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この論文は国立情報学研究所の電子図書館事業により電子化されました。

The lateral body weight-shifting task is used in a typical therapeutic program for patients with orthopedic complaints or hemiparesis, and is considered effective in helping patients recover from asymmetric weight distribution in affected and unaffected lower limbs during bipedal standing. This study examined the effects of fundamental features, such as central tendency effects, lateral differences, and light touch support by the upper limbs on performance accuracy in the lateral body weight-shifting task. In Experiment 1, the features of performance in lateral body weight-shifting were examined for patients with orthopedic complaints (N = 11) compared with age-matched elderly healthy participants (N = 11). They were asked to accurately load one or two thirds of their body weight on a target (affected and unaffected for the patients and the left and right for the healthy participants) lower limb. They were allowed to use light touch support by placing their upper limbs/hands on horizontal parallel bars during the task. The accuracy of task performance was examined with constant error (CE), variable error (VE), root mean squared error (RMSE), and coefficient of intra-trial variation (CV). The features of the task specific to the patients with orthopedic complaints appeared in RMSE, which showed that the RMSE scores were larger when they loaded the two-third of the body weight than when they loaded one-third on the affected lower limb. Furthermore, the load on upper limbs was smaller for the patients with orthopedic complaints than that for the age-matched healthy participants. The results of CE scores showed biasing errors of both overshooting the one-third target load and undershooting the two-thirds target load, which indicated central tendency effect, in both the patients with orthopedic complaints and healthy participants. Therefore, the central tendency effects may well occur in lateral body weight-shifting for both patients with orthopedic complaints and healthy people in common. Experiment 2 examined the fundamental feature of central tendency effects, which may occur in common with patients and healthy people, in relation to lateral differences and light touch support by the upper limbs in lateral body weight-shifting, testing healthy participants. Forty right-handed and -footed participants were assign to one of two groups differing in the use of support by the upper limbs; the support group (N = 24) and the no support group (N = 16). For the support group alone, the mean CE score indicated an undershooting (i.e., a relative or partial central tendency effect) and the mean RMSE score indicated lateral differences. The mean CV score for the support group was smaller than that for the no support group, indicating a benefit of the use of support by the upper limbs for performance stability. Experiment 3 examined the effects of the support by upper limbs on task performance, particularly the feature of central tendency effects, in lateral body weight-shifting in healthy participants (N = 23). To this end, the relationships between the respective loads on the upper and lower limbs during body weight-shifting were examined in terms of correlation analyses. This showed that the participants often used reciprocal interlimb weight-adjustment between the upper and lower limbs. Furthermore, correlation analyses showed that the reciprocal imterlimb weight-adjustment correlated both with the degree of overshooting at the condition of one-third target load and with the degree of undershooting at the condition of two-thirds target load. To summarize, the features of the patients with orthopedic complaints and the fundamental feature in common to both the patients with orthopedic complaints and the healthy participants were shown in Experiments 1 to 3. First, the central tendency effects generally occurred in lateral body weight-shifting. Performance accuracy of the patients with orthopedic complaints showed an undershooting when the relatively heavy amount of the body weight was loaded on the affected lower limb. Second, the support by upper limbs had both positive (stable task performances) and negative (large undershooting) effects on performance accuracy of lateral body weight-shifting. Finally, the reciprocal interlimb weight-adjustment correlated with the degree of overshooting and undershooting in lateral body weight-shifting., 首都大学東京, 2013-09-30, 博士（健康科学）, 乙第88号