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

Explaining trunk strength variation and improvement following resistance training in people with chronic low back pain: clinical and performance-based outcomes analysis

A multitude of variables contribute to the variation of trunk strength in individuals with chronic low back pain (CLBP). This study investigated a range of variables to determine which variables contribute most to variation in trunk isometric strength and gains in strength following resistance training in people with CLBP. Outcome measures were recorded from 20 participants with CLBP both at baseline and following resistance training. Regression analyses were applied with the average trunk maximum voluntary isometric torque as the dependent variable. Variance in baseline trunk flexion strength (R2 = .66) was explained by demographic covariates and a measure of trunk muscle co-activation. The baseline trunk extension strength variance (R2 = .65) was explained by demographic covariates and lumbar erector spinae (LES) activity during a maximum trunk extension contraction. Demographic variables, trunk muscle co-activation, baseline trunk flexion strength, level of physical function, and pain intensity over the past week influenced the change in trunk flexion strength after training (R2 = .93). Demographic variables and LES muscle activity explained the variance in trunk extension strength at follow-up (R2 = .64). This study supports the major influence of sex, physical function and baseline strength and muscle activity, on the variation in maximum trunk strength in participants with CLBP at baseline and gains in trunk muscle strength following progressive resistance training.

Interindividual Differences in Trainability and Moderators of Cardiorespiratory Fitness, Waist Circumference, and Body Mass Responses: A Large-Scale Individual Participant Data Meta-analysis

Although many studies have assumed variability reflects variance caused by exercise training, few studies have examined whether interindividual differences in trainability are present following exercise training. The present individual participant data (IPD) meta-analysis sought to: (1) investigate the presence of interindividual differences in trainability for cardiorespiratory fitness (CRF), waist circumference, and body mass; and (2) examine the influence of exercise training and potential moderators on the probability that an individual will experience clinically important differences. The IPD meta-analysis combined data from 1879 participants from eight previously published randomized controlled trials. We implemented a Bayesian framework to: (1) test the hypothesis of interindividual differences in trainability by comparing variability in change scores between exercise and control using Bayes factors; and (2) compare posterior predictions of control and exercise across a range of moderators (baseline body mass index (BMI) and exercise duration, intensity, amount, mode, and adherence) to estimate the proportions of participants expected to exceed minimum clinically important differences (MCIDs) for all three outcomes. Bayes factors demonstrated a lack of evidence supporting a high degree of variance attributable to interindividual differences in trainability across all three outcomes. These findings indicate that interindividual variability in observed changes are likely due to measurement error and external behavioural factors, not interindividual differences in trainability. Additionally, we found that a larger proportion of exercise participants were expected to exceed MCIDs compared with controls for all three outcomes. Moderator analyses identified that larger proportions were associated with a range of factors consistent with standard exercise theory and were driven by mean changes. Practitioners should prescribe exercise interventions known to elicit large mean changes to increase the probability that individuals will experience beneficial changes in CRF, waist circumference and body mass.

Effect of stabilization exercise combined with respiratory resistance and whole body vibration on patients with lumbar instability: A randomized controlled trial

BACKGROUND

Lumbar stability exercise promotes deep muscle functions, and it is an effective intervention method for increasing proprioceptive sensation. This study aims to explore and compare the effects of lumbar stability exercise with respiratory resistance and whole body vibration on patients with lumbar instability.

METHODS

This study is a 3-group randomized control trial. Through screening tests, 48 patients with lumbar instability were selected and randomly assigned to SE group (n = 16), stabilization exercise program using respiratory resistance (SER) group (n = 16), and stabilization exercise program using respiratory resistance and whole body vibration (SERW) group (n = 16). In order to compare the effects depending on the intervention methods, quadruple visual analogue scale (QVAS), Functional Ability Roland-Morris low back pain and disability questionnaire ([RMDQ], center of pressure path length, velocity, and area), Korean version of fear-avoidance beliefs questionnaire, and Pulmonary Function were used for measurement.

RESULTS

All of the groups showed significant improvements in QVAS, RMDQ, Korean version of fear-avoidance beliefs questionnaire, and balance abilities before and after the interventions. The SER group and SERW group showed a significant difference in QVAS and RMDQ than the SE group (P < .05). In addition, balance ability showed a significant difference in SERW group (P < .05), where only the SER group showed a significant difference in pulmonary function indexes including forced vital capacity, forced expiratory volume in 1 second, maximum inspiratory pressure, and maximum expiratory pressure (P < .05).

CONCLUSION

Stabilization exercise program using respiratory resistance and whole-body vibration administered according to the purpose of intervention methods may be effective exercise programs for people with lumbar instability.

Paraspinal Muscle Health is Related to Fibrogenic, Adipogenic, and Myogenic Gene Expression in Patients with Lumbar Spine Pathology

BACKGROUND

Lumbar spine pathology is a common feature of lower back and/or lower extremity pain and is associated with observable degenerative changes in the lumbar paraspinal muscles that are associated with poor clinical prognosis. Despite the commonly observed phenotype of muscle degeneration in this patient population, its underlying molecular mechanisms are not well understood. The aim of this study was to investigate the relationships between groups of genes within the atrophic, myogenic, fibrogenic, adipogenic, and inflammatory pathways and multifidus muscle health in individuals undergoing surgery for lumbar spine pathology.

METHODS

Multifidus muscle biopsies were obtained from patients (n = 59) undergoing surgery for lumbar spine pathology to analyze 42 genes from relevant adipogenic/metabolic, atrophic, fibrogenic, inflammatory, and myogenic gene pathways using quantitative polymerase chain reaction. Multifidus muscle morphology was examined preoperatively in these patients at the level and side of biopsy using T2-weighted magnetic resonance imaging to determine whole muscle compartment area, lean muscle area, fat cross-sectional areas, and proportion of fat within the muscle compartment. These measures were used to investigate the relationships between gene expression patterns and muscle size and quality.

RESULTS

Relationships between gene expression and imaging revealed significant associations between decreased expression of adipogenic/metabolic gene (PPARD), increased expression of fibrogenic gene (COL3A1), and lower fat fraction on MRI (r = -0.346, p = 0.018, and r = 0.386, p = 0.047 respectively). Decreased expression of myogenic gene (mTOR) was related to greater lean muscle cross-sectional area (r = 0.388, p = 0.045).

CONCLUSION

Fibrogenic and adipogenic/metabolic genes were related to pre-operative muscle quality, and myogenic genes were related to pre-operative muscle size. These findings provide insight into molecular pathways associated with muscle health in the presence of lumbar spine pathology, establishing a foundation for future research that addresses how these changes impact outcomes in this patient population.

A Systematic Review Examining the Approaches Used to Estimate Interindividual Differences in Trainability and Classify Individual Responses to Exercise Training

Background: Many reports describe statistical approaches for estimating interindividual differences in trainability and classifying individuals as "responders" or "non-responders." The extent to which studies in the exercise training literature have adopted these statistical approaches remains unclear. Objectives: This systematic review primarily sought to determine the extent to which studies in the exercise training literature have adopted sound statistical approaches for examining individual responses to exercise training. We also (1) investigated the existence of interindividual differences in trainability, and (2) tested the hypothesis that less conservative thresholds inflate response rates compared with thresholds that consider error and a smallest worthwhile change (SWC)/minimum clinically important difference (MCID). Methods: We searched six databases: AMED, CINAHL, EMBASE, Medline, PubMed, and SportDiscus. Our search spanned the aerobic, resistance, and clinical or rehabilitation training literature. Studies were included if they used human participants, employed standardized and supervised exercise training, and either: (1) stated that their exercise training intervention resulted in heterogenous responses, (2) statistically estimated interindividual differences in trainability, and/or (3) classified individual responses. We calculated effect sizes (ES_IR) to examine the presence of interindividual differences in trainability. We also compared response rates (n = 614) across classification approaches that considered neither, one of, or both errors and an SWC or MCID. We then sorted response rates from studies that also reported mean changes and response thresholds (n = 435 response rates) into four quartiles to confirm our ancillary hypothesis that larger mean changes produce larger response rates. Results: Our search revealed 3,404 studies, and 149 were included in our systematic review. Few studies (n = 9) statistically estimated interindividual differences in trainability. The results from these few studies present a mixture of evidence for the presence of interindividual differences in trainability because several ES_IR values lay above, below, or crossed zero. Zero-based thresholds and larger mean changes significantly (both p < 0.01) inflated response rates. Conclusion: Our findings provide evidence demonstrating why future studies should statistically estimate interindividual differences in trainability and consider error and an SWC or MCID when classifying individual responses to exercise training. Systematic Review Registration: [website], identifier [registration number].

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.