Effects of Cervical Flexion on the Flexion-relaxation Ratio during Smartphone Use

Abstract

[Purpose] The purpose of this study was to measure the cervical flexion-relaxation ratio (FRR) and intensity of neck pain and identify the differences according to postures adopted while using smartphones. [Subjects] Fifteen healthy adults with no neck pain, spinal trauma, or history cervical surgery participated in this study. [Methods] The activity of the cervical erector spinae muscle was recorded while performing a standardized cervical flexion-extension movement in three phases (flexion, sustained full flexion, extension). And neck pain intensity was recorded using a visual analog scale (VAS) with values between 0 and 10. Postures held while using a smartphone are distinguished between desk postures and lap postures. The FRR was calculated by dividing the maximal muscle activation during the extension phase by average activation during the complete flexion phase. [Results] No significant differences were found in the FRR between desk posture, lap posture, and baseline, though the intensity of the neck pain increased in the lap posture. [Conclusion] The FRR could be a significant criterion of neuromuscular impairment in chronic neck pain or lumbar pain patients, but it is impossible to distinguish neck pain that is caused by performing task for a short time. Prolonged lap posture might cause neck pain, so the use of smartphones for a long time in this posture should be avoided.

Smartphone and Musculoskeletal Risk Factors: A Systematic Review

“…The participants in the reviewed studies were primarily females (136 females and 116 males) and were in their 20s [2,5,8,11,[14][15][16][17][18][19][20][21][22]. Some of the study participants were more than 30 years old [11][12][13][14][15]; one study did not specify the age of the subjects.…”

“…Eight articles indicated that the participants are right handed [2,16,18,20,21,[23][24][25][26][27]. In terms of phone characteristics, two studies used emulated phones with physical keypads [18,25], most of the studies involved SPs with touchscreens [2,5,8,15,16,[19][20][21]23,24,26,27], two examined mobile phones with physical keypads [14,22], and one examined two kinds of mobile phones with physical keypads and touchscreens [11]. In each study, the participants executed different tasks, among which the most frequently assigned were typing and sending messages [14,22].…”

“…In some of the studies, the participants were asked to type 300 characters or only one or two sentences [16,17,22]. Task duration varied from 5 seconds [5,25] to 90 minutes [21]. One study evaluated various postures in three phases to determine the effects of posture on neck flexion [5].…”

“…Task duration varied from 5 seconds [5,25] to 90 minutes [21]. One study evaluated various postures in three phases to determine the effects of posture on neck flexion [5].…”

“…Prolonged neck flexion while using SPs increases the risk of neck pain as it injures the vertebral bodies of the neck [2,5,6]. Gustaffson, et al [7] in a cohort study on 7,092 SP users showed that after one year, the participants with no history of musculoskeletal disorders experienced pain in their hands and fingers, and the participants with a history of pain exhibited susceptibility to chronic neck and upper back disorders.…”