Huey-Wen Liang, Yaw-Huei Hwang, Lian-Yu Lin, Ta-Chen Su

1. Impact of music listening on self-reported symptoms and heart rate variability during continuous typing Huey-Wen Liang, Yaw-Huei Hwang, Lian-Yu Lin, Ta-Chen Su INTRODUCTION Table 2. The overall typing performance and pre- and post-test fatigue of two groups. 1. VDT tasks combine the features of mental demanding and repetitive. They may result in psychological stress, but the change and determinants of psychophysiological parameters during continuous typing is not well studies. 2. Listening to music while typing or engaging to VDT tasks is a common habit for many VDT users. However, if there is a positive, negative or no effect of such a habit on typing activity has not been studied. 3. We hypothesize that the psychological stress during typing can be reflected by the change of heart rate variability and music listening can modify the above change. 4. Our goal is to observe the temporal change of heart rate and heart rate variability and examine the effect of music listening on the typing performance, subjective symptoms and heart rate variability during continuous typing. Figure 1. Changes of heart rate, SDNN, high frequency component and LF/HF ratio during continuous typing. SUBJECTS AND METHODS 1. Study design: randomized, cross-sectional study 2. 43 Subjects (Table 1) -- at least 18 years; -- typing English at a net speed of at least 35 words per minute (wpm); -- using a 10-digit touch method to type; -- no history or evidence of neuropathy, arthritis, joint inflammation or recent trauma of the upper limbs; 3. Workstation: -- a standard 101-key qwerty-type keyboard (HP SK-2502C, Hewlett Packard) and a 17-inch LCD monitor (AL1714, Acer); -- non-adjustable monitor table and keyboard tray (height: 68 and 63 cm above the floor); -- adjustable five-point chair (range of seat height: 42-50 cm) without armrests; -- Subjects adjust the height of the height of the seat cushion based on personal preference and published ergonomic guidelines. 4. Typing task -- Each subjects typed in English continuously for 90 minutes without breaks. 5.Outcome: -- interkeypress intervals (IKI) recorded by electronic activity monitoring software, VDTlog and typing words recorded by TypingMaster; -- ambulatory electrocardiographic monitoring starting 10 minutes before test throughout 90-minute typing and the heart rate and heart rate variability (high frequency, low frequency and standard deviation of heart rate) were computed for every 10 minutes. -- a self-administrated questionnaire to rate the overall fatigue before and after the test; 6.Statistical analysis -- Heart rate and heart rate variability (lnHF, LF/HF ratio, SDNN) were further analyzed separately by multiple marginal regression models for repeatedly measured response variables using the generalized estimating equations (GEE) method to examine the effects of music listening over time, with adjustment of baseline data and other confounders (age, gender, habit of music listening, etc.) Table 3. Result of GEE analysis with heart rate and heart rate variability as dependent variables. Table 1. The demographic data of 43 subjects grouped by listening to music or not during typing test Parameter estimates are listed with standard error in parentheses; * p<0.05; ** p<0.01; *** p<0.001. DISCUSSION AND CONCLUSION • 1. There is a trend of slowed heart rate and reduced heart rate variability (SDNN and lnHF) during a continuous typing. The reduction of HRV is only found in the first 40 minutes, while the slowing of HR was significant at the late periods of the task. These findings are suggestive of a temporarily physiological response to the psychological stress initially and subsequent fatigue or adaptation to counterbalance the above change. • 2. High accuracy rate was associated with low heart rate variability, and it was contributed to the vigilance or alertness required for correct typing. • 3. Music listening is associated with lower heart rate variability, which implies either an arousal or strain effect. The effect is dependent on the habit of music listening, however. It is therefore not appropriate to apply music in the workplaces. • 4. The generalization of the results to the workplaces or other computer tasks required further investigation. RESULTS 1. Pain and fatigue reported after 90-minute typing tasks were of all significantly higher rating than those rated before tests. 2. There was no difference between music and no-music groups in terms of average typing speed or post-test fatigue. (Table 2) 3. Heart rate slowed gradually during 90-minute typing and the slowing was significant at the late 30 minutes (Table 3). 4. SDNN had a significant reduction in the first 40 minutes for typing in both groups, and lnHF, in the first 20 minutes. 5. Music group had lower heart rate variability (lnHF and SDNN), but the effect was counterbalanced when the subjects had habit of music listening. 6. Low heart rate variability was also associated with high accuracy rate of typing.