Differences in motor variability among individuals performing a standardized short-cycle manual task.
Motor variability (MV) has been suggested to be a determinant of the risk for developing musculoskeletal disorders in repetitive work. In this study we examined whether individuals consistently differed in the extent of motor variability when performing a standardized short-cycle manual task. On three separate days, arm kinematics was recorded in 14 healthy subjects performing a pipetting task, transferring liquid from a pick-up tube to eight target tubes with a cycle time of 2.8s. Cycle-to-cycle standard deviations (SD) of a large selection of shoulder and elbow kinematic variables, were processed using principal component analysis (PCA). Thereafter, between-subjects and between-days (within-subject) variance components were calculated using a random effects model for each of four extracted principal components. The results showed that MV differed consistently between subjects (95% confidence intervals of the between-subjects variances did not include zero) and that subjects differed consistently in MV between days. Thus, our results support the notion that MV may be a consistent personal trait, even though further research is needed to verify whether individuals rank consistently in MV even across tasks. If so, MV may be a candidate determinant of the risk of developing fatigue and musculoskeletal disorders in repetitive occupational work.
Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, SE-901 87 Umeå, Sweden; Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden. Electronic address: jonas.sandlund@umu.se.
Jonas
J
Sandlund
Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden. Electronic address: sdivya1@vt.edu.
Divya
D
Srinivasan
Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden. Electronic address: marina.heiden@hig.se.
Marina
M
Heiden
Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden. Electronic address: svenderik.mathiassen@hig.se.
Svend Erik
SE
Mathiassen
D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D004550:Elbow / Q000502:physiology; D004551:Elbow Joint; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D025341:Principal Component Analysis; D011597:Psychomotor Performance / Q000502:physiology*; D012016:Reference Values; D012782:Shoulder / Q000502:physiology; D013239:Stereotyped Behavior / Q000502:physiology*
Between-subjects variability; Day-to-day variability; Individual differences; Kinematics; Principal component analysis; Repetitive task