title: On time relation between erector spinae muscle activity and force development during initial isometric stage of back lifts.
abstract: Models available for the prediction of the compressive forces acting on the lumbar spine during lifting do not consider the relaxation of back muscles in the stooped posture that possibly remains at the very beginning of pulling force development. This study aimed at examining back muscle activity during the initial stage of back lifts, i.e. under isometric conditions, in order to obtain the time relation between the back muscle activity and the forces developed. A biomechanical model was used for the prediction of the compressive and shear forces acting on the third lumbar disc at the very beginning of back muscle activity. The temporal pattern of myoelectric activity of the muscles examined exhibited large intra- and interindividual variation. On several occasions in the four healthy cases studied, mechanical activity of the back muscles started when some pulling force on the lifted burden was developed.
authors.affiliation: Department of Occupational Hygiene, Central Institute for Occupational Medicine of the German Democratic Republic, Berlin, DDR.
authors.forename: B
authors.initials: B
authors.lastname: Hirn
authors.forename: H
authors.initials: H
authors.lastname: Seidel