Sudden loading during a dynamic lifting task: a simulation study.
It is believed that nurses risk the development of back pain as a consequence of sudden loadings during tasks in which they are handling patients. Forward dynamics simulations of sudden loads (applied to the arms) during dynamic lifting tasks were performed on a two-dimensional whole-body model. Loads were in the range of -80 kg to 80 kg, with the initial load being 20 kg. Loading the arm downwards with less than that which equals a mass of 20 kg did not change the compressive forces on the spine when compared to a normal lifting motion with a 20 kg mass in the hands. However when larger loads (40 kg to 80 kg extra in the hands) were simulated, the compressive forces exceeded 13,000 N (above 3400 N is generally considered a risk factor). Loading upwards led to a decrease in the compressive forces but to a larger backwards velocity at the end of the movement. In the present study, it was possible to simulate a fast lifting motion. The results showed that when loading the arms downwards with a force that equals 40 kg or more, the spine was severely compressed. When loading in the opposite direction (unloading), the spine was not compressed more than during a normal lifting motion. In practical terms, this indicates that if a nursing aide tries to catch a patient who is falling, large compressive forces are applied to the spine.
Andersen
T Bull
TB
Institute of Medical Anatomy C, University of Copenhagen, Denmark. tbull@idraet.au.dk
Simonsen
E B
EB
D000222:Adaptation, Physiological / Q000502:physiology; D001415:Back / Q000502:physiology*; D003198:Computer Simulation; D006801:Humans; D017770:Lifting; D035002:Lower Extremity / Q000502:physiology*; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology*