Ladder Climbing: a Dynamic Biomechanical Model and Ergonomic Analysis (Slip, Fall, Overexertion, Heights).

Accidents from slips, falls and overexertion during climbing activities frequently result in injuries. Little research, however, has been performed in this area. A dynamic biomechanical model of the ladder climbing activity was developed. The inputs are: (1) subject joint locations, (2) h and and foot separation, (3) anthropometry, and (4) rung forces. The outputs are: (1) joint moments and (2) compressive and shear forces at the L5/S1. Ten male subjects were tested under combinations of rung separation, ladder slant, climbing speed and climbing direction. The joint moments estimated by the model were validated using principles of internal consistency. The estimated back forces were validated through a comparison of the torso muscle IEMG activity to the model-predicted torso muscle forces. The validation study also generated safety and biomechanical design guidelines relating to the affect of task, equipment and user parameters on h and and foot forces, h and torque, and h and and foot separation. The validation results indicate that the biomechanical model may be used to predict joint moments during the climbing activity. The model appears to significantly underpredict the compressive and shear forces at the L5/S1 level. This may be due to the highly dynamic and asymmetric nature of the climbing activity and the tendency for body stability and support requirements to generate antagonist torso muscle activity and drive the torso muscles to contract at higher levels than predicted by the optimization model. Under the conditions studied there does not appear to be a significant slip hazard for people with no previous musculoskeletal problems, artificial joints or other pathology. Under field conditions there may be a potential for climber grip strength to be exceeded, and foot-slip potential to exist during the use of vertical ladders. There is also the potential for localized muscle fatigue at the elbow, hip and ankle during long climbs. The relatively high measured torso IEMG activity suggests that a ladder climbing activity may generate considerable compressive and shear force at the L5/S1 disc.PhDIndustrial engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161210/1/8702688.pd