Today, it is very important to evaluate fatigue symptoms in young adults. The subjective symptoms index (SSI) has been widely used to evaluate fatigue, but it was developed to evaluate fatigue in laborers and has various associated problems. Therefore we developed a new subjective fatigue scale (SFS-Y) consisting of 24 items, to evaluate fatigue in young adults. The purpose of this study was to clarify the features of the SFS-Y and compare them with those of the SSI.Both instruments were administered to 595 students aged 15-20 yr, and the main results obtained were as follows. The SFS-Y has more items related to mental fatigue and measures fatigue parameters that are different from those of the SSI. Also the SFS-Y has more sub-scales than the SSI and is a better multiple evaluator, including evaluations of gender differences. Although both the SFS-Y and SSI have acceptable levels of reliability, that of the SFS-Y is somewhat higher. Furthermore, the SFS-Y can better measure slight changes in subjective symptoms of fatigue occurring during daily activity. These observations suggest that the SFS-Y is effective as a measure of subjective fatigue symptoms in young adults.
Objectibe: To understand the neural mechanisms of motor imagery, we examined differences in cortical excitability (primary motor cortex) induced by motor imagery between highly skilled and less skilled exponents of Kendo (Japanese fencing). Methods: First, to confirm differences in Kendo skills between the highly skilled and less skilled Kendoists, EMGs from four muscles (two intrinsic and two forearm muscles) and grip forces on the left and right sides were recorded simultaneously while performing Kendo. Second, to investigate changes in excitability of the motor cortex induced by motor imagery, motor evoked potentials (MEPs) in response to transcranial magnetic stimulation (TMS) were recorded from the left and right first dorsal interosseous (FDI), abductor digiti minimi (ADM), extensor carpi radialis (ECR) and flexor carpi radialis (FCR) muscles. During motor imagery of Kendo skills, MEPs were recorded under the following three conditions: (1) The subjects imaged Menuchi-movements (hitting the head with a bamboo sword) without a visual aid (V^- ), (2) the subjects imaged Menuchi-movements with the aid of a video system (V^+), (3) the subjects imaged the maximum muscle contraction of each of the four muscles, related to Menuchi-movements, respectively. Results: During motor imagery of Menuchi-movements under condition V^-, MEP amplitudes were larger in the highly skilled Kendoists than those in the less skilled Kendoists. Moreover, MEP amplitudes in the less skilled Kendoists were larger under condition V^+ than under condition V^-, whereas the opposite was true in the highly skilled Kendoists although the defference did not attain statistical significance. In both sets of subjects, however, the MEP amplitudes during motor imagery of individual muscle contraction were the same, i.e., the differences in MEP amplitude between the highly skilled and less skilled Kendoists disappeared. Conclusion: The brain function for imaging motor skills differs between highly skilled and less skilled Kendoists. That is, the motor imagery of highly skilled Kendoists invdves performing concrete movement (internal imagery) whereas that of less skilled Kendoists involves looking at the movement (external imagery).
We conducted a practical study on the process of movement correction in sprint running from the standpoint of sports morphology. The subject was an elite Japanese female sprinter attending university. Running movement was analyzed by self-observation and outside-observation through impression analysis. The coach had discussions with the athlete to achieve new movement and an ideal running movement, and were able to reach a common understanding. During the process of movement correction, the athlete and the coach needed to share and empathize the movement sensation. The athlete and the coach shared four stages of movement correction, and went through the four stages using sprint drills, similar to movement and sprint running at 80% subjective effort. The coach felt that the series of movements had become much smoother from the third stage. Similarly, the movement sensation experienced by the athlete improved after correction of the running motion. Furthermore, the athlete achieved a feeling of weighting on the contact leg and improved foward motion after movement correction.