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

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.

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.

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.

Neither static stretching nor strengthening exercises in lengthened hamstring position affected FRR more than the control group.