To assess the effect of a vertical height adjustment of the chair and visual display unit (VDU) on work-related upper quadrant musculoskeletal pain (WRUQMP) and sitting comfort in office workers. The upper quadrant refers to the occiput, cervical and upper thoracic spine, including the clavicles and scapulae.
A single subject (
Both the mean and variance in pain intensity decreased after the workstation intervention. A deterioration in sitting comfort was noted.
The vertical height adjustment of the chair and visual display unit may have contributed to a decrease in work-related upper quadrant musculoskeletal pain in this subject. This safe, economical workstation intervention may be a practical management option for the computer user suffering from work-related upper quadrant musculoskeletal pain. Further research into the measurement of comfort whilst sitting at a computer workstation is recommended.
Prolonged computer use has become customary in present-day office work environments (Wahlstrom et al.
Of concern is that prevalence rates have not decreased over the past three decades, despite efforts to address this problem in the workplace. These workplace interventions are further complicated as a result of the multidimensional nature of the problem, with non–modifiable and modifiable risk factors applicable (Johnston et al.
Numerous studies have been undertaken to identify which factors inherent in the workstation layout are most associated with WRUQMP (Andersen et al.
However, the causal relationship of the computer workstation posture and MSD has been questioned (Andersen et al.
Clinical advice, workplace policies as well as government legislative policies need to be based on trustworthy scientific guidance (Waersted et al.
A simple vertical adjustment of only the chair and VDU height, without confounding advice or other treatment, has not been identified in the literature reviewed to date. This practical intervention would be economical and easy to implement, facilitating self-management for the office worker suffering from WRUQMP. Training time and resources add to the expense of an intervention and compliance with postural and ergonomic advice requires active participation from the computer user, who is often distracted by the workload. Therefore, an intervention which does not require any participation from the worker beyond an initial basic chair and/or VDU height adjustment is appealing.
This study was carried out to ascertain whether adjusting only the vertical height of the chair and VDU in relation to the computer user, would affect WRUQMP and sitting comfort. The hypothesis is that WRUQMP and sitting comfort would be reduced following this ergonomic intervention. The basis for this intervention is that a change in the worker-workstation interface alters the postural demand placed on the worker, and subsequently the demand on the musculoskeletal system.
A single subject experimental series type ABC, with 4 weeks per phase, was conducted. It was hypothesised that an adjustment of the chair and VDU height would reduce the subject’s WRUQMP and improve sitting comfort.
Subjects were eligible if they were office workers who used a computer for at least 5 hours per day and experienced neck or upper back symptoms associated with computer use that had been persistent or recurrent over the past 3 months. Additionally, the workstation of eligible participants had a seat and/or VDU height that was not within 10% of the seat and VDU height recommended in the literature (Hochanadel
Furthermore, potential participants were excluded if they were undergoing treatment for neck or upper back pain as this may modify their pain or comfort. Additionally, respondents who had a BMI score of greater than 30, were pregnant or smokers, or used bifocal glasses were excluded as these factors influence body anthropometry and/or musculoskeletal discomfort (Borg-Stein, Dugan & Gruber
Approval for the study was obtained from the Committee of Human Research at the University of Stellenbosch. The participant signed informed consent.
The study population – office workers in the administration department of Constantiaberg Mediclinic – was selected because of its proximity to the researcher’s own workplace. A letter was sent to the human resources department at Constantiaberg Mediclinic requesting permission to conduct the study. Permission was granted on 04 September 2013. All the office workers in the administration department who were at work that week completed a screening questionnaire, which included the inclusion and exclusion criteria for the study, in order to identify eligible subjects.
During phase A, the baseline phase, no change was made to the workstation. Phase B was the intervention phase and the workstation (chair and VDU height) was then adjusted as shown in
Recommended workstation measurements.
Measurement | Description of measurement |
---|---|
Elbow height | desk height to floor + 25 mm |
Elbow to seat distance | olecranon (with the subjects’ upper arm relaxed at their side, and the elbow flexed to 90’) to the seat |
Eye to seat distance | corner of the subject’s eye to the seat |
Intervention seat height | ‘elbow height’ – ‘elbow to seat’ distance |
Intervention visual display unit height | ‘seat height’ + ‘eye to seat’ distance |
Foot rest | The participant already had an adequate footrest which she was encouraged to use once her chair height was altered to allow her feet to rest on a firm surface |
No further ergonomic intervention or education was offered and the subject continued with her usual work for 4 weeks. At the start of phase C, the subject was informed that she was now free to change her workstation parameters, should she choose to do so.
The primary outcome was neck and upper back pain intensity and the secondary outcome was comfort level whilst sitting at work. Each outcome was measured twice a week, at the end of the workday on a Tuesday and Thursday, with a Visual Analogue Pain Scale (VAPS) and Visual Analogue Discomfort Scale (VADS), as shown in
Visual Analogue Pain Scale and Visual Analogue Discomfort Scale. VAPS, Visual Analogue Pain Scale; VADS, Visual Analogue Discomfort Scale.
Measurement time frames.
Study phase | Measurements per week | Measurements per phase |
---|---|---|
A | 2 VAPS | 8 |
2 VADS | 8 | |
B | 2 VAPS | 8 |
2 VADS | 8 | |
C | 2 VAPS | 8 |
2 VADS | 8 |
The VAS is a self-report instrument consisting of a 100 mm horizontal line, which the subject was asked to complete by making a mark on the relevant line to indicate her pain intensity and comfort during the previous 2 working days.
In comparison with discrete scales, measurement by a VAS is more exact, and the scale needs less explanation for the research participants (Reips & Funke
Known confounding factors were monitored as follows at various stages of the study.
The eligible subject was interviewed and examined by the researcher using a physiotherapy orthopaedic assessment (Petty
The 5 item Keele Generic Tool was included at the time of entry and exit from the study as psychosocial factors significantly affect pain intensity, and a change in psychosocial factors within the study period may therefore have introduced a confounding factor into the study. This is the psychosocial subscale of the STarT Back Tool, modified to screen and identify distress in conditions other than lower back pain. The Keele 5 item STarT generic screening tool was developed by Hill et al. (
At the end of phase C the subject completed an Exit Questionnaire to assess any change in these known confounding factors, as mentioned above at time of entry to the study. This would allow the researcher to consider these factors when interpreting the data.
The subject indicated if she had taken any medication for her neck or upper back pain over the previous 2 working days, each time she completed the VAPS and VADS. This was necessary to establish whether the use of analgesia had affected the pain and comfort level reported.
The subject completed a questionnaire at the end of phases A and B, in which she reported the following: if she had received any treatment for her neck or upper back, altered the workstation herself or if there were any other factors over the past 4 weeks which may have influenced her work-related symptoms.
At the end of phase C, the Exit Questionnaire included these phase end questions.
A brief exit interview was carried out to assess the subject’s overall experience of the study, and specifically her understanding of the VADS. This exit interview was carried out in an attempt to understand the discrepancy in the subject’s verbal comments to the researcher, and her reporting on the VAPS and VADS.
All data were captured on a Microsoft Excel 2010 spread sheet and descriptive statistics were used to describe the data set. As a measure of central tendency the mean was calculated and the range was calculated as a measure of variability for each phase, for the outcomes of pain and comfort. Measurements for A6 were not possible as the subject was absent that Thursday. The 2SD band method could not be used for the outcome of pain as the variance resulted in a negative -2SD value, which is not plausible for a VAPS as its lowest value is 0. The effect sizes for pain and comfort were calculated. Line graphs were drawn using Microsoft Excel 2010 to depict the trend for the outcome measures of pain and comfort.
Fifteen office workers completed the screening questionnaire, with
Flowchart of the recruitment process. WRUQMP, work-related upper quadrant musculoskeletal pain.
Subject interview and physical examination. WRUQMP, work-related upper quadrant musculoskeletal pain.
Subject workstation measurements.
Workstation variable | Chair | VDU |
---|---|---|
Usual height | 470 mm | 1360 mm |
Adjusted height | 515 mm | 1235 mm |
Mismatch | 45 mm = 9.6% (chair too low) | 125 mm = 9.2% (VDU too high) |
VDU, visual display unit.
The photographs in
Photographs of the subject’s workstation: (a) Before workstation adjustment; (b) after workstation adjustment.
The subject chose not to adjust her workstation during phase C, preferring to keep it at the phase B intervention adjustment heights.
Visual Analogue Pain Scale measurements with the mean for each phase. VAPS, Visual Analogue Pain Scale.
Visual Analogue Discomfort Scale measurements with the mean for each phase. VADS, Visual Analogue Discomfort Scale.
Means and ranges per phase for the outcomes of pain and comfort.
Outcome measure | Mean and range | Phase A | Phase B | Phase C |
---|---|---|---|---|
Pain Intensity | Mean (Min-Max) | 19 (0–37) | 11 (6–18) | 7 (3–15) |
Range | 37 | 12 | 12 | |
Discomfort | Mean (Min-Max) | 33 (15–53) | 73 (35–88) | 76 (60–85) |
Range | 38 | 53 | 25 |
Assessment of known confounders (end of phase).
Confounding variable | Phase 1 | Phase 2 | Phase 3 |
---|---|---|---|
Absent | Yes, 1 day | Yes, 1 day | No |
Other treatment received | No | No | No |
Own workstation adjustments | No | No | No |
Open question: Anything else relevant | No | No | No |
Pain medication used for neck or upper back | No | No | No |
Assessment of known confounders (end of phase C and relating to the previous 3 months).
Confounding variable | Subject’s response |
---|---|
Change in the nature of the work | No |
Change in physical work environment | No |
Change in exercise frequency | No |
Change in family and social life | Grandfather died day after measurement C4 |
Accidents or injuries | No |
Changes in general health | No |
Change in mattress or pillow | No |
Change in glasses prescription | No |
STarT Generic Screening Tool | Study entry: 2/5 (low); Study exit: 0/5 (low) |
WRUQMP is a common problem in office workers who use computers (Cagnie et al.
In our study, the trend for WRUQMP intensity decreased after the intervention was introduced (
The variability of pain decreased during the intervention and last phases. The reduced variability from phase A indicated a positive effect of the intervention, as more stability in symptoms was noted during the latter two phases. As the pain did not increase during the period of increased workload at month end, it affirms the improvement in her symptoms. The ergonomic intervention may thus have had a buffering effect on the pain intensity during periods of increased workload. Our findings pertaining to pain intensity and variability of pain are consistent with ergonomic workstation intervention studies which have reported a decrease in WRUQMP (Esmaeilzadeh et al.
Esmaeilzadeh et al. (
Conversely to our findings, Gerr et al. (
The subject in our study experienced low intensity pain, albeit frequent. This is typical of WRUQMP associated with computer use (Paksaichol et al.
This neck position has previously been significantly associated with neck MSD in computer users (Kaliniene et al.
Although a reduction in pain intensity was noted in our study, some WRUQMP remained. This is consistent with the findings by Hoyle et al. (
The secondary outcome of this study, to ascertain the effect of a chair and VDU height adjustment on comfort level whilst sitting at work, shows that the subject became more uncomfortable after the intervention phase (
Comfort has been defined as a ‘pleasant state or relaxed feeling of a human in reaction to its environment’ (Vink & Hallbeck
WRUQMP in computer users is a multidimensional problem and various risk factors may interact to increase or buffer symptoms (Johnston et al.
The subject was not blinded to the intervention and, therefore, the placebo effect may result in bias if she is under the impression that superior workstation ergonomics have been implemented (Mekhora et al.
This was a single subject study of a single intervention, and the result may not be generalised to other population groups and ergonomic interventions. Similar studies with greater numbers of subjects, or the combination of multiple single subject studies similar to the present study, would enhance the validity of the findings, therefore increasing the confidence with which clinicians may recommend this intervention. Furthermore, a desktop computer was used and the results of this study cannot be generalised to laptop, tablet or multiple screen workstation scenarios.
A strength of the studies by Esmaeilzadeh et al. (
Returning the subject’s workstation to baseline settings after phase B for a wash out period would have increased the validity of the findings. However, as this subject reported less pain after the intervention phase and chose to keep her workstation at the adjusted height, this may have been regarded as unethical. Information regarding the use of pain medication was only gained in relation to neck and upper back pain which may have introduced bias as pain medication for other areas would also have affected the WRUQMP.
The aim of this study was to ascertain whether a chair and VDU height adjustment would reduce WRUQMP in office workers who are computer users. The findings of this single subject study suggested that the vertical height adjustment of the chair and VDU may have contributed to a decrease in WRUQMP in this subject. This safe, economical workstation intervention may be a practical management option for the computer user suffering from WRUQMP. However, the reduction in reported pain levels was too small to be considered clinically significant, and a deterioration in sitting comfort was noted. Further research with larger population studies and longer follow–up time frames is now required to affirm these findings in a representative sample.
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
N.v.V. (Nicole van Vledder Physiotherapy) conceptualised the study, collected the data and drafted the article. Q.L. (University of Stellenbosch) conceptualised the study, led the data analysis and drafted the article.