Cervical flexion–relaxation response to neck muscle fatigue in males and females

A Comparison Study of Posture and Fatigue of Neck According to Monitor Types (Moving and Fixed Monitor) by Using Flexion Relaxation Phenomenon (FRP) and Craniovertebral Angle (CVA)

“…In this study, a document task was carried out for 50 min to compare the FRR values, which decreased from 3.11 before the document writing task to 2.79 after it ( Section 3.3 ); this means that the task of 50 min caused fatigue in the CES. This result was similar to those of previous studies [ 15 , 36 ]. Yoo et al (2011) also reported that FRR could be used to evaluate the potential risk of neck discomfort during computer work [ 37 ].…”

“…Each participant was paid at a rate of $15.00 per hour for participation. To identify the effect of neck health conditions, participants were divided into two groups (low-FRR and normal-FRR) based on the threshold FRR value of 2.5, which was used to identify the presence or absence of FRP [ 15 , 27 ]. The participants with FRR value higher than 2.5 (16 males) were placed in the normal-FRR group, and the remaining (seven males) were classified as the low-FRR group.…”

“… FRR: The FRR has been widely used to quantify the relaxation ability of the extensor muscles of the neck. The FRR, as calculated by using Equation (1), is defined as the ratio of the maximum EMG value in the extension phase (phase 4) to the average EMG value in the full flexion phase (phase 3), as shown in Figure 2 [ 15 ]. …”

“…The FRP of the cervical spine is similar to those observed for the ES muscle. In the cervical spine, during neck flexion, the cervical extensors (active structures) gradually increase their muscle activation to compensate for the increase in the head’s load [ 15 ]. When the head is fully flexed, the load on the muscles (active structures) is transferred to the passive structures, resulting in a reduction, or silence, of the myoelectric activity of muscles [ 16 ].…”

“…The FRP parameters, such as flexion relaxation ratio (FRR), have been widely used. FRR is defined as the ratio of the maximum activation in the re-extension phase to the average activation in the full-flexion phase (silence period) [ 15 ]. The FRR is a very useful indicator to distinguish between healthy subjects and those with neck pain [ 18 ] because patients experiencing neck pain have been reported to not show the FRP due to abnormal recruitment patterns.…”