Effects of static stretching and strengthening exercises on flexion relaxation ratio in patients with LBP: A randomized clinical trial

Introduction: Stretching and strengthening exercises are commonly used to improve muscle shortness. Consequently, the aim of this trial was to compare the flexion-relaxation response (electromyography activities of shortened hamstring and back muscles) in chronic nonspecific LBP patients. Methods: In this randomized controlled clinical trial, forty-five eligible patients were randomly categorized into three groups; static stretching (n = 15), strengthening exercise in lengthened hamstring position (n = 15) and control (n = 15). All groups received conventional physical therapy for LBP and the two intervention groups received special exercise programs as well. Each group performed three treatment sessions for a week, a total of 12 sessions. The flexion-relaxation ratio (FRR) for knee and back muscles were assessed as the primary outcome measure. Pain and functional disability for participants were also assessed. Results: The results indicated non-significant differences between the three groups regarding the changes of FRR (mean between-group differences ranged over 0.69 to 39.1; p > 0.05), pain and disability (mean between-group differences ranged over 0.15 to 5.96; p > 0.05). Within-group analysis for each group, revealed statistically significant improvement in the patients' score of either pain (mean within group differences ranged over-27.20 to-35.76; p < 0.001) or disability (mean within-group differences ranged over-16.17 to 24.95; p < 0.001) as secondary outcomes. In other words, the scores of pain and disability decreased in all treatment groups as compared to the baseline. Conclusion: Neither static stretching nor strengthening exercises in lengthened hamstring position affected FRR more than the control group.(c) 2022 Published by Elsevier Ltd.