In the present study, we investigate laterality effects on motor learning based on motor imagery workout. Four adult groups that were mentally and physically right handed performed reaching movement via upper and non-upper hand with speed and accuracy as possible. Before and after training session the movement time has recorded and analyzed. Results showed that mental and physical practices through similar learning processes (similar exponentially learning curves), have positive effect on both hand performance. But in comparison with mental imagery, motion time in post-test session became significant for both hands after physical practice. More importantly, in comparison with motor imagery with non-upper hand, mental imagery with upper hand leads to wider progress in motor speed. This kind of advances did not show up in control group. Findings of this study show priority of upper hand in motor learning via mental workout.