Title page for ETD etd-03032009-041004
|Type of Document
||Johnson, Christian Axel
||Optimization-based biomechanical evaluation of isometric exertions on a brake wheel
||Master of Science
||Industrial and Systems Engineering
|Woldstad, Jeffery C.
|Kroemer, Karl H. E.
|Price, Dennis L.
|Date of Defense
Low-back pain and injury claims account for a large number of occupational
illnesses each year. In the railroad industry, many maintenance and operation activities
require a high degree of manual labor, often resulting in increased stress on the lowback.
One of the most common functions of railroad yardmen is the setting and releasing
of railcar hand brakes. A static three-dimensional low-back biomechanical model was
developed to estimate the levels of compressive force on the L3/L4 spinal joint that
existed in subjects during an experiment that simulated the hand brake setting task. We
recorded three-dimensional body posture and resultant forces at the hands for analysis by
the model. The model resolved the external forces acting on the body to a resultant
moment about L3/L4 and then employed an optimization algorithm to estimate the
internal lumbar muscle forces generated to resist the external forces. The muscle forces
and external forces were added to arrive at a prediction of compressive force at L3/L4.
The experiment investigated the effects of general body posture, left hand grip,
subject anthropometry, and hand brake torque level upon predicted compressive force at
L3/L4. An analysis of variance revealed that compressive force was significantly
affected by each of the experimental variables. Additional analyses at subjects' maximum
voluntary torque levels indicated that compressive force would exceed NIOSH guidelines
for low-back compressive force, especially in males. Predicted L3/L4 compressive force
at maximum torque ranged from an average of 2350N in small females to an average of
7485N for large males. We then used regression analysis to predict brake torque levels
that would cause compressive force to exceed the NIOSH (1981) recommended
maximum of 3400N. Based on the prediction methods used, hand brake torques of 40 to
80 Nm would be likely to cause compressive force to exceed this maximum.
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