ZACKBACK® Posture Chair
for the Computer, Microscope & Microtome


"I'm not even sure it should be called a 'chair.' There are chairs, and then there is the ZACKBACK. The two have very little design details in common; the ZACKBACK actually enhances your ability to work while seated.

The thought of doing without the ZACKBACK - of going back to ordinary chairs - is horrifying. Fortunately for me, that's not going to ever happen.

I've bought a lot of chairs that claim to be ergonomically designed. The ZACKBACK makes those fallacious claims laughable. This chair is far and away the best."

-Terry Goodkind
New York Times
Bestselling Author


"After a day or so of getting used to your 'sitting system' (it's a lot more than just a chair!), a ton of chronic pain vanished from my body. It's a far bigger improvement than I thought possible in my wildest dreams.

Thanks and thanks also for the superb customer support. I wish you all the luck in the world in getting your message to more people. What you say is true: How you sit makes a huge difference in how you feel..."

-Ken McCarthy
Internet Pioneer, Speaker, and Author

Click here for more reviews of the most acclaimed chair for relieving pain and improving posture.   Microscope and Microtome users click here for your healthiest posture.


Want to Enhance Your Workday Performance?

...Then optimize your workday posture, breathing, & core stability with ZACKBACK!

Here's why ZACKBACK's Core Posture is your B.E.S.T. Posture.

Breathing: The unique lower thoracic support (figure 1) of the ZACKBACK chair immediately promotes proper diaphragmatic breathing (figure 2). Leaning against other so-called ergonomic backrests restricts diaphragmatic breathing and promotes unhealthy upper chest breathing. This results in overuse of the scalene muscles, a major cause of neck pain, referred arm pain, thoracic outlet syndrome, and fatigue (figures 3 and 4).

ZACKBACK’s lower thoracic support dramatically improves diaphragmatic breathing for 2 reasons:
(1) Mechanical support to the lower thoracic spine elevates the rib cage and prevents its downward movement. This mechanical support immediately reduces the static load on the scalene muscles.
(2) The isolated firm pressure stimulation to the lower thoracic region of the back elicits certain reflexes (called the intercostal-to-phrenic reflexes) that activate the diaphragm.

Elongation: The unique, multi-adjustable, dual back support system of the ZACKBACK chair elongates (lengthens) your spine for healthy, elegant posture. (See figure 1.) Chairs with lumbar support shorten and distort your spine! (See figure 5.) Elongation gives a feeling of weightlessness to your lower back when sitting. Lumbar support gives a feeling of compression to your lower back when sitting.

Stability: ZACKBACK’s sacral support stabilizes the pelvis in its proper neutral position and ZACKBACK’s lower thoracic support elevates and stabilizes the rib cage. (See figure 1.). As a result, a slumped sitting posture and its associated health risks are prevented. These two critical areas requiring isolated stabilization (the pelvis and the rib cage) are ignored by proponents of lumbar support and reclining backrests. In addition, breathing in the ZACKBACK chair results in a co-activation of the diaphragm and deep lower abdominals (transversus abdominis) - the key to enhancing core stability.

Tone: The distorted sitting postures in other chair designs (reclining backrests, lumbar supports) relax the lower abdominals (including the important transversus abdominis), resulting in a protruding lower abdomen. (See figure 3.) By promoting proper activation of the transversus abdominis, the ZACKBACK chair increases your lower abdominal muscle tone as you sit, resulting in a taut lower abdominal wall! (See figures 1 and 2.)

Figure 1.
ZACKBACK's dual back support system
Figure 2.
ZACKBACK Sitting involves a raised position of the diaphragm. Note in particular the greater depth and expansion of the lower rib cage.
Figure 3.
When leaning against other backrests, there is a relaxation of the abdominal muscles and a lowered position of the diaphragm. Diaphragmatic breathing will be restricted and upper chest breathing will be emphasized.
Figure 4.
Upper chest breathing results in overuse of the scalene muscles to elevate the upper two ribs against gravity.

Figure 5.
Sitting with lumbar support. Note the unhealthy backwards displacement of the upper trunk, and the overstretching of the abdominal muscles.
Lumbar support shortens, compresses, and distorts the spine.




O’Sullivan, P.B., et al.: The effect of different standing and sitting postures on trunk muscle activity in a pain-free population. Spine, 27:1238-1244, 2002.

Anderson, T. McC.: Human Kinetics and Analysing Body Movements. London, Heinemann, 1951.

Alexander, F.M.: Man’s Supreme Inheritance. New York, Dutton, 1918.

Cohen, L.A.: Role of eye and neck proprioceptive mechanisms in body orientation and motor coordination. Journal of Neurophysiology, 24:1-11, 1961.

Laville, A.: Postural stress in high-speed precision work. Ergonomics, 28:229-236, 1985.

Paris, S.V.: Cervical symptoms of forward head posture. Topics in Geriatric Rehabilitation, 5(4):11-19, 1990.

Stewart, S.F.: Physiology of the unshod and shod foot with an evolutionary history of footgear. American Journal of Surgery, 68:127-138, 1945.

Leibowitz, J.: For the victims of our culture: the Alexander technique. Dance Scope, 4:32-37, 1967.

Akerblom, B.: Standing and Sitting Posture. Stockholm, Nordiska Bokhandeln, 1948.

Andersson, G.B.J., Murphy, R.W., Ortengren, R., and Nachemson, A.L.: The influence of backrest inclination and lumbar support on lumbar lordosis. Spine, 4:52-58, 1979.

Bridger, R.S., Wilkinson, D., and Van Houweninge, T.: Hip joint mobility and spinal angles in standing and in different sitting postures. Human Factors, 31:229-241, 1989.

Zacharkow, D.: Posture: Sitting, Standing, Chair Design and Exercise. Springfield, Thomas, 1988.

Zacharkow, D.: The problems with lumbar support. Physical Therapy Forum, 9(35):1,3-5, 1990.

Branton, P.: Behaviour, body mechanics and discomfort. In Grandjean, E. (Ed.): Proceedings of the Symposium on Sitting Posture. London, Taylor and Francis, 1969, pp. 202-213.

Sandover, J., and Dupuis, H.: A reanalysis of spinal motion during vibration. Ergonomics, 30:975-985, 1987.

McKenzie, R.A.: The Lumbar Spine. Mechanical Diagnosis and Therapy. Waikanae, Spinal Publications, 1981.

Humphry, G.M.: A Treatise on the Human Skeleton. Cambridge, MacMillan, 1858.

Wiles, P.: Postural deformities of the anteroposterior curves of the spine. The Lancet, 1:911-919, April 17, 1937.

Vulcan, A.P., King, A.I., and Nakamura, G.S.: Effects of bending on the vertebral column during +Gz acceleration. Aerospace Medicine, 41:294-300, 1970.

Alexander, C.J.: Scheuermann’s disease. Skeletal Radiology, 1:209-221, 1977.

Markolf, K.L.: Deformation of the thoracolumbar intervertebral joints in response to external loads. The Journal of Bone and Joint Surgery, 54-A:511-533, 1972.

White, A.A., and Panjabi, M.M.: Clinical Biomechanics of the Spine. Philadelphia, Lippincott, 1978, p.84.

Haynes, R.S.: Postural reflexes. American Journal of Diseases of Children, 36:1093-1107, 1928.

De Troyer, A.: Mechanical role of the abdominal muscles in relation to posture. Respiration Physiology, 53:341-353, 1983.

Watson, P.J., and Hixon, T.J.: Respiratory kinematics in classical (opera) singers. Journal of Speech and Hearing Research, 28:104-122, 1985.

Xie, A., Takasaki, Y., Popkin, J., Orr, D., and Bradley, T.D.: Chemical and postural influence on scalene and diaphragmatic activation in humans. Journal of Applied Physiology, 70:658-664, 1991.

Xie, A., Takasaki, Y., and Bradley, T.D.: Influence of body position on diaphragmatic and scalene activation during hypoxic rebreathing. Journal of Applied Physiology, 75:2234-2238, 1993.

Travell, J.G., and Simons, D.G.: Myofascial Pain and Dysfunction. Baltimore, Williams and Wilkins, 1983.

Narakas, A.O.: The role of thoracic outlet syndrome in the double crush syndrome. Annals of Hand and Upper Limb Surgery, 9:331-340, 1990.

Novak, C.B., Mackinnon, S.E., and Patterson, G.A.: Evaluation of patients with thoracic outlet syndrome. The Journal of Hand Surgery, 18A:292-299, 1993.

Mackinnon, S.E., and Novak, C.B.: Clinical commentary: patho-genesis of cumulative trauma disorder. The Journal of Hand Surgery, 19A:873-883, 1994.

Zacharkow, D.: Sitting posture: the overlooked factor in carpal tunnel syndrome. Advance for Physical Therapists, 5:8-9, 17, May 16, 1994.

Decima, E.E., von Euler, C., and Thoden, U.: Intercostal-to-phrenic reflexes in the spinal cat. Acta Physiologica Scandinavica, 75:568-579, 1969.

Leanderson, R., Sundberg, J., and von Euler, C.: Role of diaphragmatic activity during singing: a study of transdiaphragmatic pressures. Journal of Applied Physiology, 62:259-270, 1987.

Sarti, M.A., Monfort, M., Fuster, M.A., and Villaplana, L.A.: Muscle activity in upper and lower rectus abdominis during abdominal exercises. Archives of Physical Medicine and Rehabilitation, 77:1293-1297, 1996.

Floyd, W.F., and Silver, P.H.S.: Electromyographic study of pat-terns of activity of the anterior abdominal wall muscles in man. Journal of Anatomy, 84:132-145, 1950.

Lipetz, S., and Gutin, B.: An electromyographic study of four abdominal exercises. Medicine and Science in Sports, 2:35-38, 1970.

Frost, L.H.: Individual structural differences in the orthopedic examination. Journal of Health and Physical Education, 9:90-93,122, 1938.

Drew, L.C.: Individual Gymnastics, 5th ed. Philadelphia, Lea and Febiger, 1945.

De Troyer, A., Estenne, M., Ninane, V., Van Gansbeke, D., and Gorini M.: Transversus abdominis muscle function in humans. Journal of Applied Physiology, 68:1010-1016, 1990.

Cresswell, A.G., Grundström, H., and Thorstensson, A.: Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man. Acta Physiologica Scandinavica, 144:409-418, 1992.

Ono, K.: Electromyographic studies of the abdominal wall muscles in visceroptosis. The Tohoku Journal of Experimental Medicine, 68:347-354, 1958.

Hodges, P.W., and Richardson, C.A.: Inefficient muscular stabilization of the lumbar spine associated with low back pain. Spine, 21:2640-2650, 1996.

Keith, A.: Man’s posture: its evolution and disorders. Lecture four. The adaptations of the abdomen and of its viscera to the orthograde posture. The British Medical Journal, 1:587-590, 1923.

Parsons, C.A.: Use of wrist rests by data input VDU operators. In Lovesey, E.J. (Ed.): Contemporary Ergonomics. London, Taylor and Francis, 1991, pp.319-322.

Pascarelli, E.P., and Kella, J.J.: Soft-tissue injuries related to use of the computer keyboard. Journal of Occupational Medicine, 35:522-532, 1993.

Harvey, R., and Peper, E.: Surface electromyography and mouse use position. Ergonomics, 40:781-789, 1997.

Straker, L.M., Pollock, C.M., and Mangharam, J.E.: The effect of shoulder posture on performance, discomfort and muscle fatigue whilst working on a visual display unit. International Journal of Industrial Ergonomics, 20:1-10, 1997.

Mosher, E.M.: The influence of habitual posture on the symmetry and health of the body. The Brooklyn Medical Journal, 6:393-414, 1892.

Avon, G., and Schmitt, L.: Electromyographie du trapèze dans diverses positions de travail à la machine à écrire. Ergonomics, 18:619-626, 1975.

Stack, B.: Keyboard RSI: The Practical Solution. Hobart, Tasmania, Muden Publishing Company, 1987.

Werner, R., Armstrong, T.J., Bir, C., and Aylard, M.K.: Intracarpal canal pressures: the role of finger, hand, wrist and forearm position. Clinical Biomechanics, 12:44-51, 1997.

Pechan, J., and Julis, I.: The pressure measurement in the ulnar nerve. A contribution to the pathophysiology of the cubital tunnel syndrome. Journal of Biomechanics, 8:75-79, 1975.

Hedge, A., and Powers, J.R.: Wrist postures while keyboarding: effects of a negative slope keyboard system and full motion forearm supports. Ergonomics, 38:508-517, 1995.

DiVeta, J., Walker, M.L., and Skibinski, B.: Relationship between performance of selected scapular muscles and scapular abduction in standing subjects. Physical Therapy, 70:470-479, 1990.

Lovett, R.W.: Round shoulders and faulty attitude: a method of observation and record, with conclusions as to treatment. Boston Medical and Surgical Journal, 147:510-520, 1902.

Fahrner: Das Kind und der Schultisch. Zurich, Schulthess, 1865. Translated in Cohn, H.: The Hygiene of the Eye in Schools. London, Simpkin, Marshall and Co., 1886, pp. 94-98.

Sucher, B.M., and Heath, D.M.: Thoracic outlet syndrome—a myofascial variant: part three. Structural and postural considerations. The Journal of the American Osteopathic Association, 93:334, 340-345, 1993.

Sucher, B.M.: Thoracic outlet syndrome — a myofascial variant: part one. Pathology and diagnosis. The Journal of the American Osteopathic Association, 90:686-704, 1990.

Fleischer, A.G., Rademacher, U., and Windberg, H.J.: Individual characteristics of sitting behaviour. Ergonomics, 30:703-709, 1987.

Forssberg, H., and Hirschfeld, H.: Postural adjustments in sitting humans following external perturbations: muscle activity and kinematics. Experimental Brain Research, 97:515-527, 1994.

Bennett, H.E.: School Posture and Seating. Boston, Ginn and Company, 1928.

Helbig, K.: Sitzdruckverteilung beim ungepolsterten sitz. Anthropologischer Anzieger, 36:194-202, 1978.

Branton, P.: The Comfort of Easy Chairs. Stevenage, Hertfordshire, England, The Furniture Industry Research Association, 1966.

Bendix, T., Winkel, J., and Jessen, F.: Comparison of office chairs with fixed forwards or backwards inclining, or tiltable seats. European Journal of Applied Physiology, 54:378-385, 1985.

Freudenthal, A., van Riel, M.P.J.M., Molenbroek, J.F.M., and Snijders, C.J.: The effect on sitting posture of a desk with a ten-degree inclination using an adjustable chair and table. Applied Ergonomics, 22:329-336, 1991.

Jaschinski-Kruza, W.: Visual strain during VDU work: the effect of viewing distance and dark focus. Ergonomics, 31:1449-1465, 1988.

Grandjean, E.: Postures and the design of VDT workstations. Behaviour and Information Technology, 3:301-311, 1984.

Jaschinski-Kruza, W.: Eyestrain in VDU users: viewing distance and the resting position of ocular muscles. Human Factors, 33:69-83, 1991.

Jaschinski-Kruza, W.: On the preferred viewing distances to screen and document at VDU workplaces. Ergonomics, 33:1055-1063, 1990.

Coe, J.B.: The posture factor in repetitive stain injuries. In Ergonomics in New Zealand. Proceedings of the Inaugural Conference of the New Zealand Ergonomics Society. Palmerston North, New Zealand Ergonomics Society, 1987, pp. 114-124.

Sheedy, J.E., and Parsons, S.D.: Vision and the video display terminal: clinical findings. In Sauter, S., Dainoff, M., and Smith, M. (Eds.): Promoting Health and Productivity in the Computerized Office. London, Taylor and Francis, 1990, pp. 197-206.

Martin, D.K., and Dain, S.J.: Postural modifications of VDU operators wearing bifocal spectacles. Applied Ergonomics, 19:293-300, 1988

Goldman, J.M., Lehr, R.P., Millar, A.B., and Silver, J.R.: An electromyographic study of the abdominal muscles during postural and respiratory manoeuvres. Journal of Neurology, Neurosurgery, and Psychiatry, 50:866-869, 1987.

Strohl, K.P., Mead, J., Banzett, R.B., Loring, S.H., and Kosch, P.C.: Regional differences in abdominal muscle activity during various maneuvers in humans. Journal of Applied Physiology, 51:1471-1476, 1981.

O’Sullivan, P.B., Twomey, L., Allison, G.T., Sinclair, J., Miller, K., and Knox, J.: Altered patterns of abdominal muscle activation in patients with chronic low back pain. Australian Journal of Physiotherapy, 43:91-98, 1997.

Rathbone, J.L., and Hunt, V.V.: Corrective Physical Education, 7th ed. Philadelphia, Saunders, 1965.

Cotton, F.J.: School furniture for Boston schools. American Physical Education Review, 9:267-284, 1904.

Dempster, W.T.: The anthropometry of body action. Annals of the New York Academy of Sciences, 63:559-585, 1955.

Branton, P., and Grayson, G.: An evaluation of train seats by observation of sitting behaviour. Ergonomics, 10:35-51, 1967.

Wong, E., Lee, G., Zucherman, J., and Mason, D.T.: Successful management of female office workers with “repetitive stress injury” or “carpal tunnel syndrome” by a new treatment modality —application of low level laser. International Journal of Clinical Pharmacology and Therapeutics, 33:208-211, 1995.

Farfan, H.F., and Baldwin, J.: Tired neck syndrome: chronic postural strain. In Karwowski, W. (Ed.): Trends in Ergonomics/Hu-man Factors III. Amsterdam, Elsevier Science, 1986, pp. 651-658.

Harms-Ringdahl, K., and Ekholm, J.: Intensity and character of pain and muscular activity levels elicited by maintained extreme flexion position of the lower-cervical-upper-thoracic spine. Scandinavian Journal of Rehabilitation Medicine, 18:117-126, 1986.

O’Gorman, H., and Jull, G.: Thoracic kyphosis and mobility: the effect of age. Physiotherapy Practice, 3:154-162, 1987.

Cutler, W.B., Friedmann, E., and Genovese-Stone, E.: Prevalence of kyphosis in a healthy sample of pre- and postmenopausal women. American Journal of Physical Medicine and Rehabilitation, 72:219-225, 1993.

Takahashi, C.: Office chair encourages “active sitting.” The Wall Street Journal, July 21, 1997, pp. B-1, B-10.

Evans, E.: Ergonomic aspects of the driving position—a postural analysis. In Ergonomics in the Tourist, Agricultural and Mining Industries. Proceedings of the 22nd Annual Conference of the Ergonomics Society of Australia and New Zealand. Carlton South, Victoria, Australia, ESANZ, 1985, pp. 250-255.

Keegan, J.J.: Alterations of the lumbar curve related to posture and seating. The Journal of Bone and Joint Surgery, 35-A:589-603, 1953.

Holm, S., and Nachemson, A.: Variations in the nutrition of the canine intervertebral disc induced by motion. Spine, 8:866-874, 1983.

Helander, M.G., and Quance, L.A.: Effect of work-rest schedules on spinal shrinkage in the sedentary worker. Applied Ergonomics, 21:279-284, 1990.

Bhatnager, V., Drury, C.G., and Schiro, S.G.: Posture, postural discomfort, and performance. Human Factors, 27:189-199, 1985.

Grandjean, E., Jenni, M., and Rhiner, A.: Eine indirekte methode zur erfassung des komfortgefühls beim sitzen. Internationale Zeitschrift für Angewandte Physiologie Einschliesslich Arbeits-physiologie, 18: 101-106, 1960.

Mosher, E.M.: Hygienic desks for school children. Educational Review, 18:9-14, 1899.

Stewart, P.C., and McQuilton, G.: Straddle seating for the cerebral palsied child. Physiotherapy, 73:204-206, 1987.

Kellogg, J.H.: Physical deterioration resulting from school life; cause; remedy. Proceedings of the National Education Association, 1896, pp. 899-911.

Darby, F.W.: Visual Display Unit Operators: A Study of Their Postures and Workstations. Department of Health, Southern Regional Occupational Health Unit, Wellington, New Zealand, 1984.

Taylor, H.L.: Results of research on conditions affecting posture. Journal of the American Medical Association, 68:327-330, 1917.

Romaniuk, J.R., Supinski, G.S., and DiMarco, A.F.: Reflex control of diaphragm activation by thoracic afferents. Journal of Applied Physiology, 75:63-69, 1993.

Remmers, J.E.: Extra-segmental reflexes derived from intercostal afferents: phrenic and laryngeal responses. Journal of Physiology, 233:45-62, 1973.

Branton, P.: Backshapes of seated persons—how close can the interface be designed? Applied Ergonomics, 15:105-107, 1984.

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