ORIGINAL ARTICLEJ. Wahlstro¨m Æ M. Hagberg Æ P.W. JohnsonJ. Svensson Æ D. RempelInfluence of time pressure and verbal provocation on physiologicaland psychological reactions during work with a computer mouseAccepted: 20 February 2002 / Published online: 22 May 2002 Springer-Verlag 2002Abstract The overall aim of this study was to investigatewhether time pressure and verbal provocation has anyeffect on physiological and psychological reactionsduring work with a computer mouse. It was hypothes-ised that physiological reactions other than muscle ac-tivity (i.e. wrist movements, forces applied to thecomputer mouse) would not be affected when workingunder stressful conditions. Fifteen subjects (8 men and 7women) participated, performing a standardised text-editing task under stress and control conditions. Bloodpressure, heart rate, heart rate variability, electromyog-raphy, a force-sensing computer mouse and electrog-oniometry were used to assess the physiologicalreactions of the subjects. Mood ratings and ratings ofperceived exertion were used to assess their psychologi-cal reactions. The time pressure and verbal provocation(stress situation) resulted in increased physiological andpsychological reactions compared with the two controlsituations. Heart rate, blood pressure and muscle ac-tivity in the first dorsal interosseus, right extensor digi-torum and right trapezius muscles were greater in thestress situation. The peak forces applied to the button ofthe computer mouse and wrist movements were alsoaffected by condition. Whether the increases in thephysiological reactions were due to stress or increasedspeed/productivity during the stress situation is dis-cussed. In conclusion, work with a computer mouseunder time pressure and verbal provocation (stressconditions) led to increased physiological and psycho-logical reactions compared to control conditions.Keywords Stress Æ Electromyography Æ Input device ÆVideo display terminal Æ Physiological reactionsIntroductionMusculoskeletal symptoms of the neck and upper ex-tremity associated with work with visual display units(VDUs) are common. In 1999, approximately 60% ofthe Swedish work force used a VDU in their profession (Statistics Sweden 2000), and it is believed that this fig-ure is increasing. It is thought that musculoskeletalsymptoms among VDU operators have a multi-factorialaetiology. Non-neutral wrist, arm and neck postures,workstation ergonomics, duration of computer workand psychological and social factors such as time pres-sure and high perceived work load, are believed to in-teract in the development of these symptoms (Bongerset al. 1993; Faucett and Rempel 1994).Experimental studies have shown that mental stresscan induce muscle activity (Ekberg et al. 1995; Larsson et al. 1995; Lundberg et al. 1994; Wærsted et al. 1991,1994; Wærsted and Westgaard 1996). In some of theseexperimental studies (Ekberg et al. 1995; Larsson et al.1995; Lundberg et al. 1994), authors have used theStroop Color Word Test (CWT) as a stressor, and theoutcome has primarily been muscle activity in the tra-pezius muscles. Other authors have used a complex two-choice reaction-time task (Wærsted and Westgaard1996; Wærsted et al. 1991, 1994) and focused on themuscle activity in the trapezius muscle, but also mea-sured muscle activity in other body regions. The CWTand the two-choice reaction-time task require minimalphysical activity during performance and are not easilytransferred to real work situations using a VDU or acomputer mouse.The aim of this study was to investigate whether timepressure and verbal provocation have any effect onEur J Appl Physiol (2002) 87: 257–263DOI 10.1007/s00421-002-0611-7J. Wahlstro¨m(&) Æ M. Hagberg Æ J. SvenssonDepartment of Occupational Medicine,Sahlgrenska University Hospital,St. Sigfridsgatan 85, 412 66, Go¨teborg, SwedenE-mail: [email protected]: +46-31-409728P.W. JohnsonDepartment of Environmental Health,University of Washington, Seattle, WA, USAD. RempelErgonomics Program, Division of Occupational Medicine,University of California, San Francisco, USAphysiological and psychological reactions when workingwith a computer mouse. It was also hypothesised thatphysiological reactions other than muscle activity (i.e.wrist movements, forces applied to the computer mouse)would not be affected when working under stressfulconditions.MethodsSubjectsFifteen subjects, 8 men and 7 women, volunteered to participate inthe study, which had been approved by the Ethics committee.Subjects from various occupations were recruited from theSahlgrenska University Hospital, Go¨teborg, and former fellowstudents of two of the authors (JS and JW). The mean age was30 years (range 18–48 years), the mean body mass index (BMI) was23.5 (range 20–28) and the median time with VDU work per weekwas 10 h (range 2–80 h). The subjects were all experienced com-puter mouse users and they all used their right hand to operate themouse. Prior to the study, subjects were given written and verbalinformation explaining the experimental procedures. None of thesubjects used medication for hypertension or any other cardio-vascular disease and they were all free of upper extremity muscu-loskeletal disorders, as determined by an interview.Experimental procedureAn adjustable VDU workstation was set up and the subjects ad-justed the table and chair to fit their personal preferences. AMacintosh computer with a 13-in (33 cm) colour display and astandard keyboard was used. Before the measurements, subjectspractised at the experimental workstation to familiarise themselveswith the equipment and the task.The subjects participated in a control situation (Control 1), astress situation (Stress) and, at the end of the experiment, a secondcontrol situation (Control 2). In the control situations, subjectsedited eight, five-line paragraphs of text (two pages) with no timeconstraints imposed. In each line, at a random location, one to fourcharacters were highlighted using coloured text. Subjects were in-structed to highlight the coloured characters with the computermouse and then delete the characters by hitting the delete key onthe keyboard with the hand operating the computer mouse. Ap-proximately 10–15 min later, in the stress situation, subjects wereasked to perform the same task but do twice the amount of work(edit four pages). Here, subjects were asked to work ‘‘as fast aspossible’’ and a time constraint of 40 s was imposed to