Role of Posterior Layer of Thoracolumbar Fascia in Epimuscular Myofascial Force Transmission From Gluteus Maximus to Latissimus Dorsi and Lower Trapezius.

Purpose. Posterior layer of thoracolumbar fascia (PTLF) is the part of the deep fascia of back of the trunk which connects the trunk, upper and lower limb muscles. PTLF is the major myofascial linkage where myofascial force transmission can take place between the muscles attached to it. The present study evaluates the force transmission through PTLF to the right and left latissimus dorsi, and right and left lower trapezius muscles during isometric contraction of right and left gluteus maximus. Materials and methods. Present descriptive observational study was conducted on 40 male adult healthy volunteers aged between 30 to 45 years. The Root mean square (RMS) value of EMG signal of the bilateral gluteus maximus, latissimus dorsi and lower trapezius muscles was collected using surface Electromyographic sensors. The Electromyographic assessment was carried out at normal contraction, at minimum resistance (load of 1 kg) and at maximum voluntary contraction with resistance (2-5.5 kg) of gluteus maximus. Results. When left gluteus maximus contracts normally (without any resistance), the mean RMS value was found to be 16.28 ± 3.15 µV and on maximum voluntary contraction (MVC) with resistance it was 28.95 ± 4.89 µV. When right gluteus maximus contracts normally without any resistance, the mean RMS value was found to be 25.83 ± 4.48 µV and MVC with resistance was 43.70 ± 2.60 µV. This showed around 30-70% increase in RMS value from normal contraction to MVC with resistance. The relative activation at different isometric contractions of right and left gluteal muscles were compared to the right and left latissimus dorsi and right and left lower trapezius muscles. A significant (p < 0.001) Pearson's correlation was observed between the muscles. Conclusions. Epimuscular myofascial force is transferred from the gluteus maximus muscles to other muscles attached to PTLF directly or indirectly to the same side as well as to the opposite side. The connection via PTLF to the muscles attached to it may affect the sensory feedback and thereby the neuromuscular control. In pathological conditions, same myofascial linkage may contribute to altered biomechanics of the back of the trunk. [ABSTRACT FROM AUTHOR]