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Title: An interactive physio-psychological model on understanding stress among individuals performing sedentary computer tasks
Authors: Wang, Yuling
Degree: Ph.D.
Issue Date: 2012
Abstract: Modern day people commonly suffer from musculoskeletal disorders associated with intensive computer use, which has many important physical and mental risk factors. The overall purpose of this thesis was to investigate the acute physiological and psychosocial responses exposed to stress-induced workloads among computer users with and without neck pain. A pilot study and a main study were conducted to explore the effects of different combinations of physical and mental workloads using different forms of computer tasks in order to produce stress-induced responses in different body systems. The pilot study examined the effects of physical and mental workload in three computer tasks on muscle activity and cardiovascular measures. Fourteen healthy, pain-free adults (7 males and 7 females, mean age = 23.72 ± 3.0 yrs) were asked to complete three tasks of 15 minutes each. The tasks were (1) copy-typing ("typing"), (2) typing at progressively faster speeds ("pacing"), and (3) mental arithmetic plus fast typing ("subtraction"). Median muscle activity (50th percentile amplitude probability distribution function) was examined in 5-minute intervals during each task and each rest period, and statistically significant differences in the time factor (within task) and time × task factors were found in the bilateral cervical erector spinae (CES) and upper trapezius (UT) muscles. In contrast, distal forearm muscle activities (extensor carpi radialis and flexor carpi ulnaris) did not show any significant differences among the three tasks. Heart rate (HR) and blood pressure (BP) showed significant differences during tasks compared to baseline, and diastolic blood pressure (DBP) was significantly higher in the subtraction task than in the pacing task. The results suggest that cervical postural muscles had higher reactivity than forearm muscles to high mental workload tasks. Cervical muscles were also more reactive to tasks with high physical demand than high mental demand. HR and BP seemed to respond similarly to high physical and mental workloads.
The aims of the main study were to investigate the responses of the objective measures in the muscular system, neurophysiological system, and cardiovascular system. The physiological markers included surface electromyography (EMG), electroencephalography (EEG), heart rate variability (HRV), HR, and BP. In addition to these physiological measurements, subjective responses were recorded in terms of rate of perceived exertion (RPE), anxiety, and discomfort. The behavioral performance measures included the number of total trials and the accuracy of completed Stroop trials. In the main study, 46 adult university students, with 22 males and 24 females (mean age = 23.7 ± 3.7 years). All participants were categorized into the Pain-Free Group (n = 23) or the Neck Pain Group (n = 23). Each participant was required to perform five tasks: Task 1, a self-paced copy-typing task; Task 2, a fast copy-typing task; Task 3, a fast copy-typing CWT; Task 4, a verbal CWT; and Task 5, a prolonged CWT using a standardized computer workstation. The overall results indicated that the combined high-physical and high-mental workloads elicited consistent trends of greater increases in activity of various physiological measures compared to high-physical or high-mental workloads alone. Brain activity seemed to be more sensitive in response to all three types of workload variation, whereas muscular activity seemed to be more responsive to physical workload or physical-plus-mental workload. HRV showed more variable response patterns, especially in the Neck Pain Group compared to Pain-Free Group. The effects of sustained high-physical and high-mental demands (Task 5) produced similar but more exaggerated responses in various systems. While these physiological changes within the body systems occurred largely in similar directions of change in both groups of participants, the Neck Pain Group experienced significant increases in feelings of discomfort and anxiety, whereas the Pain-Free Group did not. The increased symptom scores in the symptomatic group were also accompanied by poorer behavioral performance, with fewer total completed trials, fewer correct trials, and longer response time in the Stroop task. In conclusion, the study confirms the important association between physiological and psychosocial responses in people with and without neck pain. The results also support the phenomenon that individuals with chronic pain have pain-related cognitive impairment and maladaptive physiological responses. However, this study cannot confirm any cause-and-effect relationship between these mechanisms due to its cross-sectional study design. Extensive research needs to be continued to further understand the inter-relationship between physical and mental stress factors in the human body.
Subjects: Neck pain.
Pain -- Psychological aspects.
Job stress.
Occupational diseases.
Computers -- Health aspects.
Hong Kong Polytechnic University -- Dissertations
Pages: xxiii, 227, 33, 19 leaves : ill. ; 30 cm.
Appears in Collections:Thesis

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