Changes in the flexion relaxation response following an exercise intervention

Study Design. Pre and post 12-week training study using surface electromyography to measure the flexion relaxation response. Objective. To evaluate whether the active or passive phases of the flexion relaxation measurement changes following an exercise intervention in patients with low back pain. Summary of Background Data. Impaired neuromuscular activation is an area of specific interest in patients with chronic nonspecific low back pain (LBP). The flexion relaxation phenomenon is commonly measured in LBP patients; however, there is insufficient evidence about the changes in this measure following an intervention. Methods. Fifteen subjects with chronic LBP ( 7 females, 8 males) performed a 12-week training intervention. The main outcome measures were the Oswestry disability index, visual analog scale, and flexion relaxation response analyzed by the raw electromyograph (EMG) signal, the relative EMG signal, and the flexion relaxation ratio. Results. Disability and pain scores improved significantly after the 12-week intervention. There were no changes in the active components of the flexion relaxation measurement but an approximate 67% decrease in the amount of activity measured during the relaxation phase at full trunk flexion. Conclusion. The data suggest that afferent feedback changes may be explaining why there is improved electrical relaxation following an exercise intervention.