title: Reciprocal influences on performances of a postural-suprapostural task by manipulating the level of task-load.
abstract: The objective of this study was to investigate the reciprocal influences of stance pattern (bilateral stance vs. unilateral stance) and thumb-index precision grip task (static target vs. dynamic target) on postural-suprapostural tasks by manipulating task-load. Fifteen healthy volunteers participated in four postural-suprapostural tasks, including static force-matching in bilateral/unilateral stance (BS_static; US_static), dynamic force-matching in bilateral/unilateral stance (BS_dynamic; US_dynamic), and two control tasks in bilateral and unilateral stances without a finger task. The normalized force error (NFE), reaction time (RT) of the finger tasks, and normalized change in center of pressure sway (Delta NCoP) were measured. For suprapostural task performance, a significant interaction effect between postural and suprapostural tasks on NFE of the finger tasks was noted (static: BS<US; dynamic: BS>US), but RT was not different among the four tasks. For postural task performance, negative Delta NCoP during unilateral stance indicated a spontaneous reduction in postural sway due to added force-matching. In contrast, addition of force-matching tended to increase postural sway during bilateral stance, but postural fluctuations decreased as task-load of suprapostural task increased (BS_dynamic<BS_static). In conclusion, performance of postural-suprapostural tasks was differently modulated by task-load increment. Our observations favored adaptive resource-sharing and implicit expansion of resource capacity for a postural task with a motor suprapostural goal.
authors.affiliation: Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Cheng-Ya
authors.initials: CY
authors.lastname: Huang
authors.forename: Rong-Ju
authors.initials: RJ
authors.lastname: Cherng
authors.forename: Ing-Shiou
authors.initials: IS
authors.lastname: Hwang
mesh_terms: D000328:Adult; D025461:Feedback, Physiological / Q000502:physiology; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D013647:Task Performance and Analysis; D016474:Weight-Bearing / Q000502:physiology*