Epimuscular myofascial force transmission between the levator scapulae muscle and the upper fiber of the serratus anterior or rhomboid minor muscles.

ABSTRACT

BACKGROUND: This study investigated the epimuscular myofascial force transmission between the levator scapulae, serratus anterior, and rhomboid minor muscles. METHODS: The participants included 10 healthy males (a total of 20 shoulders). Differences in the shear moduli of the levator scapulae, serratus anterior, and rhomboid minor muscles were measured in the resting and levator scapulae stretching positions using shear wave elastography. The correlation between the rates of change for each muscle was also verified. FINDINGS: The results demonstrated a notable increase in the shear modulus from the resting to stretching positions for levator scapulae (42.9 ± 17.6 kPa vs. 52.4 ± 15.2 kPa) and serratus anterior (32.8 ± 12.9 kPa vs. 58.4 ± 18.5 kPa) (P = 0.02, P < 0.01). However, there was no significant difference in the shear modulus for the rhomboid minor between the resting (44.0 ± 19.2 kPa) and stretching (41.0 ± 20.2 kPa) positions (P = 0.40). Moreover, a significant positive correlation was observed between rates of change for the levator scapulae and serratus anterior muscles (P = 0.04, r = 0.459). INTERPRETATION: These findings indicate that the shear modulus of the serratus anterior increased with the stretching of the levator scapulae, suggesting the occurrence of epimuscular myofascial force transmission between these two muscles with different muscle insertions.