J Korean Phys Ther.  2020 Dec;32(6):378-382. 10.18857/jkpt.2020.32.6.378.

A Comparison Study of Cervical Flexion-Relaxation Ratio in the Normal and Forward Head Postures

• Yeo SS
• Kwon JW

• KMID: 2520088
• DOI: http://doi.org/10.18857/jkpt.2020.32.6.378

Abstract

Purpose
This study aimed to examine the effects of forward head posture on the flexion-relaxation ratio (FRR) and muscle activity during sustained neck flexion and to investigate the correlation between craniovertebral angle and FRR.
Methods
Nineteen subjects participated in this study and were allocated to a forward head posture (FHP) group or a non-forward head posture (NFHP) group. Craniovertebral angle (CVA) and FRR were measured in all subjects, and all participants performed a standardized cervical flexion-extension movement in two phases: Phase I, sustained cervical full flexion for 5s; and Phase II, cervical extension with the return to the starting position for 5s. The value of CVA has calculated three times, and the value of FRR was measured three times in order to obtain the mean value.
Results
FRR values in the FHP and NFHP group were significantly different (p<0.05). Phase I was significantly different, but the Phase II was not significantly different between the FHP and NFHP group (p>0.05). There was a significant correlation between the muscle activity of Phase I and CVA (p<0.05). However, FRR and the muscle activity of the Phase II were not a significant correlation with the CVA (p>0.05).
Conclusion
FHP increases the muscle activity of the cervical erector spinae during sustained neck flexion and reduces FRR, which can cause fatigue in the cervical erector spinae. In addition, for those with a smaller CVA, muscle activity of the cervical erector spinae is increased during sustained neck flexion, which can increase neck muscle tension.

Keyword

Forward head posture; Flexion-relaxation ratio; Craniovertebral angle