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Abstract
Climbing a vertical ladder continues to be a safety concern for both manufacturer and professional users. Among these professional users are the "wind service technicians" who climb the wind towers greater than 80m to perform a variety of maintenance work (BLS, 2010). These technicians are getting injured at a frequent rate (USPC, 2011). Among these, musculoskeletal injuries associated with the knee joint are dominant (Reid & McMulin, 2006).
Published literature on ladder climbing has mainly addressed the accidents related to slips and falls (Armstrong, 2009; McInyere, 1983; Dewar, 1977) and a few studies have addressed the musculoskeletal injuries associated with slanted ladders (Hoozemans & Louche, 2005; Bloswick, 1990). Currently a gap in the literature exists with respect to the potential risk of musculoskeletal injuries associated with vertical ladder climbing. That is the aim of this study, to predict the lower limb internal joint forces and moments during a vertical ladder climbing activity and associate the outcome of this analysis to the causes of musculoskeletal injuries.
Six male and six female adult subjects participated in this study. Participants climbed an instrumented vertical laboratory ladder similar to ladders used on wind towers. Independent variables for this experiment included three levels of climbing speed, two levels of climbing direction, three levels of rung separation, three levels of subject anthropometry and two levels of gender. Dependent measures included measured hand and foot forces, predicted lower and upper joint moments and EMG activity of the lower limb flexor and extensor muscles.
Synchronized kinetic and kinematic data collected during the experimental trials was provided to a two-dimensional dynamic link-segment model. The output from the model included the predicted internal forces and moments at the ankle, knee and hip joint.
Results indicated climbing style, climbing speed and rung separation distance had a significant effect on predicted peak lower joint moments. Excessive muscle contractions were observed during ladder ascent than the descent for all four lower limb flexor and extensor muscles. The results concluded that climbing the ladder using side rails as support was more strenuous than climbing the ladder with rungs as support.
