Interactive effects of acute experimental pain in trapezius and sored wrist extensor on the electromyography of the forearm muscles during computer work (original) (raw)
Related papers
European Journal of Applied Physiology, 2009
The aim of this laboratory study was to investigate acute eVects of experimental muscle pain on spatial electromyographic (EMG) activity of the trapezius muscle during computer work with active and passive pauses. Twelve healthy male subjects performed four sessions of computer work for 2 min in one day, with passive (relax) and active (30% maximum voluntary contraction of shoulder elevation) pauses given every 40 s without and with presence of experimental pain. Surface EMG signals were recorded from four parts of the trapezius. The centroid of exposure variation analysis along the time axis was lower during computer work with active pauses when compared with passive one in all muscle parts (P < 0.05). In presence of experimental pain, EMG amplitude increased in transverse and ascending parts and relative rest time decreased in ascending part. The results of this study showed a more variable trapezius activity pattern and increased activity with active compared with passive pauses, a lowered trapezius rest with presence of experimental pain, and increased activity in the transverse and ascending parts of trapezius due to experimental pain during computer work. Acute pain led to muscle activation pattern during computer work considered to increase the risk of developing work-related musculoskeletal disorders.
International Journal of Industrial Ergonomics, 2002
Work-related musculoskeletal disorders are frequent in workers with light to moderate load repetitive work, e.g. computer operators. The Cinderella hypothesis proposes that the development of chronic muscular pain is due to an overuse of fibers belonging to low-threshold motor units. The hypothesis requires that there exist motor units that are active (1) for a time long enough to actually damage the fibers, and (2) in different postures and throughout movements. In this study, the firing behavior of motor units in the extensor digitorum communis (EDC) muscle was registered in eight subjects during a 25-min static low-level contraction and during full range of motion wrist movements.
Muscle fatigue in relation to forearm pain and tenderness among professional computer users
Journal of Occupational Medicine and Toxicology, 2007
Background To examine the hypothesis that forearm pain with palpation tenderness in computer users is associated with increased extensor muscle fatigue. Methods Eighteen persons with pain and moderate to severe palpation tenderness in the extensor muscle group of the right forearm and twenty gender and age matched referents without such complaints were enrolled from the Danish NUDATA study of neck and upper extremity disorders among technical assistants and machine technicians. Fatigue of the right forearm extensor muscles was assessed by muscle twitch forces in response to low frequency (2 Hz) percutaneous electrical stimulation. Twitch forces were measured before, immediately after and 15 minutes into recovery of an extensor isometric wrist extension for ten minutes at 15 % Maximal Voluntary Contraction (MVC). Results The average MVC wrist extension force and baseline stimulated twitch forces were equal in the case and the referent group. After the fatiguing contraction, a decreas...
Archives of Physical Medicine and Rehabilitation, 2009
Objective: To examine the effect of wrist orthoses on the electromyography activities of the extensor carpi ulnaris, flexor digitorum superficialis, and fibers of the upper trapezius muscles during computer work. Design: A randomized, 3ϫ2 factorial design: orthoses (no orthosis, wearing a custom-made orthosis, wearing a commercial orthosis) and tasks (typing, using the mouse). Setting: Laboratory for biomechanics and rehabilitation. Participants: Healthy university students (Nϭ23), ranging from 18 to 26 years of age. Intervention: Study volunteers performed standardized tasks such as typing and using the mouse while wearing 1 of 2 types of wrist orthoses or no orthosis. Main Outcome Measures: We used surface electromyography and considered 100% maximum voluntary contraction to represent the amplitude of electromyographic activity. Results: We observed a significant increase in the electromyographic activity of the trapezius (PϽ.05) with the use of orthoses. No significant difference was observed in the activities of the flexor digitorum superficialis or extensor carpi ulnaris in participants who typed with or without orthoses (PϾ.05). However, when the participants used the mouse, the extensor muscle presented an increase in activity with both orthoses, and the same pattern was observed in the flexor muscle when the volunteers used the custom-made orthosis. Conclusions: Wrist orthoses affected the muscle activities in the upper limbs of healthy adults who were using a computer. Electromyographic activity increased in the trapezius when the subjects used either type of orthosis, and the same pattern was observed in the extensor carpi ulnaris when the subjects used the mouse. The flexor digitorum superficialis presented an increase in activity only when the subjects worked with the mouse and used a custom-made splint.
Journal of Electromyography and Kinesiology, 2003
The Cinderella hypothesis postulates the continuous activity of specific motor units (MUs) during low-level muscle contraction. The MUs may become metabolically overloaded, with the subject developing muscle pain and strain. The hypothesis requires MUs that are active for a time long enough to actually damage muscle fibers. The aim of this study was to determine if there are continuously active MUs in the right trapezius muscle during normal computer work using a computer mouse. Fourteen healthy subjects executed an interactive computer-learning program (ErgoLight) for 30 min. Six-channel intramuscular EMG and twochannel surface EMG signals were recorded from two positions of the trapezius muscle. Decomposition was achieved with automated, multi-channel, long-term decomposition software (EMG-LODEC). In two out of the 14 subjects, three MUs were continuously active throughout the 30 min. Although the majority of the MUs were active during only part of the experimental session, an ordered on-off behavior (e.g. substitution) pattern was not observed. As long-lasting activity was verified in some subjects, the results support the Cinderella hypothesis. However, it cannot be concluded here how long the MUs could stay active. If continuous activity overloads low threshold MUs, the potential exists for selective fibre injuries in low threshold MUs of the trapezius muscle in subjects exposed to long-term computer work.
Journal of Electromyography and Kinesiology, 1999
Firstly, upper trapezius EMG activity patterns were recorded on the dominant side of 6 industrial production workers and on the side operating a computer mouse of 14 computer-aided design (CAD) operators to study differences in acute muscular response related to the repetitiveness of the exposure. The work tasks were performed with median arm movement frequencies ranging from 5 min −1 to 13 min −1 and were characterized by work cycle times ranging from less than 30 sec to several days. However, the static and median EMG levels and EMG gap frequencies were similar for all work tasks indicating that shoulder muscle loads may be unaffected by large variations in arm movement frequencies and work cycle times. An exposure variation analyses (EVA) showed that the EMG activity patterns recorded during production work were more repetitive than during CAD work, whereas CAD work was associated with more static muscle activity patterns, both may be associated with a risk of developing musculoskeletal symptoms. Secondly, upper trapezius EMG activity patterns recorded on the mouse side of the CAD operators were compared with those recorded on the non-mouse side to study differences in muscular responses potentially related to the risk of developing shoulder symptoms which were more prevalent on the mouse side. The number of EMG gaps on the mouse side were significantly lower than the values for the upper trapezius on the non-mouse side indicating that more continous activity was present in the upper trapezius muscle on the mouse side and EVA analyses showed a more repetitive muscle activity pattern on the mouse side. These findings may be of importance to explain differences in the prevalence of shoulder symptoms.
Wrist and Shoulder Muscle Activity Changes Across Computer Tasks
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2002
The computer workstation is a ubiquitous tool in the office work environment; however, its use varies across many different tasks from surfing the Internet to typing. The question, therefore, is how does exposure to different physical risk factors for musculoskeletal disorders vary across tasks? Fifteen adults (10 females, 5 males) completed tasks simulating work at a computer workstation. The tasks were typing text, completing an html-based form, editing a document, a graphics task, and finally navigating through a series of web pages. During these tasks the muscle activity of the wrist prime movers and three shoulder muscle groups were recorded using surface EMG. For the wrist, the extensors were the most active ranging on average from 8 to 25 percent of Maximum Voluntary Contraction amplitude, with the greatest activity occurring in the typing task. The wrist activity decreased when the work changed from a keyboard-based activity to predominantly mouse-based activity. For the sho...
2007
Work related musculoskeletal disorders (WMSDs) in the shoulder/neck area are a common and increasing problem among European computer workers, especially women. Long-term low-level workloads with low degree of muscle rest are a potential risk factor for developing WMSDs. The purpose of the present study of female computer users (age 45-65 years) in Denmark and Sweden was to investigate if subjects with self-reported neck/shoulder complaints (cases, N = 35) show less trapezius muscle relative rest time (RRT) than controls (N = 44) when performing standardised short-term computer work tasks in controlled laboratory conditions. Surface electromyography (EMG) signals were recorded bilaterally from the upper trapezius muscles during a type, edit, precision and colour word stress task. Besides RRT, 10th percentile RMS values were calculated. On the average, 15 of the cases and 18 of the controls showed analysable EMG files per task. For the colour word stress task, the results showed lower RRT values and higher 10th percentile RMS amplitude levels among cases compared to controls. No such signs could be found for the other tasks performed. The present results indicate an increased motor response to a psychological stressor among subjects with self-reported neck/shoulder complaints.
Journal of Electromyography and Kinesiology, 2007
Work related musculoskeletal disorders (WMSDs) in the shoulder/neck area are a common and increasing problem among European computer workers, especially women. Long-term low-level workloads with low degree of muscle rest are a potential risk factor for developing WMSDs. The purpose of the present study of female computer users (age 45-65 years) in Denmark and Sweden was to investigate if subjects with self-reported neck/shoulder complaints (cases, N = 35) show less trapezius muscle relative rest time (RRT) than controls (N = 44) when performing standardised short-term computer work tasks in controlled laboratory conditions. Surface electromyography (EMG) signals were recorded bilaterally from the upper trapezius muscles during a type, edit, precision and colour word stress task. Besides RRT, 10th percentile RMS values were calculated. On the average, 15 of the cases and 18 of the controls showed analysable EMG files per task. For the colour word stress task, the results showed lower RRT values and higher 10th percentile RMS amplitude levels among cases compared to controls. No such signs could be found for the other tasks performed. The present results indicate an increased motor response to a psychological stressor among subjects with self-reported neck/shoulder complaints.
Fisioterapia em Movimento, 2014
Comparison of the electrical activity in upper trapezius and wrist extensor muscles during two typewriting conditions [I] Comparação da atividade elétrica dos músculos trapézio superior e extensores do punho em duas condições de digitação ] Abstract Introduction: The proper use of the position of the arm and wrist while typing may reduce muscle overload and prevent musculoskeletal disorders. Objective: To evaluate the electromyographic activity of upper trapezius and wrist extensor muscles during two typewriting conditions. Materials and methods: Six healthy females ( X age = 42 years, SD = 10), ( X height = 1.65m, SD = 0.05) and ( X weight = 71kg, SD = 16) participated in this study. The task was performed with a newly developed arm support and without the support. A perceived exertion scale was used with all subjects. An ANOVA with repeated measures was used to verify differences in perceived exertion and root mean square (RMS). Results: There were no statistically significant differences for the RMS between the typewriting tasks. The condition without arm support presented a significantly greater mean velocity and amount of words typed (P = 0.02; P = 0.03) and there was a significant difference in perceived exertion during the condition without arm support (P = 0.03). Electromyographic activity did not present differences. Conclusion: The muscle electrical activity was not altered regardless the arm support and occurred the improvement of the perceived exertion after 10 minutes of typing without support. Long-term studies are needed.