential velocity profile remained invariant across different loads. This suggests that the motor system can adjust to different loads without changing the velocity profile, indicating a consistent planning strategy. The results also show that the motor system can adapt to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The study found that the tangential velocity profile is invariant across different movement conditions, suggesting that the motor system uses a consistent planning strategy regardless of movement conditions. The results indicate that the motor system adapts to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The findings support the idea that the motor system uses a hand-level planning strategy, which is consistent with the minimum-jerk model of movement.This study investigates the kinematic features of unrestrained vertical arm movements using a three-dimensional tracking system called Selspot. Movements between point targets were analyzed under varying conditions of speed and hand-held load. Unlike previous studies that emphasized straight hand paths, this research found that hand paths could be curved. However, all movements, whether curved or straight, showed an invariant tangential velocity profile when normalized for speed and distance. This invariance is interpreted as a simplification of the underlying arm dynamics. The study also examined the effects of different loads and gravity on arm trajectories. It found that the tangential velocity profile remained invariant across different speeds and loads, suggesting that the motor system uses a consistent planning strategy regardless of movement conditions. The results indicate that the hand's trajectory is primarily influenced by external constraints rather than internal joint-level planning. The study compared the kinematics of vertical and horizontal arm movements, finding that vertical movements showed more curvature and were influenced by gravity. The results suggest that the motor system adapts to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The findings support the idea that the motor system uses a hand-level planning strategy, which is consistent with the minimum-jerk model of movement. The study also examined the effects of load on movement, finding that the tangential velocity profile remained invariant across different loads. This suggests that the motor system can adjust to different loads without changing the velocity profile, indicating a consistent planning strategy. The results also show that the motor system can adapt to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The study found that the tangential velocity profile is invariant across different movement conditions, suggesting that the motor system uses a consistent planning strategy regardless of movement conditions. The results indicate that the motor system adapts to different movement conditions by adjusting the trajectory's shape and speed, but maintains a consistent velocity profile. The findings support the idea that the motor system uses a hand-level planning strategy, which is consistent with the minimum-jerk model of movement.