The Effect of Backpack Loads on FRR (Flexion-relaxation Ratio) in the Cervical Spine

Abstract

[Purpose] This study examined the effects of various backpack loads on the cervical flexion relaxation ratio as a quantitative neurological measure. [Subjects] Fourteen subjects with no neck pain participated in the study. [Methods] Surface electromyograms of the C4 paraspinal muscles were measured bilaterally, while subjects performed cervical flexion extension, and normalized in three phases. Cervical FRR data of three different backpack loads were analyzed. The FRR was calculated as the muscle activation during the cervical extension phase divided by the muscle activation during the relaxation phase. [Result] The FRR in the unloaded condition was 2.44 on the right and 2.37 on the left; for the backpack weighing 10% BM, the FRR were 1.91 and 1.89, respectively, and for the 20% BM backpack, FRR were 1.56 and 1.53, respectively. [Conclusion] A heavier backpack increased the potential for neck pain. The FRR is a functional examination that can be used to quantitatively assess the potential for developing cervical pain and the results of intervention.