Spinal muscle evaluation using the Sorensen test: a critical appraisal of the literature

Joint Bone Spine 73 (2006) 43–50 http://france.elsevier.com/direct/BONSOI/

Review

Spinal muscle evaluation using the Sorensen test: a critical appraisal of the literature Christophe Demoulin *, Marc Vanderthommen, Christophe Duysens, Jean-Michel Crielaard Physical Medicine and Rehabilitation Unit, Liège University, Liège, Belgium Received 3 May 2004; accepted 4 August 2004 Available online 05 October 2004

Abstract The first test for evaluating the isometric endurance of trunk extensor muscles was described by Hansen in 1964. In 1984, following a study by Biering-Sorensen, this test became known as the “Sorensen test” and gained considerable popularity as a tool reported to predict low back pain within the next year in males. The test consists in measuring the amount of time a person can hold the unsupported upper body in a horizontal prone position with the lower body fixed to the examining table. This test has been used in many studies, either in its original version or as variants. Although its discriminative validity, reproducibility, and safety seem good, debate continues to surround its ability to predict low back pain; in addition, the gender-related difference in position-holding time remains unexplained and the influence of body weight unclear. A contribution of the hip extensor muscles to position holding has been established, but its magnitude remains unknown. The influence of personal factors such as motivation complicates the interpretation of the results. Despite these drawbacks, the Sorensen test has become the tool of reference for evaluating muscle performance in patients with low back pain, most notably before and after rehabilitation programs. © 2005 Elsevier SAS. All rights reserved. Keywords: Muscle endurance; Low back pain; Trunk extensor muscles; Physical evaluation; Spinal muscles

1. Introduction Despite growing research efforts, nonspecific low back pain remains a major public health burden throughout the industrialized world. Epidemiological data indicate an annual prevalence of about 39–54% [1,2] and a lifetime prevalence of 60–65% [1–3]. Costs to society stem mainly from chronic forms, which account for only 5–10% of cases [4,5]. Chronic nonspecific low back pain results in both physical and psychological deconditioning that traps the patient in a vicious circle characterized by decreased physical performance, exacerbated nociceptive sensations, impaired social functioning, work disability, and depression. The physical component of deconditioning involves both stiffness of the lumbar spinepelvic-femoral unit, decreased muscle strength and endurance, loss of cardiorespiratory adjustment to physical exertion, and neuromuscular inhibition (kinesiophobia) [6]. * Corresponding author. Département de Médecine Physique et Kinésithérapie-Réadaptation, ISEPK, B21, Allée des Sports 4, B-4000 Liege, Sart Tilman, Belgium. E-mail address: [email protected] (C. Demoulin). 1297-319X/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.jbspin.2004.08.002

Several studies suggest that patients with chronic nonspecific low back pain may benefit from an active multidisciplinary approach involving an individually tailored reconditioning program [6–8]. Tools capable of quantitating individual deficiencies and of documenting the effects of reconditioning would be useful. Evaluating the endurance of trunk extensor muscles seems to have greater discriminative validity than evaluation of maximal voluntary contractile force [9–14]. In 1964, Hansen developed the first test for evaluating the isometric endurance of trunk extensor muscles and validated it in 168 healthy individuals and 90 patients who had had surgery for low back pain within the last 3–4 weeks [15]. In this test, the patient is in the prone position with the lower body fixed to the examining table and the upper body extending beyond the edge of the table. The test consists in holding the upper body horizontal as long as possible. In 1972, Troup et al. evaluated muscle fatigability by performing surface electromyography in patients during the test [16]. After a 1984 study by Biering-Sorensen [9] published in Spine, the test became known as the “Sorensen test”. Biering-Sorensen

44

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

used the test together with several other evaluations in over 900 individuals and concluded that a shorter positionholding time during the Sorensen test predicted low back pain within the next year in males.

2. Methods We conducted a Medline search for articles reporting the use of the Sorensen test to evaluate the back muscles. The keywords used for the search were “Sorensen test”, “back pain”, “muscle endurance”, “static endurance”, “muscle fatigue”, “function test”, “back extension”, and “trunk extensors”. In addition, the reference list of each article retrieved by the Medline search was examined for additional related articles.

3. Description of the Sorensen test The patient lies on the examining table in the prone position with the upper edge of the iliac crests aligned with the edge of the table. The lower body is fixed to the table by three straps, located around the pelvis, knees, and ankles, respectively. With the arms folded across the chest, the patient is asked to isometrically maintain the upper body in a horizontal position (Fig. 1). The time during which the patient keeps the upper body straight and horizontal is recorded. In patients who experience no difficulty in holding the position, the test is stopped after 240 s. The Sorensen test is the most widely used test in published studies evaluating the isometric endurance of trunk extensor muscles. It has been used either as described initially or with a number of modifications, as listed below. • Arm position: the test has been used with the arms bent, the elbows held out, and the hands on the ears [17], forehead [18], or nape of the neck [19,20]; in another variant, the arms are held along the sides [13,21,22]. Because arm position influences the location of the center of gravity, these modifications affect the mass moment of the upper body and, therefore, test performance [23]. • Location of the edge of the table: in several studies, the anterior–superior iliac spines were placed at the edge of the table, instead of the upper edge of the iliac crests [24,25].

Fig. 1. The original Sorensen test.

• Number of straps: two [19,26–28] to five straps [14] have been used to hold the lower body to the table; in the Roman chair variant (Fig. 2), the feet are fixed to the device and no straps are needed [29–34]. • Starting position: in several studies [31,34], the test was started with the upper body sloping downward toward the floor so that a concentric contraction of the trunk extensor muscles was needed initially to reach the horizontal position. • Hip flexion: in theory, the hips remain fully extended throughout the Sorensen test. However, hip flexion was 6° in a study by Holmstrom et al. [10] and 40° in a study by Dedering et al. [29,30] (Fig. 3). • Method for documenting the horizontal position of the upper body: whereas many authors (including BieringSorensen) simply trusted a visual evaluation [10,19,21,27, 31,34–36], others used measurement devices (inclinometer [24,37,38], goniometer [18], or photoelectric cell [10,39]) or asked the patient to maintain contact between the back and a stadiometer or weight hanging from the ceiling [18,40,41]. • Criteria for stopping the test: in studies that used measurement devices or contact with an object to define the horizontal position, specific test-stopping criteria were used, such as trunk downsloping by more than 5–10° [24,37,42] or loss of contact with the object for more than 10 s [43].

Fig. 2. Roman chair used to evaluate isometric endurance of the trunk extensor muscles.

Fig. 3. Evaluation of the trunk extensor muscles as suggested by Dedering et al [29].

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

45

Table 1 Results of the Sorensen test reported in the literature Endurance (s)

Males Prior LBP

Healthy Biering-Sorensen [9] n > 900 Holmstrom et al. [10] n = 203 Mannion and Dolan [35] n = 229 Hultman et al. [39] n = 148 Mannion et al. [44] n = 200

Alaranta et al. [21] n = 475 Latimer et al. [24] n = 63 Simmonds et al. [22] n = 92

198 a 171.5 a 116 a 150 a

176 b 166.7 a

LBP

Healthy

163 137.5 b

197

Females Prior LBP

Current LBP 177

210

142 b 136 a

No LBP 100 132.6 a 77.8 a

85 b 141.7 a Males and females Prior LBP 85 107.7 b

123 a Current LBP 85*–99** 94.6 b 39.5 b

The position-holding times are given in seconds; n is the number of individuals in the study; and LBP means low back pain. * and ** indicate populations of LBP patients with and without an impact of their disease on their daily activities. Different letters in superscript indicate significant differences (P < 0.05).

• Test duration: some individuals can hold the position for longer than 240 s [9,15,46], and Jorgenssen and Nicolaisen suggested that the test should be continued beyond this time [46]. The populations also varied across studies, from patients with prior low back pain [10,24] or current chronic low back pain [20,31,39,42] to patients with no history of low back pain [10,24,34,35] or 15-year-old students [47,48]. In addition, several studies failed to separate data from males and females [22,24]. As expected, these numerous methodological variations translate into considerable discrepancies in study findings (Table 1). Biering-Sorensen [9] and Holmstrom et al. [10] found high mean position-holding times, not only in healthy individuals (198 and 171.5 seconds, respectively), but also in patients with low back pain (163 and 137.5 s, respectively). Most other studies found lower values in healthy individuals [21,22,24,35,44]. 4. Predictive validity of the Sorensen test Biering-Sorensen [9] reported that a position-holding time less than 176 s predicted low back pain during the next year in males, whereas a time greater than 198 s predicted absence of low back pain. Importantly, the test had no predictive validity in females. In a study by Luoto et al. [13], separating the participants into three groups based on position-holding times showed that a time less than 58 s was associated with a threefold increase in the risk of low back pain, as compared to a time greater than 104 s. Sjolie and Ljunggren et al. [49] and Adams et al. [50] found that the Sorensen test predicted low back pain in both males and females, whereas others found no predictive value [51–54]. Mannion et al. [44] reported that the risk of low back pain was independent from the position-holding time but was correlated with muscle fatigability as measured by surface electromyography during the test. In miners, Stewart et al. [55] found no significant differences in position-holding time between individuals with and without a history of low back pain.

5. Discriminative validity of the Sorensen test In many studies, the position-holding time was significantly decreased in patients with chronic low back pain [9,11,15,22,24,39,56,57]. This finding suggests that chronic low back pain may be associated with decreased isometric endurance of the trunk extensor muscles.

6. Biometric characteristics In several studies, neither body weight [42,58] nor mass moment of the trunk [10] influenced the position-holding time. Other studies, however, found a negative correlation between body weight and position-holding time [9,19,21, 27,40]. The potential influence of age and stature remains debated [9,10,21,27]. In contrast, there is general agreement that differences exist between males and females. With a few exceptions [21,42,59], studies found significantly longer position-holding times in females [9,35,40,44,60]. Similarly, spectral analysis of electromyography signals recorded during the test indicated greater muscle fatigability in males [14,29,40,44,58]. Several hypotheses have been put forward to explain this gender-related difference. In females, the weight of the upper body is less and the center of gravity of the trunk lowers, as compared to males [9,11]. However, the position-holding time remained longer in females wearing weights attached to the upper body [61] or performing isometric trunk muscle endurance tests in the standing position [11]. The greater degree of lumbar lordosis in females may afford a mechanical advantage by lengthening the lever arm of the spinal erector muscles [62,63]. An influence of sex hormones has been suggested also [11,35]. Nevertheless, the most compelling hypothesis involves differences in muscle composition. Mannion et al. [64] suggested that the spinal muscles may show better adaptation to aerobic exercise in females as a result of a larger proportion of slow Type I fibers in the cross-sectional muscle area.

46

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

7. Reproducibility The reproducibility of the Sorensen test has been evaluated, but the studies either included small numbers of individuals [10,11,30,35,60] or used the correlation coefficient r, which is not optimal for assessing test reproducibility [10,21,34,36,38,57]. Investigations that relied on the intraclass coefficient of correlation (ICC) usually found that reproducibility was satisfactory (ICC > 0.75) [65] both in healthy individuals and in patients with low back pain. Simmonds et al. [22] reported that ICC values were 0.73, 0.68, and 0.99 for within-session, session-to-session, and intraobserver reproducibility, respectively, in healthy individuals; corresponding values in patients with low back pain were 0.91, 0.88, and 0.99. In a study of interobserver reproducibility, Latimer et al. found ICC values of 0.77, 0.83, and 0.88 in individuals with prior low back pain, no symptoms, and current low back pain, respectively [24]. Reproducibility was poorer when a Roman chair was used for the test. In a study of 12 healthy individuals conducted by Mayer et al. [34], the correlation coefficient was 0.2. Keller et al. [31] reported that the coefficient of variation was 20–21% in 31 patients with low back pain and 31 healthy individuals.

8. Validity Although Hansen [15] described the test as a tool for evaluating back strength, studies subsequently established that it assesses isometric muscle endurance. Furthermore, the muscle contractions elicited by the test were found to be no greater than 40–52% of the maximal voluntary contractile force [10,25,35,45,66,67]. Similarly, the electromyographic activity of the spinal erector muscles rarely exceeded 40% of its maximal value [67,68]. The Sorensen test has been misinterpreted as a specific tool for evaluating the back muscles [13]. Published studies demonstrate that the test assesses the endurance of all the muscles involved in extension of the trunk, which include not only the paraspinal muscles, most notably the multifidus muscle [25,69], but also the hip extensor muscles. The contribution of the gluteus maximus and hamstring muscles remains controversial [42,70,71]. Sparto et al. [72] and Arokosky et al. [69] stated that these muscles played a minor role, whereas others reported a correlation between the position-holding time and the time-course of hip extensor fatigability as assessed by surface electromyography, suggesting a significant role for the hip extensor muscles [40,42]. Another challenge to the validity of the Sorensen test comes from evidence that the position-holding time is unrelated to the cross-sectional area of the paraspinal muscles [39,73]. An influence of individual factors such as motivation, pain tolerance, and competitiveness has been suggested [66,74]. In individuals who stop the test because of pain or breathing problems [9,24,27,28,35], the result may not reflect muscle

performance. In this situation, a submaximal Sorensen test coupled with electromyography or a Borg scale evaluation might be sufficient for documenting muscle fatigability while limiting the role for individual factors such as motivation [29,35].

9. Sensitivity to change The position-holding time has been reported to increase significantly after active rehabilitation therapy [38,75]. A training program involving dynamic exercises performed on a Roman chair regularly over several weeks was followed by a significant increase in the position-holding time [71], although measurements obtained using a dedicated dynamometer showed no increase in back extensor muscle strength [32,71].

10. Spinal loads induced by the Sorensen test Callaghan et al. [76] estimated that the compression load imposed on the spine during the brief Sorensen test was 4000 N, which is slightly above the value recommended by the National Institute of Occupational Security and Health in 1981 [77]. Pain, including spinal pain, may cause the patient to discontinue the test [9,24,27,28,35]. However, no persistent adverse effects such as pain exacerbation have been reported. Simmonds et al. [22] found high within-session reproducibility and recorded no instances of lasting pain induced by the test. Measurements of the lumbar curvature with the trunk in a horizontal position showed no increase in the normal lumbar lordosis [76]. Nevertheless, the suggestion by Tsuboi et al. [14] that the test be performed with the trunk extended 5° above the horizontal seems inappropriate.

11. Variants of the Sorensen test 11.1. Dynamometric measurements Tests for evaluating isometric spinal muscle endurance using a dynamometer have been developed [11,44,78]. Jorgenssen et al. [11] reported that dynamometric measurements obtained at a fixed percentage of the voluntary maximal force (usually 50–60%) were superior over the Sorensen test with a 4-min maximum in several ways: the influence of anthropometric factors was smaller, reproducibility was better (with a correlation coefficient of 0.89 as compared to 0.82), discriminative validity was greater, and the time needed for the test was shorter, resulting in a smaller influence of motivation. However, whereas the Sorensen test requires only submaximal muscle contraction, dynamometric tests require determination of the maximal voluntary force, which may be inappropriate in some patients. Furthermore, pain may result

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

47

in underestimation of the maximal voluntary force and therefore in spurious endurance test results. 11.2. The Ito test (Fig. 4) Ito et al. [79] developed a test for evaluating isometric endurance of the trunk extensor muscles. The patient lies in the prone position with a pad under the abdomen and the arms along the sides. When a signal is given, the individual lifts the upper body while flexing the neck as much as possible and contracting the gluteus maximus muscles to stabilize the pelvis. The test consists in holding this position as long as possible (without exceeding 5 min) while breathing normally. This simple test was described by Ito et al. as inducing less lumbar lordosis than the Sorensen test. Shirado et al. [80] reported that maximum neck flexion together with pelvic stabilization resulted in maximum activity of the erector spinae muscles. In a study of 190 individuals, Ito et al. [79] found that their test discriminated between healthy controls and patients with low back pain. Evaluation of session-to-session reproducibility showed that the ICC was 0.97 in healthy controls and 0.93 in low-back-pain patients [79]. The Ito test does not seem to induce pain and may result in less spinal loading than the Sorensen test. Furthermore, as the lower body is not fixed, the contribution of the hip extensor muscles may be smaller [68]. Factors that limit international recognition of the Ito test include the absence of studies, the absence of a standardized test procedure (type of pad, extent of upper-body lifting, etc.), and the theoretical risk of exaggerating the degree of lumbar lordosis. 11.3. McIntosh tests Moreau et al. [81] noted that two other tests have been described in the literature, for evaluating the isometric endurance of the upper and lower spinal extensor muscles, respectively. However, the only published study of these tests [82] fails to provide information on validity, safety, and potential use in low-back-pain patients. 11.4. Dynamic evaluations Repetitive arch-up tests provide a dynamic evaluation of the trunk extensor muscles without requiring the use of a dynamometer [21,59,83–86]. The position is derived from the Sorensen test. The test consists in flexing the trunk at 45° then returning to the horizontal position as many times as possible, at a rate of one arch-up every 2–3 s. Moreland et al. [28] used a test in which the lower limbs were fixed to a triangular pad and the patient was asked to

Fig. 4. The Ito test [79].

Fig. 5. Moreland et al.’s [28] dynamic test for evaluating the trunk extensor muscles.

flex the trunk so as to touch the table with the nose then to return to the horizontal position at a rate of 25 arch-ups per minute (Fig. 5). In a study by Uderman et al. [87], the test was done on a Roman chair and the patients asked to arch up repeatedly over a 90° angle. Whereas the static version of the Sorensen test has been widely used in published studies, the dynamic variant has received less attention. Available data suggest that results may be similar in males and females [61] and that the discriminative validity may be decreased as compared to the static test [21,59]. As with the static test, the occurrence of pain or cramps may limit the validity of the test [28,83]. In addition, the contribution of the hip extensor muscles increases gradually from one repetition to the next, further limiting the validity of the test [88,89]. Thus, in-depth studies are needed to evaluate the usefulness and limitations of these dynamic tests.

12. Conclusions The Sorensen test allows for a rapid, simple, and reproducible evaluation of the isometric endurance of the trunk extensor muscles. It discriminates between healthy individuals and patients with low back pain and may predict the occurrence of low back pain in the near future. Although the Sorensen test has been extensively studied, the better performance among females remains partly unexplained and the contribution of the hip extensor muscles is unknown. The absence of a single standardized test procedure is an impediment to comparative studies. The role for motivation, the fact that pain can lead patients to stop the test, and the impossibility of quantifying the relative muscle strength developed by the individual constitute the major shortcomings of the Sorensen test. Nevertheless, data in the literature argue in favor of the Sorensen test for evaluating the isometric endurance of the trunk extensor muscles. The Ito test and the dynamic variants of the Sorensen test need to be investigated further.

48

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

References [1]

[2]

[3]

[4] [5]

[6]

[7]

[8]

[9] [10]

[11] [12]

[13]

[14]

[15]

[16]

[17]

[18]

[19]

Hillman M, Wright A, Rajaratnam G, Tennant A, Chamberlain MA. Prevalence of low back pain in the community: implications for service provision in Bradford, UK. J Epidemiol Community Health 1996;50:347–52. Leboeuf-Yde C, Klougart N, Lauritzen T. How common is low back pain in the Nordic population? Data from a recent study on a middleaged general Danish population and four surveys previously conducted in the Nordic countries. Spine 1996;21:1518–26. Papageorgiou AC, Croft PR, Ferry S, Jayson MI, Silman AJ. Estimating the prevalence of low back pain in the general population. Evidence from the South Manchester Back Pain Survey. Spine 1995;20: 1889–94. Andersson GB, Svensson HO, Oden A. The intensity of work recovery in low back pain. Spine 1983;8:880–4. Frank JW, Brooker AS, DeMaio SE, Kerr MS, Maetzel A, Shannon HS, et al. Disability resulting from occupational low back pain. Part II: What do we know about secondary prevention? A review of the scientific evidence on prevention after disability begins. Spine 1996; 21:2918–29. Mayer TG, Gatchel RJ, Kishino N, Keeley J, Capra PN, Mayer H, et al. Objective assessment of spine function following industrial injury. A prospective study with comparison group and one-year follow-up. Spine 1985;10:482–93. Bendix AE, Bendix T, Haestrup C, Busch E. A prospective, randomized 5-year follow-up study of functional restoration in chronic low back pain patients. Eur Spine J 1998;7:111–9. Van Tulder M, Malmivaara A, Esmail R, Koes B. Exercise therapy for low back pain: a systematic review within the framework of the Cochrane collaboration back review group. Spine 2000;25:2784–96. Biering-Sorensen F. Physical measurements as risk indicators for low-back trouble over a one-year period. Spine 1984;9:106–19. Hölmstrom E, Moritz U, Andersson M. Trunk muscle strength and back muscle endurance in construction workers with and without low back disorders. Scand J Rehabil Med 1992;24:3–10. Jorgensen K. Human trunk extensor muscles physiology and ergonomics. Acta Physiol Scand Suppl 1997;637:1–58. Kujala UM, Taimela S, Viljanen T, Jutila H, Viitasalo JT, Videman T, et al. Physical loading and performance as predictors of back pain in healthy adults. A 5-year prospective study. Eur J Appl Physiol Occup Physiol 1996;73:452–8. Luoto S, Heliovaara M, Hurri H, Alaranta H. Static back endurance and the risk of low-back pain. Clin Biomech (Bristol, Avon) 1995;10: 323–4. Tsuboi T, Satou T, Egawa K, Izumi Y, Miyazaki M. Spectral analysis of electromyogram in lumbar muscles: fatigue induced endurance contraction. Eur J Appl Physiol Occup Physiol 1994;69:361–6. Hansen JW. Postoperative management in lumbar disc protrusions. I. Indications, method and results. II. Follow-up on a trained and an untrained group of patients. Acta Orthop Scand 1964;17(Suppl 71):1– 47. Troup JD, Chapman AE. Changes in the waveform of the electromyogram during fatiguing activity in the muscles of the spine and hips: the analysis of postural stress. Electromyogr Clin Neurophysiol 1972;12: 347–65. Mannion AF, Dumas GA, Stevenson JM, Cooper RG. The influence of muscle fiber size and type distribution on electromyographic measures of back muscle fatigability. Spine 1998;23:576–84. Ng JK, Richardson CA. Reliability of electromyographic power spectral analysis of back muscle endurance in healthy subjects. Arch Phys Med Rehabil 1996;77:259–64. Gibbons LE, Videman T, Battie MC. Determinants of isokinetic and psychophysical lifting strength and static back muscle endurance: a study of male monozygotic twins. Spine 1997;22:2983–90.

[20] Suter E, Lindsay D. Back muscle fatigability is associated with knee extensor inhibition in subjects with low back pain. Spine 2001;26: E361–E366. [21] Alaranta H, Hurri H, Heliovaara M, Soukka A, Harju R. Nondynamometric trunk performance tests: reliability and normative data. Scand J Rehabil Med 1994;26:211–5. [22] Simmonds MJ, Olson SL, Jones S, Hussein T, Lee CE, Novy D, et al. Psychometric characteristics and clinical usefulness of physical performance tests in patients with low back pain. Spine 1998;23:2412– 21. [23] Mayer JM, Graves JE, Robertson VL, Pierra EA, Verna JL, PloutzSnyder LL. Electromyographic activity of the lumbar extensor muscles: effect of angle and hand position during Roman chair exercise. Arch Phys Med Rehabil 1999;80:751–5. [24] Latimer J, Maher CG, Refshauge K, Colaco I. The reliability and validity of the Biering-Sorensen test in asymptomatic subjects and subjects reporting current or previous nonspecific low back pain. Spine 1999;24:2085–90. [25] Ng JK, Richardson CA, Jull GA. Electromyographic amplitude and frequency changes in the iliocostalis lumborum and multifidus muscles during a trunk holding test. Phys Ther 1997;77:954–61. [26] Cooper RG, Stokes MJ, Sweet C, Taylor RJ, Jayson MI. Increased central drive during fatiguing contractions of the paraspinal muscles in patients with chronic low back pain. Spine 1993;18:610–6. [27] Latikka P, Battie MC, Videman T, Gibbons LE. Correlations of isokinetic and psychophysical back lift and static back extensor endurance tests in men. Clin Biomech (Bristol, Avon) 1995;10:325–30. [28] Moreland J, Finch E, Stratford P, Balsor B, Gill C. Interrater reliability of six tests of trunk muscle function and endurance. J Orthop Sports Phys Ther 1997;26:200–8. [29] Dedering A, Nemeth G, Harms-Ringdahl K. Correlation between electromyographic spectral changes and subjective assessment of lumbar muscle fatigue in subjects without pain from the lower back. Clin Biomech (Bristol, Avon) 1999;14:103–11. [30] Dedering A. Roos af Hjelmsater M, Elfving B, Harms-Ringdahl K, Nemeth G. Between-days reliability of subjective and objective assessments of back extensor muscle fatigue in subjects without lower-back pain. J Electromyogr Kinesiol 2000;10:151–8. [31] Keller A, Hellesnes J, Brox JI. Reliability of the isokinetic trunk extensor test, Biering-Sorensen test, and Astrand bicycle test: assessment of intraclass correlation coefficient and critical difference in patients with chronic low back pain and healthy individuals. Spine 2001;26:771–7. [32] Mayer JM, Udermann BE, Graves JE, Ploutz-Snyder LL. Effect of Roman chair exercise training on the development of lumbar extension strength. J Strength Cond Res 2003;17:356–61. [33] Mayer JM, Verna JL, Manini TM, Mooney V, Graves JE. Electromyographic activity of the trunk extensor muscles: effect of varying hip position and lumbar posture during Roman chair exercise. Arch Phys Med Rehabil 2002;83:1543–6. [34] Mayer T, Gatchel R, Betancur J, Bovasso E. Trunk muscle endurance measurement. Isometric contrasted to isokinetic testing in normal subjects. Spine 1995;20:920–7. [35] Mannion AF, Dolan P. Electromyographic median frequency changes during isometric contraction of the back extensors to fatigue. Spine 1994;19:1223–9. [36] Hyytiainen K, Salminen JJ, Suvitie T, Wickstrom G, Pentti J. Reproducibility of nine tests to measure spinal mobility and trunk muscle strength. Scand J Rehabil Med 1991;23:3–10. [37] Chok B, Lee R, Latimer J, Tan SB. Endurance training of the trunk extensor muscles in people with subacute low back pain. Phys Ther 1999;79:1032–42. [38] Moffroid MT, Haugh LD, Haig AJ, Henry SM, Pope MH. Endurance training of trunk extensor muscles. Phys Ther 1993;73:10–7. [39] Hultman G, Nordin M, Saraste H, Ohlsen H. Body composition, endurance, strength, cross-sectional area, and density of MM erector spinae in men with and without low back pain. J Spinal Disord 1993;6:114–23.

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50 [40] Kankaanpaa M, Laaksonen D, Taimela S, Kokko SM, Airaksinen O, Hanninen O. Age, sex, and body mass index as determinants of back and hip extensor fatigue in the isometric Sorensen back endurance test. Arch Phys Med Rehabil 1998;79:1069–75. [41] Koumantakis GA, Arnall F, Cooper RG, Oldham JA. Paraspinal muscle EMG fatigue testing with two methods in healthy volunteers. Reliability in the context of clinical applications. Clin Biomech (Bristol, Avon) 2001;16:263–6. [42] Moffroid M, Reid S, Henry SM, Haugh LD, Ricamato A. Some endurance measures in persons with chronic low back pain. J Orthop Sports Phys Ther 1994;20:81–7. [43] Rashiq S, Koller M, Haykowsky M, Jamieson K. The effect of opioid analgesia on exercise test performance in chronic low back pain. Pain 2003;106:119–25. [44] Mannion AF, Connolly B, Wood K, Dolan P. The use of surface EMG power spectral analysis in the evaluation of back muscle function. J Rehabil Res Dev 1997;34:427–39. [45] Smidt GL, Blanpied PR. Analysis of strength tests and resistive exercises commonly used for low-back disorders. Spine 1987;12: 1025–34. [46] Jorgensen K, Nicolaisen T. Two methods for determining trunk extensor endurance. A comparative study. Eur J Appl Physiol Occup Physiol 1986;55:639–44. [47] Salminen JJ, Erkintalo-Tertti MO, Paajanen HE. Magnetic resonance imaging findings of lumbar spine in the young: correlation with leisure time physical activity, spinal mobility, and trunk muscle strength in 15-year-old pupils with or without low-back pain. J Spinal Disord 1993;6:386–91. [48] Salminen JJ, Oksanen A, Maki P, Pentti J, Kujala UM. Leisure time physical activity in the young. Correlation with low-back pain, spinal mobility and trunk muscle strength in 15-year-old school children. Int J Sports Med 1993;14:406–10. [49] Sjolie AN, Ljunggren AE. The significance of high lumbar mobility and low lumbar strength for current and future low back pain in adolescents. Spine 2001;26:2629–36. [50] Adams MA, Mannion AF, Dolan P. Personal risk factors for first-time low back pain. Spine 1999;24:2497–505. [51] Gibbons LE, Videman T, Battie MC. Isokinetic and psychophysical lifting strength, static back muscle endurance, and magnetic resonance imaging of the paraspinal muscles as predictors of low back pain in men. Scand J Rehabil Med 1997;29:187–91. [52] Klaber Moffett JA, Hughes GI, Griffiths P. A longitudinal study of low back pain in student nurses. Int J Nurs Stud 1993;30:197–12. [53] Salminen JJ, Erkintalo M, Laine M, Pentti J. Low back pain in the young. A prospective three-year follow-up study of subjects with and without low back pain. Spine 1995;20:2101–7 [discussion 2108]. [54] Takala EP, Viikari-Juntura E. Do functional tests predict low back pain? Spine 2000;25:2126–32. [55] Stewart M, Latimer J, Jamieson M. Back extensor muscle endurance test scores in coal miners in Australia. J Occup Rehabil 2003;13:79– 89. [56] Novy DM, Simmonds MJ, Olson SL, Lee CE, Jones SC. Physical performance: differences in men and women with and without low back pain. Arch Phys Med Rehabil 1999;80:195–8. [57] Salminen JJ, Maki P, Oksanen A, Pentti J. Spinal mobility and trunk muscle strength in 15-year-old schoolchildren with and without lowback pain. Spine 1992;17:405–11. [58] Umezu Y, Kawazu T, Tajima F, Ogata H. Spectral electromyographic fatigue analysis of back muscles in healthy adult women compared with men. Arch Phys Med Rehabil 1998;79:536–8. [59] Gronblad M, Hurri H, Kouri JP. Relationships between spinal mobility, physical performance tests, pain intensity and disability assessments in chronic low back pain patients. Scand J Rehabil Med 1997; 29:17–24. [60] McGill SM, Childs A, Liebenson C. Endurance times for low back stabilization exercises: clinical targets for testing and training from a normal database. Arch Phys Med Rehabil 1999;80:941–4.

49

[61] Clark BC, Manini TM. The DJ, Doldo NA, Ploutz-Snyder LL. Gender differences in skeletal muscle fatigability are related to contraction type and EMG spectral compression. J Appl Physiol 2003;94:2263– 72. [62] Macintosh JE, Bogduk N, Pearcy MJ. The effects of flexion on the geometry and actions of the lumbar erector spinae. Spine 1993;18: 884–93. [63] Tveit P, Daggfeldt K, Hetland S, Thorstensson A. Erector spinae lever arm length variations with changes in spinal curvature. Spine 1994; 19:199–204. [64] Mannion AF, Dumas GA, Cooper RG, Espinosa FJ, Faris MW, Stevenson JM. Muscle fibre size and type distribution in thoracic and lumbar regions of erector spinae in healthy subjects without low back pain: normal values and sex differences. J Anat 1997;190:505–13. [65] Lee D, Koh D, Ong CN. Statistical evaluation of agreement between two methods for measuring a quantitative variable. Comput Biol Med 1989;19:61–70. [66] Moffroid MT. Endurance of trunk muscles in persons with chronic low back pain: assessment, performance, training. J Rehabil Res Dev 1997;34:440–7. [67] Plamondon A, Marceau C, Stainton S, Desjardins P. Toward a better prescription of the prone back extension exercise to strengthen the back muscles. Scand J Med Sci Sports 1999;9:226–32. [68] Plamondon A, Serresse O, Boyd K, Ladouceur D, Desjardins P. Estimated moments at L5/S1 level and muscular activation of back extensors for six prone back extension exercises in healthy individuals. Scand J Med Sci Sports 2002;12:81–9. [69] Arokoski JP, Kankaapaa M, Valta T, Juvonen I, Partanen J, Taimela S, et al. Back and hip extensor muscle function during therapeutic exercises. Arch Phys Med Rehabil 1999;80:842–50. [70] Plamondon A, Trimble K, Larivière C, Desjardins P. Back muscle fatigue during intermittent prone back extension exercise. Scand J Med Sci Sports 2004;14:1–0. [71] Verna JL, Mayer JM, Mooney V, Pierra EA, Robertson VL, Graves JE. Back extension endurance and strength: the effect of variable-angle roman chair exercise training. Spine 2002;27:1772–7. [72] Sparto PJ, Parnianpour M, Reinsel TE, Simon S. Spectral and temporal responses of trunk extensor electromyography to an isometric endurance test. Spine 1997;22:418–26. [73] Gibbons LE, Latikka P, Videman T, Manninen H, Battie MC. The association of trunk muscle cross-sectional area and magnetic resonance image parameters with isokinetic and psychophysical lifting strength and static back muscle endurance in men. J Spinal Disord 1997;10:398–403. [74] Mannion AF, Dolan P, Adams MA. Psychological questionnaires: do “abnormal” scores precede or follow first-time low back pain? Spine 1996;21:2603–11. [75] Mannion AF, Taimela S, Muntener M, Dvorak J. Active therapy for chronic low back pain part 1. Effects on back muscle activation, fatigability, and strength. Spine 2001;26:897–908. [76] Callaghan JP, Gunning JL, McGill SM. The relationship between lumbar spine load and muscle activity during extensor exercises. Phys Ther 1998;78:8–18. [77] NIOSH. National Institute for Occupational Safety and Health (USA). Guidelines for lifting. 1981. [78] Nicolaisen T, Jorgensen K. Trunk strength, back muscle endurance and low-back trouble. Scand J Rehabil Med 1985;17:121–7. [79] Ito T, Shirado O, Suzuki H, Takahashi M, Kaneda K, Strax TE. Lumbar trunk muscle endurance testing: an inexpensive alternative to a machine for evaluation. Arch Phys Med Rehabil 1996;77:75–9. [80] Shirado O, Ito T, Kaneda K, Strax TE. Electromyographic analysis of four techniques for isometric trunk muscle exercises. Arch Phys Med Rehabil 1995;76:225–9. [81] Moreau CE, Green BN, Johnson CD, Moreau SR. Isometric back extension endurance tests: a review of the literature. J Manipulative Physiol Ther 2001;24:110–22.

50

C. Demoulin et al. / Joint Bone Spine 73 (2006) 43–50

[82] McIntosh G, Wilson L, Affieck M, Hall H. Trunk and lower extremity muscle endurance: normative data for adults. J Rehabil Outcome Meas 1998;2:20–39. [83] Kuukkanen T, Malkia E. Muscular performance after a 3 month progressive physical exercise program and 9 month follow-up in subjects with low back pain. A controlled study. Scand J Med Sci Sports 1996;6:112–21. [84] Leino P, Aro S, Hasan J. Trunk muscle function and low back disorders: a ten-year follow-up study. J Chronic Dis 1987;40:289–96. [85] Rissanen A, Alaranta H, Sainio P, Harkonen H. Isokinetic and nondynamometric tests in low back pain patients related to pain and disability index. Spine 1994;19:1963–7.

[86] Rissanen A, Heliovaara M, Alaranta H, Taimela S, Malkia E, Knekt P, et al. Does good trunk extensor performance protect against backrelated work disability? J Rehabil Med 2002;34:62–6. [87] Udermann BE, Mayer JM, Graves JE, Murray SR. Quantitative assessment of lumbar paraspinal muscle endurance. J Athl Train 2003;38:259–62. [88] Clark BC, Manini TM, Mayer JM, Ploutz-Snyder LL, Graves JE. Electromyographic activity of the lumbar and hip extensors during dynamic trunk extension exercise. Arch Phys Med Rehabil 2002;83: 1547–52. [89] Clark BC, Manini TM, Ploutz-Snyder LL. Derecruitment of the lumbar musculature with fatiguing trunk extension exercise. Spine 2003;28:282–7.