Practice-related changes in lumbar loading during rapid voluntary pulls made while standing

Citation
Ah. Chang et al., Practice-related changes in lumbar loading during rapid voluntary pulls made while standing, CLIN BIOMEC, 15(10), 2000, pp. 726-734
Citations number
37
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Ortopedics, Rehabilitation & Sport Medicine
Journal title
CLINICAL BIOMECHANICS
ISSN journal
0268-0033 → ACNP
Volume
15
Issue
10
Year of publication
2000
Pages
726 - 734
Database
ISI
SICI code
0268-0033(200012)15:10<726:PCILLD>2.0.ZU;2-X
Abstract
Objective: To determine if five days of practice on a novel dynamic, multi- joint pulling task resulted in lower magnitudes of lumbar loading or a more consistent relationship between pulling force and lumbar loading. Design. A repeated measures design compared how practice influenced the mag nitude of lumbar torque and the correlations between lumbar torque and pull ing force. Background Previous studies suggest that practice can decrease the magnitud e of lumbar loading on simple manual material handling tasks, but it is unk nown whether practice reduces lumbar loading for more complex tasks. Neithe r is it known whether the consistency of lumbar loading increases with prac tice. Methods. Ten healthy adults practiced impulse-like horizontal pulls to targ ets equaling 20% 40% and 80% of their estimated maximal dynamic pulling for ce over 5 days. Movements were unrestrained, other than keeping the feet fl at on the ground. We used a four-segment, sagittal plane inverse dynamics m odel to compute lumbar, hip, knee, and ankle torques on days 1 and 5 from g round reaction forces and moments, pulling forces, and kinematics. Results. An analysis of variance showed significant practice-related change s in lumbar torque at the time of peak pulling force (lumbar torque(peakPF) ). The lumbar torque(peakPF) decreased for the 20% pulls, did not change fo r the 40% pulls, and increased for the 80% pulls. Two subjects showed a sig nificant decrease in lumbar torque(peakPF) for all three force levels, Coef ficients of determination between pulling force and lumbar torque (r(PF.per pendicular to tau)(2): a measure of the consistency of the relationship bet ween these two variables) were significantly higher on day 5 than day 1. Conclusions. Practice on a novel pulling task changed the magnitude of lumb ar torques and increased their correlation with pulling force, suggesting t hat subjects learned strategies that improve motor control of lumbar torque s.