Visual and psychological stress during computer work in healthy, young females-physiological responses

Abstract

Purpose: Among computer workers, visual complaints, and neck pain are highly prevalent. This study explores how occupational simulated stressors during computer work, like glare and psychosocial stress, affect physiological responses in young females with normal vision.

Methods: The study was a within-subject laboratory experiment with a counterbalanced, repeated design. Forty-three females performed four 10-min computer-work sessions with different stress exposures: (1) minimal stress; (2) visual stress (direct glare); (3) psychological stress; and (4) combined visual and psychological stress. Muscle activity and muscle blood flow in trapezius, muscle blood flow in orbicularis oculi, heart rate, blood pressure, blink rate and postural angles were continuously recorded. Immediately after each computer-work session, fixation disparity was measured and a questionnaire regarding perceived workstation lighting and stress was completed.

Results: Exposure to direct glare resulted in increased trapezius muscle blood flow, increased blink rate, and forward bending of the head. Psychological stress induced a transient increase in trapezius muscle activity and a more forward-bent posture. Bending forward towards the computer screen was correlated with higher productivity (reading speed), indicating a concentration or stress response. Forward bent posture was also associated with changes in fixation disparity. Furthermore, during computer work per se, trapezius muscle activity and blood flow, orbicularis oculi muscle blood flow, and heart rate were increased compared to rest.

Conclusions: Exposure to glare and psychological stress during computer work were shown to influence the trapezius muscle, posture, and blink rate in young, healthy females with normal binocular vision, but in different ways. Accordingly, both visual and psychological factors must be taken into account when optimizing computer workstations to reduce physiological responses that may cause excessive eyestrain and musculoskeletal load.

Keywords: Computer work; Glare; Posture; Psychological stress; Trapezius; Vision.

Fig. 1

Flowchart of the first test condition. Muscle activity, muscle blood flow, heart rate, blink rate (in PS and VPS) and postural angles were recorded continuously during rest, computer work, and recovery. Blood pressure was registered twice during the computer task (at 4 and 9 min). Fixation disparity was measured during the preparation period (baseline) and immediately after the 10-min computer-work session. Directly after the fixation disparity measurement, the participants completed the questionnaire regarding perceived lighting and stress. All four conditions included the same parts as shown in the figure (except preparation), and PPG rest recording before the first condition was used as the baseline for PPG results in all conditions

Fig. 2

Scores (mm VAS) for a how participants perceived the workstation lighting, and b the degree of stress perceived by participants during the four computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS psychological and visual stress. Higher scores indicate a a higher degree of perceived unpleasantness of the lighting, and b a higher degree of perceived stress. Results are given as mean ± SEM, n = 43

Fig. 3

Muscle blood flow in a trapezius (n = 32) and b orbicularis oculi (n = 23) during the four computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS psychological and visual stress. Results are given as percentage increase in muscle blood flow relative to the initial resting value (baseline). Rest = rest recording before computer work; Recovery = rest recording after a 14-min break (see Fig. 1). All results are given as mean ± SEM

Fig. 4

Muscle activity in trapezius: a static and b median load, during the four computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS psychological and visual stress. Rest = rest recording before computer work; Recovery = rest recording after a 14-min break (see Fig. 1). Results are given as mean ± SEM, n = 43

Fig. 5

Heart rate during the four computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS psychological and visual stress. Rest = rest recording before computer work; Recovery = rest recording after a 14-min break (see Fig. 1). Results are given as mean ± SEM, n = 35

Fig. 6

Postural angles for a back flexion/extension (leaning forward/backward, n = 35), b head flexion/extension (n = 38), c back lateral flexion (side bending, n = 31), and d head lateral flexion (n = 38) during the four computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS psychological and visual stress. Postural angles are given as degrees relative to a reference sitting position marked in the graphs with a dotted line, representing zero degrees (see “Methods”). Positive/negative values refer to forward/backward movements for flexion/extension and right/left movements for lateral flexion. Results are given as mean ± SEM

Fig. 7

Blink rate in the two conditions with psychological stress exposure: a mean blink rate during the two computer-work sessions, and b mean blink rate at start of the work session (blinks per minute during 0–1 min) and at the rest of the work session (blinks per minute during the computer-work session, excluding the first minute). PS Psychological stress, VPS psychological and visual stress. Results are given as mean ± SEM, n = 18

Fig. 8

Mean FDchange for each of the computer-work conditions. LS Low stress, VS visual stress, PS psychological stress, VPS visual and psychological stress. Negative/positive values on y-axis represent a change in fixation disparity from baseline towards an exo-/eso-disparity. Dotted line represents the mean baseline value (zero). The results are given as mean ± SEM, n = 20

Fig. 9

Significant correlations between back angle (leaning forward/backward = positive/negative values) and FDchange (change towards eso/exo-disparity = positive/negative values), productivity (reading speed, words/10 min), and orbicularis oculi muscle blood flow (in table). The correlations are given as Pearson’s correlation coefficients. The correlations plots show the associations between back angle and a FDchange in VS, PS and VPS, and b reading speed in LS, VS and PS. LS Low stress, VS visual stress, PS psychological stress, VPS visual and psychological stress. */**Statistically significant correlation at p < .05 and p < .01, respectively. (*) Close to, but not statistically significant correlation (p ≤ .060)