Alterations in cervical muscle activity in functional and stressful tasks in female office workers with neck pain

Considerations in the physical rehabilitation of patients with whiplash-associated disorders

STUDY DESIGN

Review of research identifying physical impairments in the neuromuscular system in subjects with whiplash-associated disorders.

OBJECTIVE

Review the impairments in movement and neuromuscular function toward constructing research informed exercise programs.

SUMMARY OF BACKGROUND DATA

Pain and injury to the musculoskeletal system result in loss of motion and impaired neuromuscular function which impacts on functional activities, work and quality of life. Therapeutic exercise is a mainstay of rehabilitation, but the nature of the exercises prescribed are currently various and the effect sizes of current programs for patients with whiplash-associated disorders are modest at best.

METHODS

A review was undertaken of research investigating the changes in cervical motion and neuromuscular function to better inform exercise prescription and identify areas for future research. RESULTS.: Reduced range of movement as well as pathological movement patterns (reduced acceleration and velocity, reduced smoothness and irregular axes of neck movement) have been documented in subjects with whiplash-associated disorders. In relation to neuromuscular control, changes have been demonstrated in neck muscles' spatial and temporal relationships as well as in their strength and endurance. The presence or not and the extent of changes is highly variable between individuals and appears to have some relationship to pain intensity. It appears that there is a need for specificity in exercise prescription to address particular impairments rather than the use of generic programs. High pain intensity can modify effects of a therapeutic exercise program.

CONCLUSION

Pain and injury result in reorganization of the motor control strategies of neck muscles and movement. Further research is required to determine if outcomes after a whiplash injury can be improved by using research informed, individually prescribed exercise programs matched to the individual's presentation. Research into best methods of pain management is also required to facilitate physical rehabilitation.

Influence of pain location and hand dominance on scapular kinematics and EMG activities: an exploratory study

Background

Assessment of three-dimensional kinematics and electromyography (EMG) activities is common in patients with chronic neck pain. However, the effect of hand dominance and neck pain location on the measurement of movement and EMG characteristics is still unclear. Therefore, the purpose of this study was to investigate the effect of neck pain location and arm dominance on the scapular kinematics and muscle EMG activities in patients with chronic neck pain.

Methods

Thirty subjects (10 males, 20 females; mean age (sd): 38 (11.9) years) with chronic neck pain for more than 3 months were recruited. The scapular kinematics and EMG activity of the upper trapezius and sternocleidomastoid muscles were measured during the bilateral arm elevation task. The three-way repeated measures ANOVA was used to examine the effect of neck pain location and hand dominance on the measurement of kinematics and EMG muscle activities.

Results

The movement of scapular posterior tilt was significantly influenced by arm dominance (P = 0.001) and by the interaction of arm dominance and elevation angle (P = 0.002). The movement of scapular upward/downward rotation was affected by the interaction of arm dominance and elevation angle (P = 0.02). The location of pain did not show any significant influence on the scapular movement and muscle activities.

Conclusions

Hand dominance could have an influence on the scapular kinematics, which should be taken into consideration when describing and comparing neuromuscular characteristics in individuals with chronic neck pain.

Effects of physical and mental task demands on cervical and upper limb muscle activity and physiological responses during computer tasks and recovery periods

The present study examined the effects of physical and mental workload during computer tasks on muscle activity and physiological measures. Activity in cervical postural muscles and distal forearm muscles, heart rate and blood pressure were compared among three tasks and rest periods of 15 min each in an experimental study design. Fourteen healthy pain-free adults participated (7 males, mean age = 23.2 ± 3.0 years) and the tasks were: (1) copy-typing ("typing"), (2) typing at progressively faster speed ("pacing"), (3) mental arithmetic plus fast typing ("subtraction"). Typing task was performed first, followed by the other two tasks in a random order. Median muscle activity (50th percentile) was examined in 5-min intervals during each task and each rest period, and statistically significant differences in the "time" factor (within task) and time × task factors was found in bilateral cervical erector spinae and upper trapezius muscles. In contrast, distal forearm muscle activity did not show any significant differences among three tasks. All muscles showed reduced activity to about the baseline level within first 5 min of the rest periods. Heart rate and blood pressure showed significant differences during tasks compared to baseline, and diastolic pressure was significantly higher in the subtraction than pacing task. The results suggest that cervical postural muscles had higher reactivity than forearm muscles to high mental workload tasks, and cervical muscles were also more reactive to tasks with high physical demand compared to high mental workload. Heart rate and blood pressure seemed to respond similarly to high physical and mental workloads.

Functional anatomy of human scalene musculature: rotation of the cervical spine

OBJECTIVES

Actions of the scalene muscles include flexion and lateral flexion of the cervical spine and elevation of the first and second ribs. The cervical rotational qualities of the scalene muscles remain unclear. Textbooks and recent studies report contradictory findings with respect to the cervical rotational properties of the scalene muscles. The present study was designed to take a mechanical approach to determining whether the scalene muscles produce rotation of the cervical spine.

METHODS

The scalene muscles were isolated, removed, and replaced by a durable suture material. The suture material was attached at the origin and then passed through a hole on the corresponding rib near the central point of the insertion. The suture material was pulled down through the corresponding costal insertion hole to simulate contraction of each muscle.

RESULTS

The simulated anterior, middle, and posterior scalene muscles, working independently and jointly, produced ipsilateral rotation of the cervical spine. The upper cervical spine rotated in the ipsilateral direction in response to the simulated muscle contraction. Findings were similar for the lower cervical spine with the exception of 2 specimens, which rotated contralaterally in response to the simulation.

CONCLUSION

Experimental models of the scalene muscles are capable of producing ipsilateral rotation of the cervical spine. The findings of this study support the accepted main actions of the scalene muscles. The clinical applications for understanding the cervical rotational properties of the scalene muscles include the diagnosis, management, and treatment of cervical pain conditions as well as thoracic outlet syndrome.

During computing tasks symptomatic female office workers demonstrate a trend towards higher cervical postural muscle load than asymptomatic office workers: an experimental study

QUESTIONS

Do symptomatic female office workers perform computing tasks with higher cervical postural muscle loads (in terms of higher amplitudes and less muscular rest) and more discomfort compared with asymptomatic individuals? Are these differences in postural muscle loads consistent across bilateral (typing) and unilateral (mousing) conditions?

DESIGN

an experimental case-control study.

PARTICIPANTS

18 symptomatic female office workers and 21 asymptomatic female office workers.

INTERVENTION

Three conditions (typing, mousing, and type-and-mouse) were performed in random order.

OUTCOME MEASURES

Muscle load was measured as median amplitude and gap frequency using surface EMG of bilateral cervical erector spinae and upper trapezius. Discomfort was measured using a numerical rating scale.

RESULTS

The case group demonstrated 4.3% (95% CI 0.1 to 8.4) higher amplitude during typing and 3.5% (95% CI 0.1 to 6.9) higher amplitude during type-and-mouse in the right cervical erector spinae compared with the control group. There was a similar difference between groups in the left cervical erector spinae which also demonstrated a 1.2 gaps/min (95% CI -2.3 to 0.0) lower frequency during typing. The case group had significantly higher discomfort during all conditions compared with the control group. The case group demonstrated higher median amplitudes and lower gap frequencies than the control group during bilateral conditions (typing and type-and-mouse) compared with unilateral conditions (mousing) for both muscle groups.

CONCLUSION

There was increased amplitude and decreased muscular rest in the cervical erector spinae of office workers performing typing and mousing tasks. These findings may represent a mechanism underlying computer-related musculoskeletal disorders.

Physiological responses to low-force work and psychosocial stress in women with chronic trapezius myalgia

Background

Repetitive and stressful work tasks have been linked to the development of pain in the trapezius muscle, although the underlying mechanisms still remain unclear. In earlier studies, it has been hypothesized that chronic muscle pain conditions are associated with imbalance in the autonomic nervous system, predominantly expressed as an increased sympathetic activity. This study investigates whether women with chronic trapezius myalgia show higher muscle activity and increased sympathetic tone at baseline and during repetitive low-force work and psychosocial stress, compared with pain-free controls.

Methods

Eighteen women with chronic trapezius myalgia (MYA) and 30 healthy female controls (CON) were studied during baseline rest, 100 min of repetitive low-force work, 20 min of psychosocial stress (Trier Social Stress Test, TSST), and 80 min recovery. The subjects rated their pain intensity, stress and energy level every 20 min throughout the experiment. Muscle activity was measured by surface electromyography in the trapezius muscle (EMGtrap) and deltoid muscle (EMGdelt). Autonomic reactivity was measured through heart rate (HR), skin conductance (SCL), blood pressure (MAP) and respiration rate (Resp).

Results

At baseline, EMGtrap, stress ratings, and HR were higher in MYA than in CON. Energy ratings, EMGdelt, SCL, MAP and Resp were, however, similar in the two groups. Significant main group effects were found for pain intensity, stress ratings and EMGtrap. Deltoid muscle activity and autonomic responses were almost identical in MYA and CON during work, stress and recovery. In MYA only, pain intensity and stress ratings increased towards the end of the repetitive work.

Conclusion

We found increased muscle activity during uninstructed rest in the painful muscle of a group of women with trapezius myalgia. The present study could not confirm the hypothesis that chronic trapezius myalgia is associated with increased sympathetic activity. The suggestion of autonomic imbalance in patients with chronic local or regional musculoskeletal pain needs to be further investigated.