Associations between cervical and scapular posture and the spatial distribution of trapezius muscle activity

Ergonomic arm support prototype device for smartphone users reduces neck and shoulder musculoskeletal loading and fatigue

Smartphone use is a risk factor for both neck and shoulder musculoskeletal disorders. The objective of this study was to evaluate an ergonomic arm support prototype device, which may help improve posture while using a smartphone, by determining its effect on muscle activity, muscle fatigue, and neck and shoulder discomfort. Twenty-four healthy young adult smartphone users performed 20 min of smartphone game playing under two different conditions, smartphone use with support prototype device (i.e. intervention condition) and without (i.e. control condition), while neck and shoulder posture were controlled at 0° neck flexion and 30° shoulder flexion. Activity and fatigue of four muscles were measured using surface electromyography (sEMG), these were: anterior deltoid (AD), cervical erector spinae (CES), upper trapezius (UT) and lower trapezius (LT). The intervention condition showed significantly decreased activity of all muscles. Fatigue of all muscles, except LT, significantly increased over time compared to the start point in the control condition. There was no significant difference in muscle fatigue between each time point in the intervention condition. In conclusion, the ergonomic arm support prototype device can be used as ergonomic intervention to reduce neck and shoulder muscle loading and fatigue.

The impact of forward head posture on the electromyographic activity of the spinal muscles

Objective

This study aims to examine the electromyographic activity of the regional spinal muscle between patients with forward head posture (FHP) and those with a normal cranio-vertebral (CV) angle.

Methods

We recruited 60 adult women aged between 18 and 29 years from a single institution. The CV angle was measured in the sagittal plane, which helped us to assign the participants in the FHP group (n = 30) with a large CV angle (53.1 ± 2.3) and the control group (n = 30) with a normal CV angle (43.0 ± 3.6). The surface electromyography (EMG) was used to measure the magnitude of normalised muscle activity of eight spinal muscles (cervical, lumbar, and thoracic levels) while standing and performing a specific manual handling task.

Results

The CV angle was significantly lower in the FHP group than in the control group (p = .001). The cervical erector spinae (CES) muscle activity was significantly increased in the FHP group compared to that in the control group. The right and left CES of those in the FHP group exhibited 73% and 87%, respectively, higher normalised muscle activity than those in the control group while performing the manual handling task (p = .001). No significant difference was detected for the thoracic or lumbar segment muscles between groups.

Conclusion

Our results indicate that greater neck muscle demands result from anterior head translation in FHP. This effect is a counterbalance to the reduced CV angle and to support the neck. The increased activity of the neck muscles in FHP could demand more support from the neck muscles and might increase the risk of spinal injuries. Management of FHP is essential to avoid overloading the spinal muscles.

Differences in the activity of the shoulder girdle and lower back muscles owing to postural alteration while using a smartphone

The purpose of this study was to clarify the influence of different postures on the activity of the shoulder girdle and lower back muscles while using a smartphone. Sixteen healthy male participants maintained two postures while using a smartphone : a good posture in which the tragus and acromion were closer to the vertical line passing through the greater trochanter, and a poor posture in which the tragus and acromion were farther from the vertical line passing through the greater trochanter. The target muscles were the rhomboid major (Rhom), upper trapezius, middle trapezius, lower trapezius (LT), lumbar erector spinae (LES), and lumbar multifidus (LMF). The activities of the Rhom and LT were significantly lower with poor posture than those with good posture. The activities of LES and LMF were significantly higher with poor posture than those with good posture. The results of this study indicated that poor posture was associated with hypoactivity of the shoulder girdle muscles and hyperactivity of the lower back muscles when compared with good posture. Poor posture for prolonged periods while using a smartphone would lead to malfunction of the shoulder girdle muscles and musculofascial lower back pain. J. Med. Invest. 67 : 274-279, August, 2020.

Impaired Trunk Posture in Women With Fibromyalgia

STUDY DESIGN

A cross-sectional study.

OBJECTIVES

The main goal of the study was to analyze posture of Fibromyalgia syndrome (FMS) in women compared with healthy subjects to establish if posture assessment could be useful to characterize the syndrome. Secondarily, we explored the impact of sedentary behavior on trunk posture.

SUMMARY OF BACKGROUND DATA

Pain has been associated with poor static postures, however there is little information on the effect of FMS, which is characterized by widespread pain, on trunk posture.

METHODS

One hundred eighteen women with FMS and 110 healthy counterparts participated in this study, in which trunk posture was assessed. The thoracic kyphosis, forward head position, and shoulder position (basal and maximum protraction) were measured. Further, maximum shoulder protraction and the ability to maintain the cervical and thoracic angle were assessed. To compare the differences in posture depending on the grouping, an independent Student t test was conducted. To analyze the differences between groups in the ability to maintain the position over a period of time and the differences in posture depending on more or less active lifestyles, two multivariate analysis of variance were performed.

RESULTS

The results showed a significantly larger thoracic kyphosis, baseline shoulder protraction and lower craniovertebral angle and maximum protraction in FMG compared with CG (P < 0.05). FMG subjects exhibited an impaired ability to maintain the cervical and thoracic angles, as this varied throughout the test, unlike those of their counterparts. A sedentary lifestyle did not affect trunk posture in the FMS participants.

CONCLUSION

FMS female population present an altered trunk posture and an inability to maintain trunk position. Since this does not appear to be influenced by a more or less active lifestyle, specific treatment programs are needed to manage this clinical condition.

LEVEL OF EVIDENCE

2.

The effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity

[Purpose] To assess the effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity. [Subjects and Methods] Twenty-three female university students were evaluated. Muscle activity was assessed by a portable surface electromyography (sEMG) system (Myomonitor IV, Delsys, USA). Upper trapezius and anterior deltoid activity were recorded in five shoulder flexion postures: 0°, 15°, 30°, 45° and 60° and in two conditions: with the forearm supported and unsupported. Descriptive data analysis was performed and statistical analysis was conducted by a multivariate analysis of variance with three repeated factors (posture, support and side). [Results] Three-way interactions were not significant. Two-way interaction was significant for support and posture for both muscles, indicating that the muscular activity depends on the forearm support and shoulder posture. The forearm support reduced upper trapezius and anterior deltoid activity for all shoulder flexion angles. The mean and standard deviation for this decrease was 7.8 (SD=4.6)% of the maximal voluntary contraction for anterior deltoid and 3.8 (SD=2.0)% of the maximal voluntary contraction for upper trapezius. In the unsupported condition, increasing the shoulder flexion angle caused an increase in the upper trapezius and anterior deltoid activation. [Conclusion] These results highlight the importance of using forearm support and to maintain neutral shoulder posture, when the upper arms are not supported, to reduce muscle activation. Thus, this study provides evidence about the effect of these recommendations to reduce muscular activity.

Changes in neck and upper trunk muscle activities according to the angle of movement of the neck in subjects with forward head posture

[Purpose] This study investigated changes in neck and upper trunk muscle activities according to the angle of movement of the neck in subjects with Forward Head Posture. [Subjects and Methods] Twenty subjects with forward head postures were recruited. The activities of the sternocleidomastoid muscle, splenius capitis and splenius cervicis muscles, upper trapezius muscle, and middle trapezius muscle during flexion and extension were assessed. [Results] The activity of the sternocleidomastoid muscle showed significant differences between the 30° flexed position and the full range of motion position, and between the neutral position and the full ROM position. The activity of the middle trapezius muscle showed a significant reduction in the 30° extended position and the full ROM position as compared to the neutral position. [Conclusion] In the full flexed position, sternocleidomastoid muscle activity increased significantly, and during extension position, the middle trapezius muscle reduced its activities.