Self-Selected Manual Lifting Technique: Functional Consequences of the Interjoint Coordination

The pattern of movement self-selected by 39 subjects to lift light loads from 9 cm above the ground is described in kinematic and electromyographic terms. Hamstring length changes were estimated from hip and knee angular kinematics. Subjects adopted a posture at the start of the lift intermediate be...

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Bibliographic Details
Published in:Human factors 1995-06, Vol.37 (2), p.395-411
Main Authors: Burgess-Limerick, Robin, Abernethy, Bruce, Neal, Robert J., Kippers, Vaughan
Format: Article
Language:English
Subjects:
Adult
Analysis of Variance
Biological and medical sciences
Coordination
Electromyography
Ergonomics. Human factors
Female
Fundamental and applied biological sciences. Psychology
Hip
Hoisting
Human mechanics
Humans
Joints - physiology
Kinematics
Knee
Lifting
Lifting and carrying
Lumbar Vertebrae - physiology
Male
Manual lifting
Motor ability
Muscle, Skeletal - physiology
Muscles
Occupational psychology
Physiological aspects
Postural Balance - physiology
Posture
Psychology. Psychoanalysis. Psychiatry
Psychology. Psychophysiology
Space life sciences
Task Performance and Analysis
Vertebrae
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Summary:The pattern of movement self-selected by 39 subjects to lift light loads from 9 cm above the ground is described in kinematic and electromyographic terms. Hamstring length changes were estimated from hip and knee angular kinematics. Subjects adopted a posture at the start of the lift intermediate between stoop and full-squat postures. A consistent coordination between knee, hip, and lumbar vertebral joints during lifting was described through calculation of the relative phase between adjacent joints and found to be exaggerated with increases in load mass. During the early phase of lifting, knee extension leads hip extension, which in turn leads extension of the lumbar vertebral joints. Early in the lifting movement, when load acceleration is greatest, the erectores spinae are thus relatively long and shortening slowly. Both of these factors produce greater back extensor strength. Rapid hamstring shortening is also delayed, which enhances their strength, and coactivation of the monoarticular knee extensors and biarticular hamstrings observed early in the lifting movement suggested that the knee extensors contribute to hip extension through a tendinous action of the hamstrings.
ISSN:0018-7208
1547-8181
DOI:10.1518/001872095779064537