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Study protocol and determination of three head positions. (A) All participants were asked for the maximal voluntary contraction (MVC) of head extension twice. After MVC measurements, participants held the sitting posture for 30 min, and electromyography measurements were taken for 1 min at the beginning of the posture and for 1 min every 10 min thereafter (gray bar). (B) Looking straight ahead and adjusting the seat recline, the most comfortable head and neck position is the neutral head position. X indicates the distance between the back of the head and the seat. (C) The neutral position was defined as the posture with the 5° recline folded down from the neutral head position (θ′ = 5°). A pillow with a height of x was fabricated for each participant, and the participant was made to lean against the pillow. (D,E) The position with the pillow height 3 cm higher or lower than the neutral position was defined as the + 3 position or − 3 position (y = x + 3 cm and z = x − 3 cm).
Source publication
Forward head posture (FHP) is a serious problem causing head and neck disability, but the characteristics of muscle activity during long-term postural maintenance are unclear. This study aimed to investigate a comparison of electromyography (EMG) activation properties and subjective fatigue between young adults with and without habitual FHP. In thi...
Citations
... In a systematic review conducted in 2020, it was stated that there was no definite CVA value that could show FHP (28). However, the most commonly used cut-off values of the CVA angle to identify individuals with FHP in studies are 48° (5, 29, 30) -50° (3, 31, 32) and 53° (7,33,34). There are also studies using the distance measurement from the line passing through the acromion to the line passing through the external acoustic meatus to identify individuals with/without FHP. ...
Forward head posture (FHP), which is defined as a forward displacement of the head on the cervical spine, is a common postural disorder. It is suggested that this malalignment alters the loads on the spine, affects the length-tension relationship in muscles, and changes muscle activation. Therefore, the aim of this review is to investigate the results of studies on the examination of the changes exerted by FHP on muscle activation. Although there are many methods used to assess FHP, there is no standard clinical method for accurate measurement of this angle. Photographic measurement is the most widely used, valid, and reliable assessment method. Craniovertebral angle (CVA) is the most widely used value to assess FHP in photographic measurements. A CVA of less than 48-50° is defined as FHP, although there are differences regarding the norm value of the CVA. There are many studies on the assessment of differences in the activation of the neck and shoulder muscles by making FHP and non-FHP classifications according to the CVA to show the changes in muscle activation in individuals with FHP. Although many studies have shown increased sternocleidomastoideus and upper trapezius activation, there are also others indicating no difference. Similar conflicting results exist for the lower trapezius and serratus anterior muscles. Although there are conflicting results regarding muscle activation in studies, it seems likely that muscle activation is altered in individuals with FHP. It may be recommended that physiotherapists conduct interventions by considering these differences in muscle activation in individuals with FHP.
... 27 Furthermore, increased activity in the UT and pectoralis major but decreased activity in the SA and middle trapezius were observed during shoulder abduction with FHP. 28 30,31 Because of mild FHP, it is suggested that there might be no significant correlation between FHP and muscular activation in the present study. In addition, when the posture is stable, the muscle activity increased in the SA and pectoralis major as the load increased, but the UT showed constant muscle activity. ...
... In this study, however, there was no correlation between FHP and the difference in muscle activation during shoulder flexion and abduction. In previous studies reported that FHP changed according to the muscle length and muscle tension, such as sternocleidomastoid, neck extensor, trapezius, SA, and pectoralis.7,[29][30][31] In FHP, increased muscle activation of the UT and decreased muscle activation of the SA were noted during shoulder flexion and abduction.[26][27][28]31 ...
... 15 People with FHP showed abnormal electromyographic (EMG) activity in the neck muscles, and it was reported that shoulder muscles, such as the serratus anterior and trapezius muscle, were also negatively affected. 12,16 Objective and quantitative clinical investigations are important in determining the precise diagnosis for patients with musculoskeletal dysfunctions, such as FHP and neck problems. 2,7 Many previous studies related to FHP and the kinesiologic function of the shoulder complex reported the effects of FHP on EMG activity of the shoulder muscles, such as the upper trapezius, serratus anterior, or lower trapezius. ...
... 2,7 Many previous studies related to FHP and the kinesiologic function of the shoulder complex reported the effects of FHP on EMG activity of the shoulder muscles, such as the upper trapezius, serratus anterior, or lower trapezius. 12,16 Although high-quality kinetic and kinematic evaluations, such as a 3D motion analysis and EMG devices, are used to investigate the relationship between FHP and shoulder dysfunction, most of the studies have mainly focused on shoulder muscle activity or neck pain. 2,3,16 In addition, studies verifying the effect of artificial FHP on the kinetics and kinematics of the shoulder joint using internal and external movement tasks are insufficient. ...
... 12,16 Although high-quality kinetic and kinematic evaluations, such as a 3D motion analysis and EMG devices, are used to investigate the relationship between FHP and shoulder dysfunction, most of the studies have mainly focused on shoulder muscle activity or neck pain. 2,3,16 In addition, studies verifying the effect of artificial FHP on the kinetics and kinematics of the shoulder joint using internal and external movement tasks are insufficient. ...
... An issue that is not typically addressed when assessing sitting posture is the presence of pre-existing spinal misalignment or poor postures. FHP is a common poor posture that is associated with a greater load transmitted to the neck [16,17], greater muscle activation and fatigue [18], lower endurance of the deep neck extensors and flexors [19], as well as substantial effects on the biomechanics of the nervous system by causing unfavorable mechanical strain [20,21], which causes the blood vessels to constrict [22] and the nerve root sleeves to unfold and become taut, predisposing individuals to altered or inefficient neurophysiological symptoms [23,24]. Accordingly, we believe the combined effects of sitting with a pre-existing FHP may likely exacerbate any overstraining of the spine and soft tissues, including any neurophysiological effects. ...
... Some authors have noted that an erect sitting posture [14,15] may lead to increased levels of fatigue resulting from increased muscle activation compared with the habitual sitting posture of an individual. In contrast, Nishikawa et al. [18] identified that FHP compared to NHP was associated with a greater cervical spine muscle activity and subjective fatigue using high density surface EMG. These seemingly contradictory findings are challenging to explain and likely involve complex interactions between an individual's perception of their natural posture, specific spine geometric alignments of the sagittal plane curvatures, muscle length tension relationships, and yet-undetermined variables. ...
The current study aimed to determine whether participants with and without forward head posture (FHP) would respond differently in cervical nerve root function to various sitting positions. We measured peak-to-peak dermatomal somatosensory-evoked potentials (DSSEPs) in 30 participants with FHP and in 30 participants matched for age, sex, and body mass index (BMI) with normal head posture (NHP), defined as having a craniovertebral angle (CVA) >55 •. Additional inclusion criteria for recruitment were individuals between the ages of 18 and 28 who were in good health and had no musculoskeletal pain. All 60 participants underwent C6, C7, and C8 DSSEPs evaluation. The measurements were taken in three positions: erect sitting, slouched sitting, and supine. We identified statistically significant differences in the cervical nerve root function in all postures between the NHP and FHP groups (p < 0.001), indicating that the FHP and NHP reacted differently in different positions. No significant differences between groups for the DSSEPs were identified for the supine position (p > 0.05), in contrast to the erect and slouched sitting positions, which showed a significant difference in nerve root function between the NHP and FHP (p < 0.001). The NHP group results were consistent with the prior literature and had the greatest DSSEP peaks when in the upright position. However, the participants in the FHP group demonstrated the largest peak-to-peak amplitude of DSSEPs while in the slouched position as opposed to an erect position. The optimal sitting posture for cervical nerve root function may be dependent upon the underlying CVA of a person, however, further research is needed to corroborate these findings.
Prolonged sitting is postulated to influence musculoskeletal performance (cervical flexor endurance, balance, and agility), discomfort and alter cervical spine angles during work-based computer use. Stair climbing breaks may be a great addition at typical and home offices however remain unexplored for its impact on musculoskeletal performance. In our counterbalanced pilot crossover trial, 24 adults were randomised to three interventions: (1) prolonged sitting, (2) interrupted by 2 min of self-paced, and (3) externally paced stair climbing for 2 h. Cervical spine angles were measured every 30 min while balance, agility, endurance, and discomfort were assessed before and after 120 min. Stair climbing interruptions have favourable effects on agility (F = 8.12, p = 0.009, ηp2 = 0.26) and musculoskeletal discomfort, but failed to improve other musculoskeletal outcomes associated with prolonged sitting. Brief stair climbing interruptions are effective in improving discomfort and agility while pragmatic trials are warranted for translated effects.
