Individuals with chronic low back pain have reduced myofascial force transmission between latissimus dorsi and contralateral gluteus maximus muscles

The thoracolumbar fascia is essential in lumbar stabilization and is considered a path of transmitting myofascial force. This study investigates whether there is a difference in the myofascial force transmission between latissimus dorsi and contralateral gluteus maximus in individuals with and without chronic low back pain (CLBP). Forty-eight individuals were divided into CLBP and control groups. Outcome variables were evaluated in two experimental conditions: relaxed and contracted latissimus dorsi. Lumbar stiffness was assessed using a non-invasive digital indentometer, and passive properties of the contralateral hip (resting position, torque and stiffness) were evaluated using an isokinetic dynamometer. Trunk and hip muscle activation was monitored with electromyography. Data were analyzed using two-way ANOVA. Latissimus dorsi contraction increased lumbar stiffness in both groups (p < 0.001) compared to the relaxed condition. However, only the control group showed a change in the hip resting position toward greater lateral rotation and an increase in passive hip torque with latissimus dorsi contraction compared to the relaxed condition (p < 0.001). Additionally, latissimus dorsi contraction led to a small and clinically non-relevant increase in passive hip stiffness (below the standard error of measurement) in both groups when compared to the relaxed condition. The results demonstrated that the myofascial force transmission between latissimus dorsi and contralateral gluteus maximus is reduced in individuals with CLBP, since the latissimus dorsi contraction changed the passive properties only in the adjacent tissues (lumbar region) but not in tissues more distant from the origin of the traction.