Exploring the Relationships Between Psychosocial Factors, Biomechanical Workstyle, Muscle Tension, and Musculoskeletal Discomfort Reporting

Abstract

Psychosocial factors are becoming increasingly more prominent in studies of musculoskeletal injury. This research initiative explored various aspects associated with inclusion of trait and state psychosocial factors in laboratory-based biomechanical investigations. The project was comprised of three separate phases. The first phase involved administration of a variety of self-report surveys in written form to 83 subjects. The purpose of this effort was to explore the relationships and overlaps between various psychosocial constructs and musculoskeletal discomfort. The results were used to design the research approach and specific methods for the second and third phase laboratory experiments.

Prior to the conduct of the laboratory studies, 102 participants were pre-tested on a selected subset of written surveys. Scores on one specific survey, the Jenkins Activity Survey, were used to categorize participants as personality Type A or B. An equal number of Type A (n=12) and B (n=12) individuals completed the second experiment in which they performed an assembly task while their performance and wrist motion parameters were recorded. The task was performed under two conditions of psychosocially-imposed time stress (no-stress and stress), both imposed via verbal script. From the pre-tested pool of subjects, a separate group of Type A (N=12) and Type B (N=13) participants performed the third experiment. During this experiment, participants performed a pipetting task and a computer entry task while performance and muscle activity were measured. The pipetting task was performed under two conditions of psychosocially-imposed time stress. The computer entry task was performed under two conditions of psychosocially-imposed frustration stress. The conditions were counterbalanced across subjects in both experiments. Discomfort and anxiety reporting behaviors were evaluated in both experiments.

Personality type impacted performance during assembly but not during pipetting or computer entry. Type A assembly performance times were 12 – 14% faster than Type B's. However, personality type did not impact wrist motion kinematics. The effects of personality type on muscle tension, discomfort, and anxiety were often moderated by gender.

Psychosocially-imposed time stress impacted performance. During assembly, performance times were 11 ? 18% faster during the stress condition. During pipetting, performance time was 23% faster during the time stress condition but only when this condition followed the no-stress condition. Time stress produced 8 ? 26% increases in wrist motion velocities and accelerations during assembly. Time stress during pipetting increased muscle tension by 9 ? 23% in six of the muscles sampled. However, the dominant flexor and extensor activities only increased (by 25 to 29%) for females. In general, time stress did not impact discomfort reports, but it did increase anxiety by 8% for the assembly task.

Psychosocially-imposed frustration stress impacted computer task performance but only when the stress condition preceded the no-stress condition. For this case, performance time was 13% slower during the stress condition. Frustration stress did not impact muscle tension or discomfort reports, although it did increase reported anxiety by 6%.

The results of this study demonstrate that the biomechanical response of individuals is a complex phenomenon, encompassing interactions of individual characteristics, task characteristics, and psychosocial stress (e.g., time stress, frustration stress). Specific findings and potential implications of these findings were presented in this study. It is hoped that this effort will provide additional insight into (1) the potential biobehavioral pathways between psychosocial factors and musculoskeletal illness and (2) the methodological strategies for exploring these relationships.