This study investigated the effect of static or dynamic back extensors endurance exercise in combination with McKenzie Protocol (MP) in patients with Long-term Mechanical Low-Back Pain (LMLBP). This randomized controlled trial involved 84 patients, who were assigned into MP Group (MPG), MP plus Static Back Extensors Endurance (SBEE) Exercise Group (MPSBEEG), or MP plus Dynamic Back Extensors’ Endurance (DBEE) Exercise Group (MPDBEEG). Twenty-five, 22, and 20 participants in MPG, MPSBEEG, and MPDBEEG, respectively, completed the thrice weekly eight-week study (drop-out rate = 20.2%) and outcomes were measured in terms of SBEE, DBEE, and Back Muscles Fatigue (BMF) at the 4th and 8th week, respectively. There were significant differences in groups mean change scores on SBEE ( , and ？sec), DBEE ( , , and rep), and BMF ( , , and ) at week 4, and SBEE ( , , and ？sec), DBEE ( , , and reps), BMF ( , , and ) at week 8, respectively ( ). It was concluded that MP alone, or in combination with SBEE or DBEE, exercise was effective in the rehabilitation of back extensors’ endurance and fatigability in patients with LMLBP. However, the addition of SBEE to MP led to significantly higher positive effects. 1. Introduction Long-term mechanical low-back pain (LBP) results in inhibition and atrophy of the deep segmental muscles such as multifidus and overactivity of the longer superficial muscles of the trunk with resultant decreased dynamic activity and increased fatiguibility [1–4]. Long-term mechanical LBP is more difficult to treat [5–7] and treatment outcomes give variable results [8–10] and it consequently results in both physical and psychological deconditionings that trap the patient in a vicious circle characterized with decreased physical performance, exacerbated nociceptive sensations, depression, impaired social functioning, and work disability [11]. One of the more commonly used physical therapy approaches in the management of long-term mechanical LBP with documented effectiveness is the McKenzie Protocol (MP) [12–15]; However, there seems to be inconclusive evidence whether the MP addresses the accompanying back muscles inhibition in patients with long-term mechanical LBP. Some studies considered the McKenzie’s extension exercises as passive and presumably opined that it may not counter the back muscles’ inhibition and atrophy resulting from long-term LBP [16–18], however, a study by Fiebert and Keller [19] among apparently healthy individuals demonstrated that the McKenzie’s extension exercises were not truly passive for lumbar back extensor muscles. On the
References
[1]
T. Sihvonen, J. Partanen, O. Hanninen, and S. Soimakallio, “Electric behavior of low back muscles during lumbar pelvic rhythm in low back pain patients and healthy controls,” Archives of Physical Medicine and Rehabilitation, vol. 72, no. 13, pp. 1080–1087, 1991.
[2]
J. E. Cassisi, M. E. Robinson, P. O'Conner, and M. MacMillan, “Trunk strength and lumbar paraspinal muscle activity during isometric exercise in chronic low-back pain patients and controls,” Spine, vol. 18, no. 2, pp. 245–251, 1993.
[3]
T. Sihvonen, M. Huttunen, M. Makkonen, and O. Airaksinen, “Functional changes in back muscle activity correlate with pain intensity and prediction of low back pain during pregnancy,” Archives of Physical Medicine and Rehabilitation, vol. 79, no. 10, pp. 1210–1212, 1998.
[4]
C. Richardson, G. Jull, P. Hodges, and J. Hides, Therapeutic Exercise for Spinal Segmental Stabilization in Low Back Pain, Churchill Livingstone, London, UK, 1999.
[5]
J. T. Cottingham and J. Maitland, “A three-paradigm treatment model using soft tissue mobilization and guided movement-awareness techniques for a patient with chronic low back pain: a case study,” Journal of Orthopaedic and Sports Physical Therapy, vol. 26, no. 3, pp. 155–167, 1997.
[6]
J. Hildebrandt, M. Pfingsten, P. Saur, and J. Jansen, “Prediction of success from a multidisciplinary treatment programme for chronic low-back pain,” Spine, vol. 22, no. 1, pp. 990–1001, 1997.
[7]
H. Frost, S. E. Lamb, and C. H. Shackleton, “A functional restoration programme for chronic low back pain,” Physiotherapy, vol. 86, no. 6, pp. 285–293, 2000.
[8]
Clinical Standards Advisory Group CSAG, Report on Back Pain, HMSO, London, UK, 1994.
[9]
J. Rainville, J. Sobel, C. Hartigan, G. Monlux, and J. Bean, “Decreasing disability in chronic back pain through aggressive spine rehabilitation,” Journal of Rehabilitation Research and Development, vol. 34, no. 4, pp. 383–393, 1997.
[10]
D. M. Carpenter and B. W. Nelson, “Low back strengthening for the prevention and treatment of low back pain,” Medicine and Science in Sports and Exercise, vol. 31, no. 1, pp. 18–24, 1999.
[11]
C. Demoulin, M. Vanderthommen, C. Duysens, and J.-M. Crielaard, “Spinal muscle evaluation using the Sorensen test: a critical appraisal of the literature,” Joint Bone Spine, vol. 73, no. 1, pp. 43–50, 2006.
[12]
D. C. Cherkin, R. A. Deyo, M. Battié, J. Street, and W. Barlow, “A comparison of physical therapy, chiropractic manipulation, and provision of an educational booklet for the treatment of patients with low back pain,” The New England Journal of Medicine, vol. 339, no. 15, pp. 1021–1029, 1998.
[13]
R. McKenzie and S. May, The Lumbar Spine. Mechanical Diagnosis & Therapy, vol. 1, Spinal Publications, Waikanae, New Zealand, 2nd edition, 2003.
[14]
L. A. Carneiro Machado, M. V. S. De Souza, P. H. Ferreira, and M. L. Ferreira, “The McKenzie method for low back pain: a systematic review of the literature with a meta-analysis approach,” Spine, vol. 31, no. 9, pp. E254–E262, 2006.
[15]
O. Ayanniyi, O. T. Lasisi, B. O. A. Adegoke, and M. O. Oni-Orisan, “Management of low back pain: attitudes and treatment preferences of physiotherapists in Nigeria,” African Journal of Biomedical Research, vol. 101, pp. 41–49, 2007.
[16]
R. Donelson, G. Silva, and K. Murphy, “Centralization phenomenon. It usefulness in evaluating and treating referred pain,” Spine, vol. 15, no. 3, pp. 211–213, 1990.
[17]
M. R. Bookhout, “Biomechanical assessment of low back pain,” Journal of Back Back Musculoskeletal Rehabilitation, vol. 1, pp. 33–45, 1991.
[18]
M. R. Underwood, “Patients' beliefs as to the cause of their low back pain,” Journal of Back and Musculoskeletal Rehabilitation, vol. 9, no. 1, pp. 65–67, 1997.
[19]
I. Fiebert and C. D. Keller, “Are “passive” extension exercises really passive?” Journal of Orthopaedic and Sports Physical Therapy, vol. 19, no. 2, pp. 111–116, 1994.
[20]
F. Biering-Sorensen, “Physical measurements as risk indicators for low-back trouble over a one-year period,” Spine, vol. 9, no. 2, pp. 106–119, 1984.
[21]
S. V. Risch, N. K. Norvell, M. L. Pollock et al., “Lumbar strengthening in chronic low back pain patients: physiologic and psychological benefits,” Spine, vol. 18, no. 2, pp. 232–238, 1993.
[22]
S. Luoto, M. Heli？vaara, H. Hurri, and H. Alaranta, “Static back endurance and the risk of low-back pain,” Clinical Biomechanics, vol. 10, no. 6, pp. 323–324, 1995.
[23]
J. Mayer, V. Mooney, and S. Dagenais, “Evidence-informed management of chronic low back pain with lumbar extensor strengthening exercises,” Spine Journal, vol. 8, no. 1, pp. 96–113, 2008.
[24]
P. Plum and J. F. Rehfeld, “Muscular training for acute and chronic back pain,” The Lancet, vol. 1, no. 8426, pp. 453–454, 1985.
[25]
M. T. Moffroid, L. D. Haugh, A. J. Haig, S. M. Henry, and M. H. Pope, “Endurance training of trunk extensor muscles,” Physical Therapy, vol. 73, no. 1, pp. 10–17, 1993.
[26]
S. M. LeFort and T. E. Hannah, “Return to work following an aquafitness and muscle strengthening program for the low back injured,” Archives of Physical Medicine and Rehabilitation, vol. 75, no. 11, pp. 1247–1255, 1994.
[27]
B. Chok, R. Lee, J. Latimer, and S. B. Tan, “Endurance training of the trunk extensor muscles in people with subacute low back pain,” Physical Therapy, vol. 79, no. 11, pp. 1032–1042, 1999.
[28]
B. Holmes, S. Leggett, V. Mooney, J. Nichols, S. Negri, and A. Hoeyberghs, “Comparison of female geriatric lumbar-extension strength: asymptotic versus chronic low back pain patients and their response to active rehabilitation,” Journal of Spinal Disorders, vol. 9, no. 1, pp. 17–22, 1996.
[29]
B. W. Nelson, D. M. Carpenter, T. E. Dreisinger, M. Mitchell, C. E. Kelly, and J. A. Wegner, “Can spinal surgery be prevented by aggressive strengthening exercises? A prospective study of cervical and lumbar patients,” Archives of Physical Medicine and Rehabilitation, vol. 80, no. 1, pp. 20–25, 1999.
[30]
M. L. Pollock, S. H. Leggett, J. E. Graves, A. Jones, M. Fulton, and J. Cirulli, “Effect of resistance training on lumbar extension strength,” American Journal of Sports Medicine, vol. 17, no. 5, pp. 624–629, 1989.
[31]
B. E. Udermann, J. M. Mayer, J. E. Graves, and S. R. Murray, “Quantitative assessment of lumbar paraspinal muscle endurance,” Journal of Athletic Training, vol. 38, no. 3, pp. 259–262, 2003.
[32]
D. A. Thompson, Sensitivity of paraspinal EMG spectral analysis to training. Two preliminary studies [Doctoral thesis], Queens University, Kingston, Canada, 1992.
[33]
J. P. Leigh and R. M. Sheetz, “Prevalence of back pain among fulltime United States workers,” British Journal of Industrial Medicine, vol. 46, no. 9, pp. 651–657, 1989.
[34]
C. N. Burnett, T. M. Glenn, C. Kisner, and L. A. Colby, “Principles of aerobic exercise,” in Therapeutic Exercise: Foundations and Techniques, pp. 111–142, Jaypee Brothers, New Delhi, India, 3rd edition, 1996.
[35]
R. A. McKenzie, The Lumbar Spine: Mechanical Diagnosis and Therapy Spinal Publication, Spinal Publication, Waikanae, New Zealand, 1981.
[36]
V. Mora, “Chronic mechanical back pain strategies for intervention when conservative treatment fails,” Journal of the American Academy of Physician Assistants, vol. 17, no. 7, pp. 12–16, 2004.
[37]
G. Waddell, “Low back pain: a twentieth century health care enigma,” Spine, vol. 21, no. 24, pp. 2820–2825, 1996.
[38]
G. A. V. Borg, “Psychophysical bases of perceived exertion,” Medicine and Science in Sports and Exercise, vol. 14, no. 5, pp. 377–381, 1982.
[39]
H. Alaranta, “Strength and endurance testing,” in The Clinical Application of Outcomes Assessment, S. G. Yeomans, Ed., pp. 158–162, Appleton & Lange, Stamford, Calif, USA, 2000.
[40]
C. E. Mbada, O. Ayanniyi, and S. O. Ogunlade, “Effect of static and dynamic back extensor muscles endurance exercise on pain intensity, activity limitation and participation restriction in patients with Long-Term Mechanical Low-Back Pain,” Rehabilitacja Medyczna, vol. 15, no. 3, pp. 11–20, 2011.
[41]
J. D. Childs, J. M. Fritz, T. W. Flynn et al., “A clinical prediction rule to identify patients with low back pain most likely to benefit from spinal manipulation: a validation study,” Annals of Internal Medicine, vol. 141, no. 12, pp. 1032–1042, 2004.
[42]
E. M. Hagen, E. Svensen, and H. R. Eriksen, “Predictors and modifiers of treatment effect influencing sick leave in subacute low back pain patients,” Spine, vol. 30, no. 24, pp. 2717–2723, 2005.
[43]
M. R. Underwood, V. Morton, and A. Farrin, “Do baseline characteristics predict response to treatment for low back pain? Secondary analysis of the UK BEAM dataset [ISRCTN32683578],” Rheumatology, vol. 46, no. 8, pp. 1297–1302, 2007.
[44]
R. Stankovic and O. Johnell, “Conservative treatment of acute low-back pain. A prospective randomized trial: McKenzie method of treatment versus patient education in “mini back school”,” Spine, vol. 15, no. 2, pp. 120–123, 1990.
[45]
T. Reddeck, “An evaluation of the McKenzie regimen-validity of the disc model,” in Proceedings of the 10th Biennial Conference of Manipulative Physiotherapists Association of Australia, Melbourne, Autralia, November 1997.
[46]
University of Iowa UoI, “Biological Link Between Pain and Fatigue Discovered,” 2008, http://www.sciencedaily.com/.
[47]
R. B. Armstrong, “Mechanism of exercise-induced delayed onset muscular soreness: a brief review,” Medicine and Science in Sports and Exercise, vol. 16, no. 6, pp. 529–538, 1984.
[48]
S. H. Roy and L. I. E. Oddsson, “Classification of paraspinal muscle impairments by surface electromyography,” Physical Therapy, vol. 78, no. 8, pp. 838–851, 1998.
[49]
C. Manniche, L. Bentzen, G. Hesselsoe, I. Christensen, and E. Lundberg, “Clinical trial for intensive muscle training for chronic low back pain,” The Lancet, vol. 2, no. 8626-8627, pp. 1473–1476, 1988.
[50]
I. Lindstr？m, C. Ohlund, C. Eek, L. Wallin, L.-E. Peterson, and A. Nachemson, “Mobility, strength, and fitness after a graded activity program for patients with subacute low back pain: a randomized prospective clinical study with a behavioral therapy approach,” Spine, vol. 17, no. 6, pp. 641–652, 1992.
[51]
B. Gundewall, M. Liljeqvist, and T. Hansson, “Primary prevention of back symptoms and absence from work: a prospective randomized study among hospital employees,” Spine, vol. 18, no. 5, pp. 587–594, 1993.
[52]
M. T. Moffroid, “Endurance of trunk muscles in persons with chronic low back pain: assessment, performance, training,” Journal of Rehabilitation Research and Development, vol. 34, no. 4, pp. 440–447, 1997.
[53]
M. Kj？r, “Role of extracellular matrix in adaptation of tendon and skeletal muscle to mechanical loading,” Physiological Reviews, vol. 84, no. 2, pp. 649–698, 2004.
[54]
D. J. Pearsall and J. G. Reid, “Line of gravity relative to upright vertebral posture,” Clinical Biomechanics, vol. 7, no. 2, pp. 80–86, 1992.
[55]
P. B. O'Sullivan, K. M. Grahamslaw, M. Kendell, S. C. Lapenskie, N. E. M？ller, and K. V. Richards, “The effect of different standing and sitting postures on trunk muscle activity in a pain-free population,” Spine, vol. 27, no. 11, pp. 1238–1244, 2002.
[56]
S. M. McGill, R. L. Hughson, and K. Parks, “Changes in lumbar lordosis modify the role of the extensor muscles,” Clinical Biomechanics, vol. 15, no. 10, pp. 777–780, 2000.
[57]
T. M. Cook, S. Mann, and G. E. Lovested, “Dynamic comparison of the two-hand stoop and assisted one-hand lift methods,” Journal of Safety Research, vol. 21, no. 2, pp. 53–59, 1990.
[58]
S. M. McGill, “Electromyographic activity of the abdominal and low back musculature during the generation of isometric and dynamic axial trunk torque: implications for lumbar mechanics,” Journal of Orthopaedic Research, vol. 9, no. 1, pp. 91–103, 1991.
[59]
R. S. Delitto and S. J. Rose, “An electromyographic analysis of two techniques for squat lifting and lowering,” Physical Therapy, vol. 72, no. 6, pp. 438–448, 1992.
[60]
J. L. Kelsey, P. B. Githens, and T. O'Conner, “Acute prolapsed lumbar intervertebral disc. An epidemiologic study with special reference to driving automobiles and cigarette smoking,” Spine, vol. 9, no. 6, pp. 608–613, 1984.
[61]
M. A. Adams and W. C. Hutton, “The effect of posture on the role of the apophysial joints in resisting intervertebral compressive forces,” Journal of Bone and Joint Surgery. British, vol. 62, no. 3, pp. 358–362, 1980.
[62]
M. A. Adams, D. W. McMillan, T. P. Green, and P. Dolan, “Sustained loading generates stress concentrations in lumbar intervertebral discs,” Spine, vol. 21, no. 4, pp. 434–438, 1996.
[63]
M. Kankaanp？？, S. Taimela, C. L. Webber Jr., O. Airaksinen, and O. H？nninen, “Lumbar paraspinal muscle fatigability in repetitive isoinertial loading: EMG spectral indices, Borg scale and endurance time,” European Journal of Applied Physiology and Occupational Physiology, vol. 76, no. 3, pp. 236–242, 1997.
[64]
C. Krogh-Lund and K. Jorgensen, “Modification of myo-electric power spectrum in fatigue from 15% maximal voluntary contraction of human elbow flexor muscles, to limit of endurance: reflection of conduction velocity variation and/or centrally mediated mechanisms?” European Journal of Applied Physiology and Occupational Physiology, vol. 64, no. 4, pp. 359–370, 1992.
[65]
A. G. Crenshaw, S. Karlsson, B. Gerdle, and J. Friden, “Differential responses in intramuscular pressure and EMG fatigue indicators during low- vs. high-level isometric contractions to fatigue,” Acta Physiologica Scandinavica, vol. 160, no. 4, pp. 353–361, 1997.
[66]
C. Manniche, E. Lundberg, I. Christensen, L. Bentzen, and G. Hessels？e, “Intensive dynamic back exercises for chronic low back pain: a clinical trial,” Pain, vol. 47, no. 1, pp. 53–63, 1991.
[67]
H. W. Lee, “Progressive muscle synergy and synchronization in movement patterns: an approach to the treatment of dynamic lumbar instability,” Journal of Manual and Manipulative Therapy, vol. 2, pp. 133–142, 1994.
[68]
D. S. Elia, R. W. Bohannon, D. Cameron, and R. C. Albro, “Dynamic pelvic stabilization during hip flexion: a comparison study,” Journal of Orthopaedic and Sports Physical Therapy, vol. 24, no. 1, pp. 30–36, 1996.
[69]
H. Bentsen, F. Lindg？rde, and R. Manthorpe, “The effect of dynamic strength back exercise and/or a home training program in 57-year-old women with chronic law back pain. Results of a prospective randomized study with a 3-year follow-up period,” Spine, vol. 22, no. 13, pp. 1494–1500, 1997.
[70]
F. Johannsen, L. Remvig, P. Kryger et al., “Exercises for chronic low back pain: a clinical trial,” Journal of Orthopaedic and Sports Physical Therapy, vol. 22, no. 2, pp. 52–59, 1995.
[71]
J. P. A. Arokoski, M. Kankaanp？？, T. Valta et al., “Back and hip extensor muscle function during therapeutic exercises,” Archives of Physical Medicine and Rehabilitation, vol. 80, no. 7, pp. 842–850, 1999.
[72]
S. M. McGill, A. Childs, and C. Liebenson, “Endurance times for low back stabilization exercises: clinical targets for testing and training from a normal database,” Archives of Physical Medicine and Rehabilitation, vol. 80, no. 8, pp. 941–944, 1999.
[73]
E. Zinzen, D. Caboor, M. Verlinden et al., “Will the use of different prevalence rates influence the development of a primary prevention programme for low-back problems?” Ergonomics, vol. 43, no. 10, pp. 1789–1803, 2000.
[74]
W. S. Marras, K. G. Davis, and K. P. Granata, “Trunk muscle activities during asymmetric twisting motions,” Journal of Electromyography and Kinesiology, vol. 8, no. 4, pp. 247–256, 1998.
[75]
R. E. Seroussi and M. H. Pope, “The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes,” Journal of Biomechanics, vol. 20, no. 2, pp. 135–146, 1987.
[76]
C. Pinupong, Effects of isometric and dynamic endurance training on fatigability of back extensor muscle in male [Ph.D. thesis], 2005, submitted in a partial fulfilment of the requirements for the degree of master of science physiotherapy of the faculty of graduate studies Mahidol university.
[77]
J. Cholewicki and S. M. McGill, “Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain,” Clinical Biomechanics, vol. 11, no. 1, pp. 1–15, 1996.
[78]
P. B. O'Sullivan, L. Twomey, and C. T. Allison, “Dysfunction of the neuro-muscular system in the presence of low back pain-implications for physical therapy management,” Journal of Manual and Manipulative Therapy, vol. 5, no. 1, pp. 20–26, 1997.
[79]
D. J. Ponte, G. J. Jensen, and B. E. Kent, “A preliminary report on the use of the McKenzie protocol versus Williams protocol in the treatment of low back pain,” Journal of Orthopaedic and Sports Physical Therapy, vol. 6, no. 2, pp. 130–139, 1984.
[80]
J. R. Kopp, A. H. Alexander, and R. H. Turocy, “The use of lumbar extension in the evaluation and treatment of patients with acute herniated nucleus pulposus. A preliminary report,” Clinical Orthopaedics and Related Research, vol. 202, pp. 211–218, 1986.
[81]
A. H. Alexander, A. M. Jones, and D. H. Rosenbaum Jr., “Nonoperative management of herniated nucleus pulposus: patient selection by the extension sign: long-term follow-up,” Orthopaedic Review, vol. 21, no. 2, pp. 181–188, 1992.
[82]
G. Nwuga and V. C. B. Nwuga, “Relative therapeutic efficacy of the Williams and McKenzie protocols in back pain management,” Physiotherapy Practice, vol. 1, no. 2, pp. 99–105, 1985.
[83]
H. Frost, J. A. Klaber Moffett, J. S. Moser, and J. C. T. Fairbank, “Randomised controlled trial for evaluation of fitness programme for patients with chronic low back pain,” British Medical Journal, vol. 310, no. 6973, pp. 151–154, 1995.
[84]
M. Kankaanp？？, S. Taimela, O. Airaksinen, and O. H？nninen, “The efficacy of active rehabilitation in chronic low back pain: effect on pain intensity, self-experienced disability, and lumbar fatigability,” Spine, vol. 24, no. 10, pp. 1034–1042, 1999.
[85]
J. Rainville, C. A. Jouve, C. Hartigan, E. Martinez, and M. Hipona, “Comparison of short- and long-term outcomes for aggressive spine rehabilitation delivered two versus three times per week,” Spine Journal, vol. 2, no. 6, pp. 402–407, 2002.
[86]
J. Rainville, C. Hartigan, E. Martinez, J. Limke, C. Jouve, and M. Finno, “Exercise as a treatment for chronic low back pain,” Spine Journal, vol. 4, no. 1, pp. 106–115, 2004.
[87]
D. K. Ahern, D. J. Hannon, A. J. Goreczny, M. J. Follick, and J. R. Parziale, “Correlation of chronic low-back pain behavior and muscle function examination of the flexion-relaxation response,” Spine, vol. 15, no. 2, pp. 92–95, 1990.
[88]
J. Rainville, D. K. Ahern, and L. Phalen, “Altering beliefs about pain and impairment in a functionally oriented treatment program for chronic low back pain,” Clinical Journal of Pain, vol. 9, no. 3, pp. 196–201, 1993.
[89]
A. Rissanen, H. Kalimo, H. Alaranta, and R. G. Hazard, “Effect of intensive training on the isokinetic strength and structure of lumbar muscles in patients with chronic low back pain,” Spine, vol. 20, no. 3, pp. 333–340, 1995.
[90]
B. O. A. Adegoke and F. O. Babatunde, “Effect of an exercise protocol on the endurance of trunk extensor muscles—a randomized control trial,” Hong Kong Physiotherapy Journal, vol. 25, pp. 2–9, 2007.
[91]
A. F. Mannion, S. Taimela, M. Müntener, and J. Dvorak, “Active therapy for chronic low back pain part 1. Effects on back muscle activation, fatigability, and strength,” Spine, vol. 26, no. 8, pp. 897–908, 2001.
[92]
T. Petersen, P. Kryger, C. Ekdahl, S. Olsen, and S. Jacobsen, “The effect of McKenzie therapy as compared with that of intensive strengthening training for the treatment of patients with subacute or chronic low back pain: a randomized controlled trial,” Spine, vol. 27, no. 16, pp. 1702–1708, 2002.
[93]
B. E. Udermann, J. M. Mayer, R. G. Donelson, J. E. Graves, and S. R. Murray, “Combining lumbar extension training with McKenzie therapy: effects on pain; disability; and psychosocial functioning in chronic low back pain patients,” Gundersen Lutheran Medical Journal, vol. 32, pp. 7–12, 2004.
[94]
W. D. McArdle, F. I. Katch, and V. L. Katch, Exercise Physiology, Williams & Wilkins, Baltimore, Md, USA, 4th edition, 1996.
