title: The Effects of Work Pace on Within-Participant and Between-Participant Keying Force, Electromyography, and Fatigue Shoulder muscle activity in young and older people during a computer mouse task. Effect of computer mouse gain and visual demand on mouse clicking performance and muscle activation in a young and elderly group of experienced computer users. Muscle activity during computer-based office work in relation to self-reported job demands and gender Influence of time pressure and verbal provocation on physiological and psychological reactions during work with a computer mouse Differential effects of mental load on proximal and distal arm muscle activity The effect of physical and psychosocial loads on the trapezius muscle activity during computer keying tasks and rest periods Stress-induced muscle effort as a cause of repetitive strain injury? Muscle activity and cardiovascular response during computer-mouse work with and without memory demands Effects of physical and mental task demands on cervical and upper limb muscle activity and physiological responses during computer tasks and recovery periods
abstract: A laboratory study was conducted to determine the effects of work pace on typing force , electromyographic ( EMG ) activity , and subjective discomfort . We found that as participants typed faster , their typing force and finger flexor and extensor EMG activity increased linearly . There was also an increase in subjective discomfort , with a sharp threshold between participants ' self-selected pace and their maximum typing speed . The results suggest that participants self-select a typing pace that maximizes typing speed and minimizes discomfort . The fastest typists did not produce significantly more finger flexor EMG activity but did produce proportionately less finger extensor EMG activity compared with the slower typists . We hypothesize that fast typists may use different muscle recruitment patterns that allow them to be more efficient than slower typists at striking the keys . In addition , faster typists do not experience more discomfort than slow typists . These findings show that the relative pace of typing is more important than actual typing speed with regard to discomfort and muscle activity . These results suggest that typists may benefit from skill training to increase maximum typing speed . Potential applications of this research includes skill training for typists OBJECTIVE Assessment of the age effect in relation to computer work . BACKGROUND Increasingly , more older people are using computers , while hardware and software are not design ed with special consideration of their needs . METHODS Eight young and nine older females performed different computer mouse tasks .  Shoulder muscle activity was recorded from the right deltoid muscle , right and left upper trapezius muscle , and the neck extensor muscles . RESULTS Mean trapezius muscle activity was significantly higher in the older people ( 2.8%/3.7 % EMG(max ) for R/L ) compared to the young ( 1.1%/1.2 % EMG(max ) ) . There was a tendency to a higher activity in the older people for the deltoid muscle and the neck extensor muscles . There were small differences in shoulder muscle activation levels between mouse actions , target directions , and between precision dem and s. CONCLUSIONS Shoulder muscle activity during computer work is affected by age , but only to a minor extent by the type of computer mouse task . The deltoid and the trapezius muscle activities are low during computer mouse use when there is efficient forearm support by the table . Relevance An increasing number of people use computers for hours every day . Intensive use of computers increases the risk of development of work-related musculoskeletal symptoms in the shoulder region The present study evaluated the specific effects of motor dem and and visual dem and s on the ability to control motor output in terms of performance and muscle activation . Young and elderly subjects performed  multidirectional pointing tasks with the computer mouse . Three levels of mouse gain and three levels of target size were used . All subjects demonstrated a reduced working speed and hit rate at the highest mouse gain ( 1:8 ) when the target size was small . The young group had an optimum at mouse gain 1:4 . The elderly group was most sensitive to the combination of high mouse gain and small targets and thus , this age group should avoid this combination . Decreasing target sizes ( i.e. increasing visual dem and ) reduced performance in both groups despite that motor dem and was maintained constant . Therefore , it is recommended to avoid small screen objects and letters . Forearm muscle activity was only to a minor degree influenced by mouse gain ( and target sizes ) indicating that stability of the forearm/h and is of significance during computer mouse control . The study has implication s for ergonomists , pointing device manufacturers and software developers The aim was to investigate whether quantitative job dem and s influence muscle activity among women , and whether there are gender differences in duration of computer , mouse , and keyboard use and muscle activity of shoulder and forearm muscles during work . The study was carried out in an occupational setting , and 24 women and 11 men from a municipal administration participated . The duration of  computer , mouse , and keyboard use was measured by a commercial software package . Quantitative job dem and s were registered by question naire .  Electromyography ( EMG )  was measured bilaterally from the upper trapezius and the extensor digitorum communis muscles . No association was found between self-reported quantitative job dem and s and muscle activity among the women ( n=24 ) . The women used the keyboard more frequently ( p=0.020 ) and tended to perform fewer mouse clicks compared to men ( p=0.057 ) , but no difference was seen in EMG activity between men ( n=11 ) and women ( n=11 ) from the same department . However , office assistants ( six women ) showed significantly higher static EMG activity levels ( p=0.042 ) and almost significantly shorter EMG gap times ( p=0.060 ) than the rest of the subjects ( 5 women and 11 men ) . This indicated that shorter muscular resting periods among female office assistants as compared to the other subjects were due to differences in job content rather than gender differences Abstract . The overall aim of this study was to investigate whether time pressure and verbal provocation has any effect on physiological and psychological reactions during work with a  computer mouse . It was hypothesised that physiological reactions other than muscle activity ( i.e. wrist movements , forces applied to the computer mouse ) would not be affected when working under stressful conditions . Fifteen subjects ( 8 men and 7 women ) participated , performing a st and ardised text-editing task under stress and control conditions .  Blood pressure , heart rate , heart rate variability , electromyography , a force-sensing computer mouse and electrogoniometry  were used to assess the physiological reactions of the subjects . Mood ratings and ratings of perceived exertion were used to assess their psychological reactions . The  time pressure and verbal provocation  ( stress situation ) result ed in increased physiological and psychological reactions compared with the two control situations . Heart rate , blood pressure and muscle activity in the first dorsal interosseus , right extensor digitorum and right trapezius muscles were greater in the stress situation . The peak forces applied to the button of the computer mouse and wrist movements were also affected by condition . Whether the increases in the physiological reactions were due to stress or increased speed/productivity during the stress situation is discussed . In conclusion , work with a computer mouse under time pressure and verbal provocation ( stress conditions ) led to increased physiological and psychological reactions compared to control conditions Work-related upper extremity disorders ( WRUEDs ) that result from keyboarding  tasks are prevalent and costly . Although the precise mechanisms causing the disorder are not yet fully understood , several risk factors have been proposed . These include the repetitive nature of the motor task and the associated sustained static working postures , but also more psychological factors such as mental load . Epidemiological surveys have shown that WRUEDs are more prone to develop in the postural muscles of the neck/shoulder area than in the executive muscles controlling the h and . The present study investigated whether the activation patterns of these two muscle types are differentially affected by an additional mental load during the performance of a repetitive tapping task .  Participants tapped various keying patterns with their dominant index finger at two prescribed tempi . Mental load was manipulated by means of an auditory short-term memory task . We recorded the  EMG activity of two neck/shoulder muscles ( trapezius and deltoid ) , two upper arm muscles ( biceps and triceps ) , and four forearm muscles ( flexor digitorum superficialis , extensor digitorum , extensor carpi radialis longus and extensor carpi ulnaris ) and analyzed the kinematics and impact forces of the index finger . The results confirmed that the upper limb has two functions . Specifically , activity of the executive distal musculature was increased during tapping at the higher pace , while the activity of the postural upper limb musculature was elevated due to the memory task . We argue that continuously increased muscular activity can lead to fatigue and thus eventually cause musculoskeletal complaints . The results are discussed with respect to biomechanical adaptation strategies that deal with the consequences of increased noise in the neuromotor system due to enhanced mental processing The overall aim was to investigate the effect of psychosocial loads on trapezius muscle activity during computer keying work and during short and long breaks . In 12 female subjects ,  surface electromyography ( EMG ) was recorded bilaterally from the upper trapezius muscle during a st and ardized one h and keying task — interspaced with short ( 30 s ) and long ( 4 min ) breaks — in sessions with and without a combination of cognitive and emotional stressors . Adding psychosocial loads to the same physical work did not increase the activity of the trapezius muscle on either the keying or the control side , both of which remained at median and static EMG activity levels of around 5 % and 2.5 % of the maximal voluntary electrical activity ( EMGmax ) , respectively . The difference between the keying and the control side was significant ; and further the control side activity was significantly increased above resting level . During both short and long breaks , exposure to psychosocial loads also did not increase the activity of the trapezius muscle either on the side of the keying or the control h and . Of note is that during long breaks the muscle activity of the keying side as well as that of the control side remained at the same level as during the short breaks , which was increased above resting level . This was to be seen from the static and the median EMG activity levels as well as gap times , the overall mean values being : 0.4%EMGmax , 1.1%EMGmax , and 50 % in gap time , respectively . In conclusion : psychosocial loads are not solely responsible for increased non-postural muscle activity ; and increasing the duration of breaks does not per se cause muscle relaxation The influence of stress-induced muscle effort during computer utilization was tested in patients with repetitive strain injury ( RSI ) . Twenty academic research ers with a formal medical diagnosis of RSI and 20 matched controls , r and omly selected from a sample of 71 colleagues with and without RSI ,  typed after stress ( induced via an intelligence/skill task under social pressure ) and after relaxation . Results indicated that both groups had more electromyography ( EMG ) activity in the shoulder muscles during typing after stress than after relaxation , but that patients started with higher baseline muscle activity . Furthermore , EMG activity of different muscle groups during typing after stress correlated among controls , but not among patients . Finally , analysis of intake forms showed that patients scored higher than controls on neuroticism and alexithymia , but not on extraversion , openness , agreeableness and conscientiousness . It was concluded that deviations in muscle activity during computer utilization , as well as neuroticism and alexithymia , may be risk factors for RSI Computer-mouse work is characterized by repetitive movements combined with mental dem and s. The present purpose was to study how the body responded to simulated Computer Aided Design ( CAD ) work without memory dem and and when a high short-term memory dem and was introduced . Nine female subjects repetitively performed a task which involved 15 s of elevation of the right index and middle fingers followed by 6 s of rest . Every second time the fingers rested , the left index finger was required to type a six-figure number , either ‘ 123456 ’ ( without memory dem and ) or a r and om number shown half a minute before ( with memory dem and ) . After 7 min of performing the task without memory dem and , the memory dem and was introduced and continued for 1 h. Introduction of memory dem and result ed in increased heart rate ( 77 ← 84 beats/min ) , blood pressure ( systolic 129 ← 140 mmHg ; diastolic 72 ← 79 mmHg ) and forearm extensor muscle activity ( wrist , 2.7 ← 4.5 % EMGmax ; finger , 5.6 ← 7.5 % EMGmax ) and finger flexor muscle activity ( 0.7 1.2 % EMGmax ) indicating increased co-contraction . Hereafter , muscle activity and cardiovascular response tended to decrease . Self-reported stress and rating of perceived exertion ( RPE ) for the right shoulder increased throughout the period . Two additional sub- studies were inlcuded , which focused on adaptation to the physical load , showing a decrease in muscle activity and arousal , and re introduction of the memory load , showing a lower response as compared to the initial response . The practical consequences of the findings suggest that job content should have variable mental dem and 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 r and om 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 dem and compared to high mental workload . Heart rate and blood pressure seemed to respond similarly to high physical and mental workloads
target: In subgroup analyses , we found an equal effect of different stressor types ( i.e. cognitive/emotional stress , work pace , and precision ) on muscle activity in both body regions .
  In conclusion , simulated workplace stressors result in an increase in neck-shoulder and forearm muscle activity .
  No indications were found that different types of stressors affect these body regions differently .
background: Workplace stressors have been indicated to play a role in the development of neck and upper extremity pain possibly through an increase of sustained ( low-level ) muscle activity .
  The aim of this review was to study the effects of workplace stressors on muscle activity in the neck-shoulder and forearm muscles .
  An additional aim was to find out whether the muscles of the neck-shoulder and the forearm are affected differently by different types of workplace stressors .