Electromyographic activity and cocontraction of trunk muscles during exercises performed with an oscillatory pole: an analysis of the effect of different postures

This study aimed at analyzing the electromyographic activity (EMG) and cocontraction of torso muscles during exercises with a flexi bar, in two different postures (neutral pelvis and posterior pelvic tilt). 20 young women with no lower back pain took part in the study (ages between 18 and 28 years) and they were recruited from a university population. In order to collect the data, an exercise was performed with a flexi bar being held with both hands. It was perpendicular to the ground and it was oscillating in the sagittal plane. That exercise was conducted in two different pelvis postures (neutral and posterior tilted). The EMG signals were collected bilaterally on the following muscles: internal oblique (IO), rectus abdominals (RA), iliocostalis lumborum (IL) and multifidus (MU). The analysis of variance (ANOVA) of repeated measurements was found to display an interaction between muscles and postures (F=5.18; p=0.003). The activation of IL muscle in the neutral posture was 7.93% higher than in the posteriorly tilted posture (p=0.005), and the activation of IO muscle was 13.62% higher in the posteriorly tilted posture than during the exercise in the neutral posture (p=0.002). According to our results, the performance of the exercise with a posteriorly tilted pelvis increased the activation of IO muscle, whereas IL muscle was found to have a higher activation when the exercise was performed in a neutral posture. Future studies need to be conducted in order to understand the neuromuscular adaptations that are generated by exercises with flexi bars, and their relevance to the prevention and treatment of nonspecific lower back pain.