In the present study, the relations of simple reaction times of right and left hands with muscle powers of right and left hands, back, and leg were examined. Hand preference was assessed by the modified Edinburgh Handedness Inventory. Measurements for reaction time were taken using the Newtest 2000 Reaction Time Apparatus. Takei Kiki Kogyo Dynamometers were used in measuring the muscle power of the subjects (0-100 kg). The simple reaction time (SRT) for right hand was not correlated with right and left hand and leg. The left hand SRT was significantly negatively correlated with right and left hand and leg powers. The choice RT was significantly correlated with right and left hand powers, but not leg power. There were no right-left differences in simple RT and hand power. These results suggest that sport activities are associated with eye-hand visual reaction time (VRT) and visuospatial intelligence (VSI). Exercise's positive effect may be associated with especially the right brain or left hand.