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Tuesday, June 6, 2023

Comparison of Symptomatic and Asymptomatic Office Workers Performing Monotonous Keyboard Work, Part 2: Neck and Shoulder Kinematics

Brent Brookbush

Brent Brookbush


Research Review: A Comparison of Symptomatic and Asymptomatic Office Workers Performing Monotonous Keyboard Work – 2: Neck and Shoulder Kinematics

By Jacky Au, PhD

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, H/FS

Original Citation:

Szeto, G. P., Straker, L. M., & O’Sullivan, P. B. (2005) A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work—2: neck and shoulder kinematics. Manual therapy10(4), 281-291. ABSTRACT


Neck and shoulder pain has a likely prevalence of 20-30% among office workers (1). This 2005 study from Chinese and Australian researchers compared the kinematics of women with and without chronic neck/shoulder pain during a 1-hour typing task. Despite using a standardized and individually adjusted ergonomic work stations, symptomatic women exhibited forward head posture, less cervical lateral flexion and rotation to the right, greater right shoulder flexion, less right shoulder abduction and an increase in upper trapezius activity. These results suggest that neck and shoulder pain among office workers is correlated with posture and position, despite attempts to improve ergonomics.

Relevant Image:

Study Summary

Study DesignQuasi-Experimental Study
Level of Evidence IIA Evidence from at least one controlled study without randomization
Participant CharacteristicsDemographics
  • Female office workers
  • Experienced touch-typists
  • 23 symptomatic participants
  • Mean age: 35.8 ± 4.6
  • 20 asymptomatic participants
  • Mean age: 31.3 ± 7.2

Inclusion Criteria

Symptomatic Participants

  • Complaints of neck/shoulder discomfort within the previous 7-days
  • Neck/shoulder discomforts lasting more than 3-months within the previous year

Asymptomatic Participants

  • No current or past history of significant neck/shoulder discomfort

Exclusion Criteria

Past traumatic injuries or surgical interventions in neck and upper limb regions - as noted in companion paper (2)

  • Head, neck and shoulder kinematics were collected throughout a 1-hour typing task at 5, 20, 35, 50, and 60-minute time intervals
  • Each time interval included one-minute of data collection
  • Electromyography (EMG) of the upper trapezius was correlated with neck and shoulder kinematics.


  • Participants typed a children’s story that was displayed on a screen.
  • Participants were situated on an ergonomic desk that was individually adjusted according to optimal posture standards - as described in references 3 and 4.
Data Collection and Analysis

Data Collection

Kinematic data was collected via the video technology, the Vicon Bodybuilder (Oxford Metrics, UK).

Data Analysis

  • Three separate MANOVA models were run to assess the kinematics of the neck, shoulder, and thorax.
  • Dependent variables consisted of median angle and range of motion (ROM) for each of the following movements:
    • Model 1: Neck flexion/extension, neck left/right side flexion, neck rotation
    • Model 2: Thoracic flexion/extension, thoracic left/right side flexion
    • Model 3: Shoulder flexion/extension, shoulder abduction/adduction

  • Independent Variables
    • Time (5, 20, 35, 50, 60 minutes)
    • Group (Symptomatic, Asymptomatic)
    • Shoulder Laterality (Right, Left)

  • Significant effects were followed up by univariate ANOVAs to probe the separate contributions of each dependent variable to the multivariate model.
  • A posthoc moderator analysis was run separating the symptomatic group into two subgroups based on high and low discomfort levels (scores greater than or less than/equal to 12, respectively).
  • Spearman’s rho correlations were analyzed for the median angles, EMG activity, and mean discomfort scores of the neck and shoulders.
Outcome MeasuresKinematic Measurements
  • Anatomical angles were computed using the Vicon Bodybuilder, and the 10th, 50th, and 90th percentile of the amplitude probability distribution were then calculated (see 5–7). The 50th percentile was used to quantify the median angle of each movement, while the difference between the 90th and 10th percentiles were used to capture total ROM.

Self-Report Discomfort Levels

  • Participants rated task-specific discomfort in the neck and shoulder region using the Standardized Nordic Questionnaire (8).
ResultsDescriptive Summary
  • Throughout the 1-hr typing task, symptomatic participants presented with increased neck flexion range of about 2.3º relative to controls (but no differences in the median angle at which they held their heads), along with decreased right side flexion (~1.5º) and rotation (~2.4º) in the neck. Moreover, they also had greater right shoulder flexion (~1º) and less right shoulder abduction (~3º). These effects were generally correlated with increased muscle activity in the right upper trapezius, and increased discomfort.


Significant effects are shown below. For non-significant results, refer to the original paper.



  • main effect of group (F6,31 =4.04, p=0.004)


  • Flexion/extension range – main effect of group (F1,36 =4.74, p=0.036)
  • Side to side flexion median angle – main effect of group (F1,36 =5.56, p=0.024)
  • Side to side flexion range – main effect of group (F1,36 =.89, p=0.035
  • Side to side rotation median angle – main effect of group (F1,36 =9.47, p=0.004)


 No significant effects



  • Main effect of laterality: (F4,33 =8.21, p<0.001)


  • Flexion/extension median angle – main effect of laterality (F1,36 =4.30, p=0.045)
  • Flexion/extension range – main effect of laterality (F1,36 =25.99, p<0.001)
  • Abduction/Adduction range – main effect of laterality (F1,36 =7.55, p=0.009)
  • Abduction/Adduction range – interaction between laterality and time (F4,144 =4.18, p=0.003)

Post-hoc Comparisons

 No significant effects between high and low discomfort groups were found.


Median angles vs. right upper trapezius EMG activity:

  • Neck flexion: r = 0.366, p=0.024
  • Neck side flexion: r=0.336, p=0.039
  • Right shoulder abduction: r=0.348, p=0.032

Median angles vs. right neck discomfort scores:

  • Neck flexion: r=0.561, p<0.001
  • Neck side flexion: r=0.392, p=0.015
  • Neck rotation: r=-0.421, p=-.008

Median angles vs. right shoulder discomfort scores:

  • Neck side flexion: r=0.561, p<0.001
  • Neck rotation: r=-0.323, p=0.048.

Participants experiencing neck and shoulder pain, compared to asymptomatic participants intrinsically adopted mal-adaptive postural control patterns, independent of the physical environment or workstation. This was especially prominent in the high discomfort subgroup. Specifically, symptomatic individuals displayed greater neck flexion, with less right side flexion and rotation, accompanied by upper trapezius over-activity.

How this study contributes to the body of research:

Several studies have correlated a higher prevalence of neck and shoulder pain, as well as loss of range of motion (ROM), among computer/desk workers. Ergonomic solutions are commonly recommended (4,11,12), but this study suggests that dysfunction persists in symptomatic individuals despite custom ergonomics. Specifically, symptomatic participants exhibit altered neck/shoulder posture, ROM and trapezius activity, within a few minutes of a typing task. This study may suggest that in addition to ergonomic strategies, additional therapeutic interventions are recommended.

How the Findings Apply to Practice:

The findings of this study imply that symptomatic individuals will exhibit signs of impairment and complain of pain, even with individualized ergonomic desk set-up. Human movement professionals should consider assessment of impairments, for example, the deep cervical flexor endurance test, goniometric assessment of the cervical spine and shoulder range of motion, and trigger point palpation of the upper trapezius. Ergonomic workstations should continue to be recommended, but this study suggests that additional interventions, such as manual therapy and corrective exercise, may be necessary to address impairments and pain.


  1. With the prevalence of desk/computer work continuing to climb, and complaints of neck and shoulder dysfunction continuing to rise despite advances in ergonomic work stations, this study addressed a currently relevant issue (13, 14).
  2. The use of a 3D motion analysis system allowed simultaneous measurement of multiple body segments and body position rather than focus on a single impairment.
  3. Simultaneous collection of kinematic data, EMG, and self-reported discomfort allowed for an analysis of the correlation between these 3 variables.

Weakness and limitations

  1. No statistical differences were found between high and low discomfort subgroups, despite the author's emphasis on the high discomfort subgroup. Perhaps, an additional outcome measure or a larger number of participants is needed to identify differences between the high and low discomfort groups.
  2. The use of a simple touch-typing task does not fully simulate real work environments, which involve mouse use, as well as psychological factors such as stress, focus, and decision-making.
  3. It was not clear whether participants were aware of the time intervals between data collection points, which could have an affect on participant posture and reported discomfort.

How the study relates to Brookbush Institute Content

The Brookbush Institute (BI) continues to develop and refine models of Postural Dysfunction  including cervicothoracic dysfunction. This study demonstrates the persistence of altered posture correlated with neck and shoulder discomfort, despite attempts to improve ergonomics. The BI has integrated the findings of this study (forward head posture, less cervical lateral flexion and rotation to the right, greater right shoulder flexion, less right shoulder abduction and an increase in upper trapezius activity) into modeling of cervicothoracic dysfunction, as well as used these findings to refine exercise and rehabilitation recommendations. The BI will continue to pursue optimal practice, aggregating the results of all available research in pursuit of an evidence-based, integrated, systematic, outcome-driven approach.

Additional Readings:


The following videos illustrate common assessment techniques and interventions used to treat neck/shoulder pain as described in this study:

Deep Cervical Flexor Endurance Test

Deep Cervical Flexor Activation

Deep Cervical Flexor Activation and Progressions for Stabilization 2

Upper Trapezius, Levator Scapulae, Splenii and Rhomboid Vibration Release

Lower Trapezius Activation Taping


  1. Punnett L, Wegman DH (2004): Work-related musculoskeletal disorders: the epidemiologic evidence and the debate. J Electromyogr Kinesiol 14: 13–23.
  2. Szeto GPY, Straker LM, O’Sullivan PB (2005): A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work—1: Neck and shoulder muscle recruitment patterns. Man Ther 10: 270–280.
  3. Chaffin DB (1987): Occupational biomechanics—a basis for workplace design to prevent musculoskeletal injuries. Ergonomics 30: 321–329.
  4. Grandjean E, Kroemmer K (1997): Fitting the Task to the Human: A Textbook of Occupational Ergonomics. CRC Press.
  5. Jonsson B (1982): Measurement and Evaluation of Local Muscular Strain in the Shoulder During Constrained Work. J Hum Ergol (Tokyo) 11: 73–88.
  6. Nordander C, Hansson G-Å, Rylander L, Asterland P, BystrÖm JU, Ohlsson K, et al. (2000): Muscular rest and gap frequency as EMG measures of physical exposure: the impact of work tasks and individual related. Ergonomics 43: 1904–1919.
  7. Hägg GM, Åström A (1997): Load pattern and pressure pain threshold in the upper trapezius muscle and psychosocial factors in medical secretaries with and without shoulder/neck disorders. Int Arch Occup Environ Health 69: 423–432.
  8. Kuorinka I, Jonsson B, Kilbom A, Vinterberg H, Biering-Sørensen F, Andersson G, Jørgensen K (1987): Standardised Nordic questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon 18: 233–237.
  9. Fejer R, Kyvik KO, Hartvigsen J (2006): The prevalence of neck pain in the world population: a systematic critical review of the literature. Eur Spine J 15: 834–848.
  10. Cook C, Burgess-Limerick R, Chang S (2000): The prevalence of neck and upper extremity musculoskeletal symptoms in computer mouse users. Int J Ind Ergon 26: 347–356.
  11. Joseph JG, Gosavi PM, Jagtap VK (2018): Effect of Adopting Ergonomic Principles in Office Employees with Forward Head Posture. Indian J Physiother Occup Ther - Int J 12: 17.
  12. Mekhora K, Liston CB, Nanthavanij S, Cole JH (2000): The effect of ergonomic intervention on discomfort in computer users with tension neck syndrome. Int J Ind Ergon 26: 367–379.
  13. RØe C, BjØrklund RA, Knardahl S, WÆrsted M, VØllestad NK (2001): Cognitive performance and muscle activation in workers with chronic shoulder myalgia. Ergonomics 44: 1–16.
  14. Westgaard RH (2000): Work-related musculoskeletal complaints: some ergonomics challenges upon the start of a new century. Appl Ergon 31: 569–580.

© 2020 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged -