Women in Benin commonly participate in physically demanding activities that involve the carriage of heavy loads on the head and back. These strenuous tasks combined with pregnancy can result in back pain that may persist after delivery in some cases. The objective of this study was to examine how the trunk postures of pregnant women in Benin were affected by their occupational activities. This study also examined trunk postures, as well as postures of the head relative to the trunk, in the specific task of carrying loads on the head. Finally, the instrument used in this study to measure trunk postures, the Virtual CorsetTM (VC) (Microstrain, Williston, VT, USA), was validated against a system of potentiometers. Questionnaires completed by 26 pregnant and 25 non-pregnant subjects revealed that 58% of pregnant women suffered from back pain since the start of pregnancy. An average of 328 instances of trunk flexion at angles larger than 60° were recorded during the workdays of 17 pregnant women, while 66 of those flexions events were held for more than four seconds. Furthermore, an average of 36% of the recorded workday was spent in trunk flexion at angles exceeding 20°. Trunk postural data, at C7 and S1, as well as sagittal positions of the head relative to the trunk were compared between pregnant and non-pregnant subjects and between unloaded and loaded walking conditions for the specific task of head load carriage. These comparisons showed that load on the head significantly increased upper trunk extension and lateral bending of the upper trunk towards the left during walking. Motion of the head relative to the trunk and motion of the upper trunk significantly decreased in the loaded condition and was compensated by increased motion at the sacrum level. In the validation study, the VC was moved at different speeds to observe the effects of accelerations on the angle measurements. Root mean square difference between the angles measured by the VC and the potentiometers were all below 5° and 6° for flexion-extension and lateral bending, respectively, with the exception of rapid movements where errors were slightly larger. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-07-07 16:23:53.56

Neck pain and injuries remain prevalent in many occupational categories. Risk factors include non-neutral neck postures and head loads. Most ergonomic tools do not account for the changes associated with these risk factors, or the effects that head position and load can have on the upper extremities. The purpose of this study was to investigate the effects of different neck postures and head loads on cervical discomfort and upper extremity functional integrity. Participants maintained flexed, extended, protracted, and neutral neck postures for a total of 4 minutes each. These trials were done both with and without a 3.68 kg head load. After each trial, measures of cervical discomfort, changes in hand sensation, hand and pinch grip strength, and holding forces were recorded. Cervical discomfort was found to increase in non-neutral postures and with the addition of a head load. Extension resulted in the greatest levels of discomfort, followed by flexion and protraction, with similar levels of discomfort, and neutral, which caused the least discomfort. Sternocleidomastoid activity increased in a loaded, non-neutral posture compared to an unloaded, neutral posture. These data could be implemented into current ergonomic tools to more comprehensively assess task demands and reduce the risk of injury. / Thesis / Master of Science in Kinesiology