Continued Motor Imagery Strategies Focusing on Numerical Information as well as Imagery Content Alter Spinal Motor Nerve Function and Motor Skills

[Purpose] The effects of continued motor imagery as a voluntary practice on the excitability of spinal motor nerve function and motor accuracy were examined. [Participants and Methods] Nine healthy subjects practiced motor imagery focused on numerical information for four weeks. F-waves were derived from the left thumb ball during resting trials and motor imagery trials in the first and fourth weeks. After each trial, a pinch force adjustment task was given to assess motor accuracy. [Results] No difference in the F/M amplitudes’ ratio was observed between the trials in the first and fourth weeks, and no change in motor accuracy was observed before and after the motor imagery trials. However, two subjects with large absolute errors in pinch force values in the first week improved their motor skills before the motor imagery trial in the fourth week. [Conclusion] The results of this four-week continuous numerical imagery intervention suggest that motor skills can be improved if there is room for improvement in motor skills.