Isolated Lumbar Extension Resistance Training Improves Strength, Pain, and Disability, but Not Spinal Height or Shrinkage ("Creep") in Participants with Chronic Low Back Pain.

Objective. Loss of disc height is commonly associated with chronic low back pain (CLBP). Isolated lumbar extension (ILEX) exercise for the lumbar extensors is recommended to treat CLBP and is suggested such exercise might promote disc healing and regeneration. This study examined a 12-week ILEX intervention on indirect determination of disc height and shrinkage through seated stadiometry, strength, pain, and disability. Design. A quasi-experimental wait-list controlled design was used. Nine participants underwent pretesting (T1), a 12-week control period, retesting (T2), a 12-week intervention period, and finally posttesting (T3). Seated stadiometry, ILEX strength, pain, and disability were measured at each time point. Results. No significant repeated-measures effects for any seated stadiometry variables occurred. Significant improvement across the intervention period (T2 to T3) was found for strength (P <0.0001; effect size [ES] = 2.42). Change in pain was not significant for repeated effects (P = 0.064); however, ES for the intervention period (T2 to T3) was moderate (ES = -0.77). Change in disability was significant between time point T1 and T3 (P = 0.037) and ES for the intervention period (T2 to T3) was large (ES = -0.92). Pain and disability achieved minimal clinically important changes. Conclusions. This is apparently the first study to examine disc change in vivo after exercise in CLBP. Results of the present study, though supporting ILEX resistance training to improve strength, pain, and disability, did not find any effect on spinal height.

A Comparison of Isolated Lumbar Extension Strength Between Healthy Asymptomatic Participants and Chronic Low Back Pain Participants Without Previous Lumbar Spine Surgery.

STUDY DESIGN: Cross-sectional case-control study. OBJECTIVE: To compare isolated lumbar extension strength between healthy asymptomatic participants and participants with chronic low back pain (CLBP), while controlling for previous lumbar spine surgery. SUMMARY OF BACKGROUND DATA: Deconditioning of the lumbar musculature is common in those with previous lumbar surgery, resulting in decreased strength and endurance. Evidence is required to support whether this is the case for participants with CLBP yet no previous surgery compared with asymptomatic participants. METHODS: Forty-two healthy (25 males and 17 females) asymptomatic participants, and 53 participants with non-specific CLBP (30 males and 23 females) aged between 19 and 76 years were recruited. Maximal isometric isolated lumbar extension (ILEX) strength was examined. RESULTS: A Mann-Whitney U test indicated that ILEX strength was significantly greater in the asymptomatic group compared with the CLBP group (Z = 1441.00, P = 0.014). Post-hoc effect size was calculated to be d = 0.56, showing a moderate effect. CONCLUSION: These results indicate that ILEX weakness and lumbar extensor deconditioning is present independent of surgery and may be a factor involved in CLBP. As such, lumbar extensor deconditioning would appear to be a reasonable target for interventions in CLBP. LEVEL OF EVIDENCE: 3.

The relationship between balance performance, lumbar extension strength, trunk extension endurance, and pain in participants with chronic low back pain, and those without.

BACKGROUND: Chronic low back pain is associated with lumbar extensor deconditioning. This may contribute to decreased neuromuscular control and balance. However, balance is also influenced by the hip musculature. Thus, the purpose of this study was to examine balance in both asymptomatic participants and those with chronic low back pain, and to examine the relationships among balance, lumbar extension strength, trunk extension endurance, and pain. METHODS: Forty three asymptomatic participants and 21 participants with non-specific chronic low back pain underwent balance testing using the Star Excursion Balance Test, lumbar extension strength, trunk extension endurance, and pain using a visual analogue scale. FINDINGS: Significant correlations were found between lumbar extension strength and Star Excursion Balance Test scores in the chronic low back pain group (r = 0.439-0.615) and in the asymptomatic group (r = 0.309-0.411). Correlations in the chronic low back pain group were consistently found in posterior directions. Lumbar extension strength explained ~19.3% to ~37.8% of the variance in Star Excursion Balance Test scores for the chronic low back pain group and ~9.5% to ~16.9% for the asymptomatic group. INTERPRETATION: These results suggest that the lumbar extensors may be an important factor in determining the motor control dysfunctions, such as limited balance, that arise in chronic low back pain. As such, specific strengthening of this musculature may be an approach to aid in reversing these dysfunctions.

Variability in Strength, Pain, and Disability Changes in Response to an Isolated Lumbar Extension Resistance Training Intervention in Participants with Chronic Low Back Pain.

Strengthening the lumbar extensor musculature is a common recommendation for chronic low back pain (CLBP). Although reported as effective, variability in response in CLBP populations is not well investigated. This study investigated variability in responsiveness to isolated lumbar extension (ILEX) resistance training in CLBP participants by retrospective analysis of three previous randomized controlled trials. Data from 77 participants were available for the intervention arms (males = 43, females = 34) 37 participants data (males = 20, females = 17) from the control arms. Intervention participants had all undergone 12 weeks of ILEX resistance training and changes in ILEX strength, pain (visual analogue scale; VAS), and disability (Oswestry disability index; ODI) measured. True inter-individual (i.e., between participants) variability in response was examined through calculation of difference in the standard deviation of change scores for both control and intervention arms. Intervention participants were classified into responder status using k-means cluster analysis for ILEX strength changes and using minimal clinically important change cut-offs for VAS and ODI. Change in average ILEX strength ranged 7.6 Nm (1.9%) to 192.1 Nm (335.7%). Change in peak ILEX strength ranged -12.2 Nm (-17.5%) to 276.6 Nm (169.6%). Participants were classified for strength changes as low (n = 31), medium (n = 36), and high responders (n = 10). Change in VAS ranged 12.0 mm to -84.0 mm. Participants were classified for VAS changes as negative (n = 3), non-responders (n = 34), responders (n = 15), and high responders (n = 19). Change in ODI ranged 18 pts to -45 pts. Participants were classified for ODI changes as negative (n = 2), non-responders (n = 21), responders (n = 29), and high responders (n = 25). Considerable variation exists in response to ILEX resistance training in CLBP. Clinicians should be aware of this and future work should identify factors prognostic of successful outcomes.

Associations between Trunk Extension Endurance and Isolated Lumbar Extension Strength in Both Asymptomatic Participants and Those with Chronic Low Back Pain.

BACKGROUND: Strength and endurance tests are important for both clinical practice and research due to the key role they play in musculoskeletal function. In particular, deconditioning of the lumbar extensor musculature has been associated with low back pain (LBP). Due to the relationship between strength and absolute endurance, it is possible that trunk extension (TEX) endurance tests could provide a proxy measure of isolated lumbar extension (ILEX) strength and thus represent a simple, practical alternative to ILEX measurements. Though, the comparability of TEX endurance and ILEX strength is presently unclear and so the aim of the present study was to examine this relationship. METHODS: Thirty eight healthy participants and nineteen participants with non-specific chronic LBP and no previous lumbar surgery participated in this cross-sectional study design. TEX endurance was measured using the Biering-Sorensen test. A maximal ILEX strength test was performed on the MedX lumbar-extension machine. RESULTS: A Pearson's correlation revealed no relationship between TEX endurance and ILEX strength in the combined group (r = 0.035, p = 0.793), the chronic LBP group (r = 0.120, p = 0.623) or the asymptomatic group (r = -0.060, p = 0.720). CONCLUSIONS: The results suggest that TEX is not a good indicator of ILEX and cannot be used to infer results regarding ILEX strength. However, a combination of TEX and ILEX interpreted together likely offers the greatest and most comprehensive information regarding lumbo-pelvic function during extension.

Determining the reliability of a custom built seated stadiometry set-up for measuring spinal height in participants with chronic low back pain.

Indirect measurement of disc hydration can be obtained through measures of spinal height using stadiometry. However, specialised stadiometers for this are often custom-built and expensive. Generic wall-mounted stadiometers alternatively are common in clinics and laboratories. This study examined the reliability of a custom set-up utilising a wall-mounted stadiometer for measurement of spinal height using custom built wall mounted postural rods. Twelve participants with non-specific chronic low back pain (CLBP; females n = 5, males n = 7) underwent measurement of spinal height on three separate consecutive days at the same time of day where 10 measurements were taken at 20 s intervals. Comparisons were made using repeated measures analysis of variance for 'trial' and 'gender'. There were no significant effects by trial or interaction effects of trial x gender. Intra-individual absolute standard error of measurement (SEM) was calculated for spinal height using the first of the 10 measures, the average of 10 measures, the total shrinkage, and the rate of shrinkage across the 10 measures examined as the slope of the curve when a linear regression was fitted. SEMs were 3.1 mm, 2.8 mm, 2.6 mm and 0.212, respectively. Absence of significant differences between trials and the reported SEMs suggests this custom set-up for measuring spinal height changes is suitable use as an outcome measure in either research or clinical practice in participants with CLBP.

A Randomized Controlled Trial of the Effects of Isolated Lumbar Extension Exercise on Lumbar Kinematic Pattern Variability During Gait in Chronic Low Back Pain.

BACKGROUND: Chronic low back pain (CLBP) is a multifactorial condition with a variety of symptoms, one of which is abnormal gait. The lumbar spine and its musculature are important in controlling gait, and in CLBP the lumbar extensors are often deconditioned. Because of this specific isolated lumbar extension, exercise often is recommended. It was therefore of interest to examine its effects of upon gait variability. OBJECTIVE: To examine the effects of isolated lumbar extension resistance training on lumbar kinematic variability during gait in participants with CLBP. DESIGN: Randomized controlled trial. SETTING: University Health, Exercise and Sport Science Laboratory. PARTICIPANTS: Twenty-four participants with nonspecific CLBP. INTERVENTIONS: Participants were randomly allocated to a 12-week isolated lumbar extension exercise intervention (1×/week performing a single set to momentary muscular failure using a load equal to 80% max tested torque) or nontraining control period. MAIN OUTCOME MEASUREMENTS: Lumbar kinematics during gait, including angular displacement, kinematic waveform pattern (CVp), and offset (CVo) variability, were examined via 3-dimensional analyses. RESULTS: No significant changes in displacement or CVo were found as a result of the intervention; however, a small but significant reduction in sagittal plane CVp (-20.90 ± 3.53%, effect size = 0.48, P = .044) occurred, indicating improved motor pattern replication through this movement plane. CONCLUSIONS: Considering the role of the lumbar extensors in gait, and their common deconditioning in CLBP, an isolated lumbar extension resistance exercise intervention may reduce gait variability. These results suggest isolated lumbar extension exercise may specifically reduce sagittal plane variability, indicating improved motor pattern replication through this movement plane, perhaps attributable to the plane of movement used during the exercise.

Attainment rate as a surrogate indicator of the intervertebral neutral zone length in lateral bending: an in vitro proof of concept study.

BACKGROUND: Lumbar segmental instability is often considered to be a cause of chronic low back pain. However, defining its measurement has been largely limited to laboratory studies. These have characterised segmental stability as the intrinsic resistance of spine specimens to initial bending moments by quantifying the dynamic neutral zone. However these measurements have been impossible to obtain in vivo without invasive procedures, preventing the assessment of intervertebral stability in patients. Quantitative fluoroscopy (QF), measures the initial velocity of the attainment of intervertebral rotational motion in patients, which may to some extent be representative of the dynamic neutral zone. This study sought to explore the possible relationship between the dynamic neutral zone and intervertebral rotational attainment rate as measured with (QF) in an in vitro preparation. The purpose was to find out if further work into this concept is worth pursuing. METHOD: This study used passive recumbent QF in a multi-segmental porcine model. This assessed the intrinsic intervertebral responses to a minimal coronal plane bending moment as measured with a digital force guage. Bending moments about each intervertebral joint were calculated and correlated with the rate at which global motion was attained at each intervertebral segment in the first 10° of global motion where the intervertebral joint was rotating. RESULTS: Unlike previous studies of single segment specimens, a neutral zone was found to exist during lateral bending. The initial attainment rates for left and right lateral flexion were comparable to previously published in vivo values for healthy controls. Substantial and highly significant levels of correlation between initial attainment rate and neutral zone were found for left (Rho = 0.75, P = 0.0002) and combined left-right bending (Rho = 0.72, P = 0.0001) and moderate ones for right alone (Rho = 0.55, P = 0.0012). CONCLUSIONS: This study found good correlation between the initial intervertebral attainment rate and the dynamic neutral zone, thereby opening the possibility to detect segmental instability from clinical studies. However the results must be treated with caution. Further studies with multiple specimens and adding sagittal plane motion are warranted.

Can specific loading through exercise impart healing or regeneration of the intervertebral disc?

BACKGROUND CONTEXT: Low back pain (LBP) is highly prevalent and presents an enormous cost both through direct health care and indirectly through significant work and production loss. Low back pain is acknowledged widely to be a multifactorial pathology with a variety of symptoms, dysfunctions, and a number of possible sources of pain. One source that has been suspected and evidenced for some time is the intervertebral disc. Some degree of disc degeneration is a physiologic process associated with aging, however, more severe degeneration and/or structural abnormality may be indicative of a pathologic process or injury and is more commonly present in those suffering from LBP. Much like other tissues (ie, muscle, bone, etc.), it has been suspected that there exists an optimal loading strategy to promote the health of the disc. Exercise is often prescribed for LBP and effectively reduces pain and disability. However, whether specific loading through exercise might plausibly heal or regenerate the intervertebral discs is unknown. PURPOSE: To examine the effects of loading on regenerative processes in the intervertebral disc and consider the potential for specific exercise to apply loading to the lumbar spine to produce these effects. STUDY DESIGN: A brief narrative literature review. METHODS: Studies examining the effects of loading on the intervertebral discs were reviewed to examine the plausibility of using loading through exercise to induce regeneration or healing of the intervertebral disc. RESULTS: Research from animal model studies suggests the existence of a dose-response relationship between loading and regenerative processes. Although high loading at high volumes and frequencies might accelerate degeneration or produce disc injury, high loading, yet of low volume and at low frequency appears to induce potentially regenerative mechanisms, including improvements in disc proteoglycan content, matrix gene expression, rate of cell apoptosis, and improved fluid flow and solute transport. CONCLUSIONS: Research suggests a dose-response relationship between loading and disc regenerative processes and that the loading pattern typically used in the lumbar extension resistance exercise interventions (high load, low volume, and low frequency) might impart healing or regeneration of the intervertebral discs. Future research should examine an exercise intervention with in vivo measurement of changes in disc condition. This may provide further evidence for the "black box" of treatment mechanisms associated with exercise interventions.

Lumbar kinematic variability during gait in chronic low back pain and associations with pain, disability and isolated lumbar extension strength.

BACKGROUND: Chronic low back pain is a multifactorial condition with many dysfunctions including gait variability. The lumbar spine and its musculature are involved during gait and in chronic low back pain the lumbar extensors are often deconditioned. It was therefore of interest to examine relationships between lumbar kinematic variability during gait, with pain, disability and isolated lumbar extension strength in participants with chronic low back pain. METHODS: Twenty four participants with chronic low back pain were assessed for lumbar kinematics during gait, isolated lumbar extension strength, pain, and disability. Angular displacement and kinematic waveform pattern and offset variability were examined. FINDINGS: Angular displacement and kinematic waveform pattern and offset variability differed across movement planes; displacement was highest and similar in frontal and transverse planes, and pattern variability and offset variability higher in the sagittal plane compared to frontal and transverse planes which were similar. Spearman's correlations showed significant correlations between transverse plane pattern variability and isolated lumbar extension strength (r=-.411) and disability (r=.401). However, pain was not correlated with pattern variability in any plane. The r(2) values suggested 80.5% to 86.3% of variance was accounted for by other variables. INTERPRETATION: Considering the lumbar extensors role in gait, the relationship between both isolated lumbar extension strength and disability with transverse plane pattern variability suggests that gait variability may result in consequence of lumbar extensor deconditioning or disability accompanying chronic low back pain. However, further study should examine the temporality of these relationships and other variables might account for the unexplained variance.

A randomized controlled trial of limited range of motion lumbar extension exercise in chronic low back pain.

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: To compare the effects of full range of motion (ROM) and limited ROM isolated lumbar extension exercise upon full ROM lumbar extension strength, ROM, perceived pain, and disability. SUMMARY OF BACKGROUND DATA: Limited ROM is common in chronic low back pain as is lumbar extensor deconditioning. Limited ROM exercise is a common prescription but is yet to be empirically tested. METHODS: Males (n = 21) and females (n = 17) with nonspecific chronic low back pain were initially recruited. Participants were randomized to either a full ROM (FullROM) or limited ROM (LimROM) training group or a control group. A total of 24 participants (males: n = 14, females: n = 10) completed the study and were included in analysis. The intervention lasted 12 weeks. FullROM and LimROM groups completed isolated lumbar extension resistance training once per week, performing one set of exercise at 80% of their maximal tested functional torque to failure. FullROM group trained through a full ROM. LimROM group trained through the mid 50% of their full ROM.Full ROM isolated lumbar extension strength, lumbar and standing ROM (Schobers test), perceived pain (visual analogue scale), and disability (Revised Oswestry Disability Index) were measured pre- and postintervention. RESULTS: FullROM and LimROM significantly improved in full ROM lumbar extension strength, perceived pain, and disability compared with the control group. No changes occurred in lumbar or standing ROM. No significant differences were found between either FullROM or LimROM for any outcome measure. Changes in perceived pain and disability met minimal clinically important change values for FullROM (visual analogue scale, -30.3 + 25.76 mm and Oswestry Disability Index, -18.2 + 6.63 patients) and LimROM (visual analogue scale, -16.29 + 10.97 mm and Oswestry Disability Index, -12 + 5.16 patients). CONCLUSION: The results suggest that both FullROM and LimROM are equally effective in increasing full ROM lumbar extension strength and producing clinically meaningful improvement in perceived pain and disability.