Effects of Craniocervical Flexion on Suprahyoid and Sternocleidomastoid Muscle Activation in Different Exercises

This study aims to investigate the effects of craniocervical flexion (CCF) on the activation of suprahyoid and sternocleidomastoid (SCM) muscles in Shaker and Resistant Jaw Opening (RJO) exercises, and to compare the effects of these two exercises on the same muscles with the Chin Tuck Against Resistance (CTAR) exercise. The study recruited a total of 37 healthy participants (20 female and 17 male, mean age: 27.45 ± 7.32 years). All participants received craniocervical flexion training with the biofeedback pressure unit (Stabilizer™, Chattanooga Group Inc. USA). Shaker, Shaker with CCF, RJO, RJO with CCF and CTAR exercises were performed and surface electromyographic (sEMG) activations of the suprahyoid and SCM muscles were recorded. In addition, the maximum sEMG activations of suprahyoid and SCM muscles were recorded for the normalization procedure. CCF increased the effect of Shaker exercise on the suprahyoid muscle activation (p < 0.001); but this effect was not seen in RJO exercise (p > 0.05). Suprahyoid muscle activation was lower in Shaker exercise compared to RJO and CTAR exercises (p < 0.016). SCM muscle activation was greater in CTAR exercise compared to Shaker and RJO exercises (p < 0.016). The addition of CCF to the Shaker and RJOE exercises did not affect the ranking among the three exercises for both the suprahyoid and SCM muscles. The result of this study suggest that integration of CCF movement to the Shaker exercise would have a greater therapeutic effect. In addition, RJO exercise can be included in the rehabilitation program as an alternate to CTAR exercise.