Date of Award


Publication Type

Master Thesis

Degree Name




First Advisor

Potvin, James,


Health Sciences, Occupational Health and Safety.




Sudden loading of the trunk, especially when it is unexpected, leads to higher muscle forces. Muscle fatigue, on the other hand, decreases the force producing capacity of muscles. The current experiment provides insight into the control of spine mechanics during trunk muscle fatigue in a situation of sudden loading that affects spinal stability. Fifteen females received a sudden load in the hands, at a time that could be anticipated and at a time that could not. Participants received these loading trials (a) while rested, (b) with back muscle fatigue, and (c) with a combination of back and abdominal muscle fatigue. Measures were taken from the EMG activity from four trunk muscles (LES, TES, EO and IO), and from the Trunk Angle and CoP data. A 3 x 2 Repeated Measures ANOVA was performed to determine the effects of trunk muscle fatigue and load timing on the preparations made prior to the load impact, and on the responses that followed. Results showed there were no preparations made prior to the perturbation when it could be anticipated. The Peak Responses following the perturbation were greater in the unexpected versus the expected condition. Therefore, preparations must have taken place prior to the anticipated perturbations, perhaps in other segments of the body. An increase in the trunk muscle fatigue led to an increase in the Baseline activity of the trunk muscles, but had no effect on the Peak Responses of the trunk muscles. Hence, the increased activation with fatigue was somewhat successful in decreasing the effect of the perturbation. Also, there was increased activation of both (opposing) muscle groups when only one muscle group was fatigued. This is evidence of cocontraction and supports the concept of spinal stability. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .G76. Source: Masters Abstracts International, Volume: 42-03, page: 0922. Adviser: James Potvin. Thesis (M.H.K.)--University of Windsor (Canada), 2003.