Effect of visual display height on modelled upper and lower cervical gravitational moment, muscle capacity and relative strain

Head and neck posture is an important factor in neck pain related to computer use; however, the evidence for an optimal posture is unconvincing. This study measured the 3-D postures of 36 young adults during use of three different display heights. Cervical extensor muscle strain was estimated using modelled gravitational load moments and muscle capacities. The influence of more or less upper vs. lower cervical movement was also explored across a broad range of potential postures. Overall cervical extensor muscle capacity diminished away from a neutral posture whilst gravity moment increased with flexion. Overall cervical extensor muscle strain increased with head flexion but remained stable into head extension. Individual differences in the amount of upper and lower cervical movement had an important effect on strain, particularly for some muscles. Computer display height guidelines are an important component of ergonomics practice, yet the relative strain on neck extensor muscles as a function of display height has not been examined. The current findings provide more detailed biomechanical evidence that ergonomists can incorporate with usability and other evidence to determine appropriate display height recommendations.

[1]  L. Straker,et al.  The impact of computer display height and desk design on muscle activity during information technology work by young adults. , 2008, Journal of Electromyography & Kinesiology.

[2]  Queensland..  Household use of information technology , 2006 .

[3]  C L Koerhuis,et al.  'Coupled motions' in cervical spine rotation can be misleading. Comment on V. Feipel, B. Rondelet, J.-P. Le Pallec and M. Rooze. Normal global motion of the cervical spine: an electrogoniometric study. Clin. Biomechanics 1999; 14: 462-470. , 2001, Clinical biomechanics.

[4]  S J Starr,et al.  Relating posture to discomfort in VDT use. , 1985, Journal of occupational medicine. : official publication of the Industrial Medical Association.

[5]  Fredric Gerr,et al.  A prospective study of computer users: II. Postural risk factors for musculoskeletal symptoms and disorders. , 2002, American journal of industrial medicine.

[6]  S. Mercer,et al.  Biomechanics of the cervical spine. I: Normal kinematics. , 2000, Clinical biomechanics.

[7]  Jack M. Winters,et al.  Multiple Muscle Systems , 1990, Springer New York.

[8]  Dennis R. Ankrum,et al.  Head and Neck Posture at Computer Workstations - What's Neutral? , 2000 .

[9]  E Grandjean,et al.  VDT Workstation Design: Preferred Settings and Their Effects , 1983, Human factors.

[10]  H Kylian,et al.  Preferred position of visual displays relative to the eyes: a field study of visual strain and individual differences. , 1998, Ergonomics.

[11]  C J Snijders,et al.  A biomechanical model for the analysis of the cervical spine in static postures. , 1991, Journal of biomechanics.

[12]  Francis L. Merat,et al.  Introduction to robotics: Mechanics and control , 1987, IEEE J. Robotics Autom..

[13]  F. Richmond,et al.  Morphometry of Human Neck Muscles , 1998, Spine.

[14]  L Straker,et al.  The impact of computer display height and desk design on 3D posture during information technology work by young adults. , 2008, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[15]  Shrawan Kumar,et al.  Quantification of isometric cervical strength at different ranges of flexion and extension. , 2005, Clinical biomechanics.

[16]  Hyeonki Choi,et al.  Quantitative assessment of co-contraction in cervical musculature. , 2003, Medical engineering & physics.

[17]  R. Kadefors,et al.  Clinical signs and physical function in neck and upper extremities among elderly female computer users: the NEW study , 2004, European Journal of Applied Physiology.

[18]  Burt Holland,et al.  Determining the relationship between cervical lordosis and neck complaints. , 2005, Journal of manipulative and physiological therapeutics.

[19]  L Finsen,et al.  Biomechanical aspects of occupational neck postures during dental work , 1999 .

[20]  D. Medina,et al.  Normative database of isometric cervical strength in a healthy population. , 2002, Medicine and science in sports and exercise.

[21]  P. McClure,et al.  The relationship between head and neck posture and VDT screen height in keyboard operators. , 1998, Physical therapy.

[22]  E Grandjean,et al.  Postural and visual loads at VDT workplaces. I. Constrained postures. , 1981, Ergonomics.

[23]  Carolyn M. Sommerich,et al.  Use of surface electromyography to estimate neck muscle activity. , 2000, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[24]  J J Meyer,et al.  Recruitment patterns in the cervical paraspinal muscles during cervical forward flexion: evidence of cervical flexion-relaxation. , 1993, Electromyography and clinical neurophysiology.

[25]  Steven Hipple,et al.  Computer and Internet Use at Work in 2001. , 2003 .

[26]  S. T. Pheasant,et al.  Bodyspace : anthropometry, ergonomics and design , 1986 .

[27]  F. Zajac.  Muscle and tendon: properties, models, scaling, and application to biomechanics and motor control. , 1989, Critical reviews in biomedical engineering.

[28]  J P Psihogios,et al.  A field evaluation of monitor placement effects in VDT users. , 2001, Applied ergonomics.

[29]  S L Delp,et al.  A graphics-based software system to develop and analyze models of musculoskeletal structures. , 1995, Computers in biology and medicine.

[30]  V Feipel,et al.  Normal global motion of the cervical spine: an electrogoniometric study. , 1999, Clinical biomechanics.

[31]  Jennie P. Psihogios,et al.  The effects of video display terminal height on the operator: a comparison of the 15° and 40° recommendations , 1998 .

[32]  J. Winters,et al.  Neck Muscle Activity and 3-D Head Kinematics During Quasi-Static and Dynamic Tracking Movements , 1990 .

[33]  M. P. J. M. Van Riel,et al.  Improving the sitting posture of CAD/CAM workers by increasing VDU monitor working height , 1992 .

[34]  D. Kleinbaum,et al.  A prospective study of computer users: I. Study design and incidence of musculoskeletal symptoms and disorders. , 2002, American journal of industrial medicine.

[35]  Kevin Netto,et al.  Examination of EMG normalisation methods for the study of the posterior and posterolateral neck muscles in healthy controls. , 2007, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[36]  C. Blehm,et al.  Computer vision syndrome: a review. , 2005, Survey of ophthalmology.

[37]  K. Harms-Ringdahl.  On assessment of shoulder exercise and load-elicited pain in the cervical spine. Biomechanical analysis of load--EMG--methodological studies of pain provoked by extreme position. , 1986, Scandinavian journal of rehabilitation medicine. Supplement.

[38]  C J Snijders,et al.  The effect on sitting posture of a desk with a ten-degree inclination using an adjustable chair and table. , 1991, Applied ergonomics.

[39]  M Thoresen,et al.  Musculoskeletal, visual and psychosocial stress in VDU operators before and after multidisciplinary ergonomic interventions. , 1998, Applied ergonomics.

[40]  K Schüldt,et al.  On neck muscle activity and load reduction in sitting postures. An electromyographic and biomechanical study with applications in ergonomics and rehabilitation. , 1988, Scandinavian journal of rehabilitation medicine. Supplement.

[41]  G. Mirka,et al.  Low-level exertions of the neck musculature: a study of research methods. , 2006, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[42]  Ben-Tzion Karsh,et al.  Theories of work-related musculoskeletal disorders: Implications for ergonomic interventions , 2006 .

[43]  R. Burgess-Limerick,et al.  The effect of imposed and self-selected computer monitor height on posture and gaze angle. , 1998, Clinical biomechanics.

[44]  P M Bongers,et al.  Are neck flexion, neck rotation, and sitting at work risk factors for neck pain? Results of a prospective cohort study , 2001, Occupational and environmental medicine.

[45]  M. Revel,et al.  Surface electrodes are not appropriate to record selective myoelectric activity of splenius capitis muscle in humans , 2004, Experimental Brain Research.

[46]  M. Jj,et al.  Recruitment patterns in the cervical paraspinal muscles during cervical forward flexion: evidence of cervical flexion-relaxation. , 1993 .

[47]  M J Griffin,et al.  Prevalence and occupational associations of neck pain in the British population. , 2001, Scandinavian journal of work, environment & health.

[48]  B S Myers,et al.  Surface friction in near-vertex head and neck impact increases risk of injury. , 1999, Journal of biomechanics.

[49]  Carolyn M. Sommerich,et al.  Effects of Computer Monitor Viewing Angle and Related Factors on Strain, Performance, and Preference Outcomes , 2001, Hum. Factors.

[50]  Leon M Straker,et al.  A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work--1: neck and shoulder muscle recruitment patterns. , 2005, Manual therapy.

[51]  Keith T Palmer,et al.  Soft-tissue rheumatic disorders of the neck and upper limb: prevalence and risk factors. , 2003, Seminars in arthritis and rheumatism.

[52]  G. Németh,et al.  Load moments and myoelectric activity when the cervical spine is held in full flexion and extension. , 1986, Ergonomics.

[53]  S. Delp,et al.  Influence of Muscle Morphometry and Moment Arms on the Moment‐Generating Capacity of Human Neck Muscles , 1998, Spine.

[54]  J P Psihogios,et al.  The effects of video display terminal height on the operator: a comparison of the 15 degree and 40 degree recommendations. , 1998, Applied ergonomics.

[55]  Karen Søgaard,et al.  Work related neck-shoulder pain: a review on magnitude, risk factors, biochemical characteristics, clinical picture and preventive interventions. , 2007, Best practice & research. Clinical rheumatology.

[56]  C. Buxó,et al.  Factors leading to the computer vision syndrome: an issue at the contemporary workplace. , 2004, Boletin de la Asociacion Medica de Puerto Rico.

[57]  Karen Søgaard.  Occupational biomechanics of the upper extremities; a search for the cause and prevention of musculoskeletal disorders , 2007 .

[58]  A. Papageorgiou,et al.  Predicting Persistent Neck Pain: A 1-Year Follow-up of a Population Cohort , 2004, Spine.

[59]  L. Straker,et al.  An evaluation of visual display unit placement by electromyography, posture, discomfort and preference , 2000 .

[60]  M. P. J. M. Van Riel,et al.  The effect on sitting posture of a desk with a 10° inclination for reading and writing , 1991 .

[61]  W. T. Dempster,et al.  SPACE REQUIREMENTS OF THE SEATED OPERATOR, GEOMETRICAL, KINEMATIC, AND MECHANICAL ASPECTS OF THE BODY WITH SPECIAL REFERENCE TO THE LIMBS , 1955 .

[62]  L. Keltikangas-Järvinen,et al.  Personality factors as predictors of compliance with and the outcome of supervised self-care program for patients with intermittent claudication. , 1987, Scandinavian journal of rehabilitation medicine.