Back Pain and Work during Pregnancy: Identification of Problems and Biomechanical Analysis
| Principal investigator(s): | Genevieve Dumas (Queen’s University) |
| Co-investigator(s): | Robert Jensen, Andre Plamondon (Laurentian University); Michael McGrath, Joan Trammer (Kingston General Hospital); Caroline Weber (Queen’s University) |
| Institution: | Queen’s University |
For more information on this study, please contact Genevieve Dumas at email: dumas@me.queensu.ca
Results
- Identifying problematic tasks - Bending, lifting, and carrying were found to be the most problematic tasks for pregnant women at work and at home. At work, the most problematic task was sitting followed by bending, lifting, and carrying. Getting tired, uncomfortable posture, and excessive time in same posture were the main factors related to problems performing the work tasks. The low back had the highest rating of discomfort in the body, which may relate to the amount of low back pain reported.
- The biomechanical model - The results showed that the model could be reliably used in biomechanical analysis of spinal loads for pregnant women and other subjects during various complex tasks.
- Biomechanical analysis of an assigned task - The results showed that body changes during pregnancy have an effect on loads at the lumbo-sacral level; in particular, the loads increase with advancing pregnancy due to the gain of upper body mass. Some women experienced loads at the lumbosacral level that were higher at postpartum than during pregnancy when they performed the same tasks, an effect that cannot be explained by changes of upper body mass. This may be related to the use of lifting strategies that are different during pregnancy than at postpartum. A more detailed analysis is needed to examine what other factors (e.g., accelerations, posture) explain these unexpected patterns. Also, more subjects are needed to confirm the generality of these patterns.
Conclusion
For future studies, it is interesting to know how the back muscles react to increased loads at the spine and whether the muscles are the cause of discomfort or even pain in the back. It is also interesting to know what strategies are required of pregnant women to cope with increased loads and body changes.
Objectives
- to identify problematic tasks experienced by pregnant women in the work place and factors associated with these problematic tasks;
- to develop a biomechanical model and protocol that takes into account the changing body parameters of pregnant women to accurately evaluate loads on the lumbar spine during realistic occupational tasks; and
- to perform a biomechanical analysis of a few selected problematic tasks to evaluate factors associated with pregnancy (increase in body mass, posture) that increase loads on the spine.
Method
The study consists of three parts: a survey of pregnant women to identify problematic tasks, the development and validation of a biomechanical model to analyze loads on the spine during physical tasks, and a biomechanical analysis of selected tasks.
Identifying problematic tasks
Problematic tasks and influencing factors were identified through a survey of pregnant women at 20 and 34 weeks of pregnancy using three questionnaires: Initial Survey, Job Analysis Survey, and Task Description Form. Comprehensive information relevant to problematic tasks performed by pregnant women was collected and analyzed statistically. This information includes demographics from the Initial Survey, problematic tasks from the Job Analysis Survey, and details of involvement in a task (such as posture, duration, frequency, and load) from the Task Description Form. Data on back pain and discomfort in the body were also collected and analyzed.
Seventy-three subjects were surveyed in this study, of which 36 subjects completed the forms for both 20 and 34 weeks, 18 filled out only the 20 week forms and 19 only the 34 week forms. In total, 109 Initial Survey questionnaires were completed. The subjects submitted 322 reports of problematic tasks in the work place and at home, of which 105 reports of problematic work tasks were described using the Task Description Form.
The biomechanical model
An individualized link-segment biomechanical model was developed consisting of 12 segments for monitoring the whole body motion during an occupational task. The model uses kinematic data measured by an electromagnetic motion tracking system (MotionStar®) and anthropometric data measured by a geometric method for taking into account body changes during pregnancy. Therefore, this model is appropriate to analyze the loads on the spine of pregnant women performing complex tasks. The performance of the model was evaluated by comparing the loads at L5/S1 with the loads measured using a force plate obtained by two approaches.
Biomechanical analysis of an assigned task
A task involving lifting a file folder from a low drawer and placing it on a table was analyzed. The selection of the task was based on the considerations that it is an activity required by a wide range of occupations and that low-origin lifting tasks become increasingly difficult for pregnant women as pregnancy advances.
Two styles of lifting (freestyle lifting and squat lifting) to three orientations (0 degrees in from of the subject, 90 degrees to the right, and 90 degrees to the left) were measured. Six pregnant women and six non-pregnant women were involved in the task analysis. The pregnant subjects were tested at early and late pregnancy and postpartum. The loads at L5/S1 were analyzed.
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