The hip flexor muscle (iliopsoas) may be rubbing over the pelvic wall.

Current methods of manual muscle testing are inadequate to isolate differences between the SCM and deep neck flexor muscle groups, both of which work in concert to produce a cervical flexion moment)5 Although the SCM mnscle makes the largest contribution of all the neck flexors to performing neck flexion, electromyographic (EMG) studies provide evidence that DNFs are active in this position and that they remain contracted in static and small phasic flexion contractions.

Works on: core postural muscles, inner/outer thighs, buttocks, hamstrings, quadriceps, hip flexor muscles.