***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Thirty subjects were exposed to low frequency sinusoidal and r and om whole body vibration in the vertical direction , 0.3 m/sec2 ( rms ) . Changes in wakefulness during 15 min vibration were compared to changes occurring during corresponding pauses without exposure . Measurements were made on EEG and ECG . Exposure to whole body vibration was found to be correlated with reduction in wakefulness . This effect , verified by an increase of theta and decrease of alpha activity , was greater during sinusoidal than r and om vibration Objective This investigation was to assess the effect of different vibration frequencies on heart rate variability ( HRV ) and driving fatigue in healthy subjects during simulated driving , by the use of power spectrum analysis and subjective evaluation . Material s and methods Sixty healthy subjects ( 29.6±3.3 years ) were r and omly divided into three groups , A , B and C , and the subjects of each group participated in the simulated driving for 90 min with vertical sinusoidal vibration ( acceleration 0.05 g ) of 1.8 Hz ( group A ) , 6 Hz ( group B ) and no vibration ( group C ) , respectively . Low-frequency ( LF ) and high-frequency ( HF ) components of HRV , reflecting sympathetic and parasympathetic activities , and the LF : HF ratio , indicating sympathovagal balance , were measured throughout all periods . All indices of HRV were calculated in the pre-experiment period , mid-experiment period and end-experiment period , and were analyzed by repeated measures analysis of variance . Subjective responses to a question naire were obtained after the simulated task for the three groups . Results Significant differences in all indices of HRV were observed between different experiment periods and between any two groups . The ratings of subjective fatigue exhibited significant differences between any two groups . Conclusion The drivers ’ fatigue ratings were associated with vibration frequencies in simulated driving . The study quantitatively demonstrated that different effects on autonomic nerve activities were induced by different vibration frequencies We investigated the impact of mental fatigue on exploration in a complex computer task . The  exploration behavior of participants who underwent a fatigue manipulation ( N = 36 ) was compared with that of a  control ( nonfatigued ) group ( N = 32 ) . A distinction was also made between participants with high or low levels of general computer experience . Results showed that fatigued participants used significantly less systematic exploration and made more errors than did nonfatigued participants . Fatigued participants with low computer experience also showed significantly more rigid behavior than did the other participants . No differences were found on the number of subtasks solved . Compared with low-experience participants , highly experienced participants showed significantly more systematic exploration , less un systematic trial and error , solved more subtasks , and made fewer errors ( marginally significant p = .056 ) . Findings were interpreted as the result of reduced task engagement under fatigue and reduced involvement of executive control on behavior . Actual or potential applications of this research include guidelines to prevent detrimental effects of mental fatigue on exploration behavior OBJECTIVES Disability retirement may increase as the work force ages , but there is little information on factors associated with retirement because of disability . This is the first prospect i ve population -based study of predictors of disability retirement including information on workplace , socioeconomic , behavioral , and health-related factors . METHODS The subjects were 1038 Finnish men who were enrolled in the Kuopio Ischemic Heart Disease Risk Factor Study , who were 42 , 48 , 54 , or 60 years of age at the beginning of the study , and who participated in a 4-year follow-up medical examination . RESULTS Various job characteristics predicted disability retirement . Heavy work , work in uncomfortable positions , long workhours , noise at work , physical job strain , musculoskeletal strain , repetitive or continuous muscle strain , mental job strain , and job dissatisfaction were all significantly associated with the incidence of disability retirement . The ability to communicate with fellow workers and social support from supervisors tended to reduce the risk of disability retirement . The relationships persisted after control for socioeconomic factors , prevalent disease , and health behavior , which were also associated with disability retirement . CONCLUSIONS The strong associations found between workplace factors and the incidence of disability retirement link the problem of disability retirement to the problem of poor work conditions This study addressed the prevalence of working overtime in relation to psychosocial work characteristics and need for recovery . More precisely , the aim of this study was to find out ( 1 ) whether a relationship exists between working overtime and psychosocial work characteristics ( job dem and s and job control ) , ( 2a ) whether a relationship exists between working overtime and need for recovery , and finally ( 2b ) whether such a relationship depends on job type ( a specific combination of job dem and s and job control ) . The study sample ( N=1,473 ) consisted of a national r and om sample of office-based municipal administration employees who worked full-time . These employees completed a question naire on  working conditions , overtime and need for recovery  , among other things .  Overtime  was especially common in jobs characterised by high dem and s. The analyses showed that working overtime  is not associated with a higher need for recovery in the total study population . However , there was a positive relationship between overtime hours and need for recovery in high strain jobs ( high dem and s , low control ) . Furthermore , there was a positive relationship between structural overtime and need for recovery in active jobs ( high dem and s , high control ) . The relationship between overtime and need for recovery seems to be dependent upon working conditions ; indicators of overtime were associated with a higher need for recovery only for employees who experienced high job dem and s. Longitudinal research within a heterogeneous sample will be necessary to draw firm conclusions about causality with respect to the relationship between overtime , need for recovery and working conditions Study objective : To examine whether the effects of work stress on sickness absence vary by the level of control the employees have over their working times . Design : Prospect i ve cohort study . A survey of job strain , effort-reward imbalance , and control over daily working hours and days off was carried out in 2000–01 . The survey responses were linked with registered data on the number of medically certified ( > 3 days ) sickness absences from one year before the survey until the end of 2003 . The mean follow up period was 28.2 ( SD 8.1 ) months . Adjustments were made for demographics and behavioural health risks . Aggregated measures of worktime control according to workplaces were used to control for differences in reactivity and response style . Setting : Ten towns in Finl and . Participants : 16 139 public sector employees who had no medically certified sickness absences in the year preceding the survey . Main results : Among the women , individually measured control over daily working hours and days off moderated the association between work stress and sickness absence . The combination of high stress and good worktime control was associated with lower absence rates than a combination of high stress and poor worktime control . This finding was replicated in the analyses using workplace aggregates of worktime control . Among the men , the findings were less consistent and not replicable using aggregated measures of worktime control . Conclusions : Good control over working times reduces the adverse effect of work stress on sickness absence especially among female employees We investigated whether fatigue during prolonged exercise in uncompensable hot environments occurred at the same critical level of hyperthermia when the initial value and the rate of increase in body temperature are altered . To examine the effect of initial body temperature [ esophageal temperature ( Tes ) = 35.9 + /- 0.2 , 37.4 + /- 0 . 1 , or 38.2 + /- 0.1 ( SE ) degrees C induced by 30 min of water immersion ] , seven cyclists ( maximal O2 uptake = 5.1 + /- 0.1 l/min ) performed three r and omly assigned bouts of cycle ergometer exercise ( 60 % maximal O2 uptake ) in the heat ( 40 degrees C ) until volitional exhaustion . To determine the influence of rate of heat storage ( 0.10 vs. 0.05 degrees C/min induced by a water-perfused jacket ) , four cyclists performed two additional exercise bouts , starting with Tes of 37.0 degrees C. Despite different initial temperatures , all subjects fatigued at an identical level of hyperthermia ( Tes = 40 . 1 - 40.2 degrees C , muscle temperature = 40.7 - 40.9 degrees C , skin temperature = 37.0 - 37.2 degrees C ) and cardiovascular strain ( heart rate = 196 - 198 beats/min , cardiac output = 19.9 - 20.8 l/min ) . Time to exhaustion was inversely related to the initial body temperature : 63 + /- 3 , 46 + /- 3 , and 28 + /- 2 min with initial Tes of approximately 36 , 37 , and 38 degrees C , respectively ( all P < 0.05 ) . Similarly , with different rates of heat storage , all subjects reached exhaustion at similar Tes and muscle temperature ( 40.1 - 40.3 and 40 . 7 - 40.9 degrees C , respectively ) , but with significantly different skin temperature ( 38.4 + /- 0.4 vs. 35.6 + /- 0.2 degrees C during high vs. low rate of heat storage , respectively , P < 0.05 ) . Time to exhaustion was significantly shorter at the high than at the lower rate of heat storage ( 31 + /- 4 vs. 56 + /- 11 min , respectively , P < 0.05 ) . Increases in heart rate and reductions in stroke volume paralleled the rise in core temperature ( 36 - 40 degrees C ) , with skin blood flow plateauing at Tes of approximately 38 degrees C. These results demonstrate that high internal body temperature per se causes fatigue in trained subjects during prolonged exercise in uncompensable hot environments . Furthermore , time to exhaustion in hot environments is inversely related to the initial temperature and directly related to the rate of heat storage Daytime performance changes were examined during chronic sleep restriction or augmentation and following subsequent recovery sleep .  Sixty-six normal volunteers spent either 3 ( n = 18 ) , 5 ( n= 16 ) , 7 ( n = 16 ) , or 9 h ( n = 16 ) daily time in bed ( TIB ) for 7 days ( restriction/augmentation ) followed by 3 days with 8 h daily TIB ( recovery ) . In the 3-h group , speed ( mean and fastest 10 % of responses ) on the psychomotor vigilance task ( PVT ) declined , and PVT lapses ( reaction times greater than 500 ms ) increased steadily across the 7 days of sleep restriction . In the 7- and 5-h groups speed initially declined , then appeared to stabilize at a reduced level ; lapses were increased only in the 5-h group . In the 9-h group , speed and lapses remained at baseline levels . During recovery , PVT speed in the 7- and 5-h groups ( and lapses in the 5-h group ) remained at the stable , but reduced levels seen during the last days of the experimental phase , with no evidence of recovery . Speed and lapses in the 3-h group recovered rapidly following the first night of recovery sleep ; however , recovery was incomplete with speed and lapses stabilizing at a level comparable with the 7- and 5-h groups . Performance in the 9-h group remained at baseline levels during the recovery phase . These results suggest that the brain adapts to chronic sleep restriction . In mild to moderate sleep restriction this adaptation is sufficient to stabilize performance , although at a reduced level . These adaptive changes are hypothesized to restrict brain operational capacity and to persist for several days after normal sleep duration is restored , delaying recovery The effects of mental fatigue on planning and preparation for future actions were examined , using a task switching paradigm . Fatigue was induced by " time on task , " with subjects performing a switch task continuously for 2 hr . Subjects had to alternate between tasks on every second trial , so that a new task set was required on every second trial . Manipulations of response-stimulus intervals ( RSIs ) were used to examine whether subjects prepared themselves for the task change . Behavioral measurements , event-related potentials ( ERPs ) , and mood question naires were used to assess the effects of mental fatigue . Reaction times ( RTs ) were faster on trials in which no change in task set was required in comparison with switch trials , requiring a new task set . Long RSIs were used efficiently to prepare for the processing of subsequent stimuli . With increasing mental fatigue , preparation processes seemed to become less adequate and the number of errors increased . A clear poststimulus parietal negativity was observed on repetition trials , which reduced with time on task . This attention-related component was less pronounced in switch trials ; instead , ERPs elicited in switch trials showed a clear frontal negativity . This negativity was also diminished by time on task . ERP differences between repetition and switch trials became smaller with increasing time on task Abstract Objective : To examine the association between work stress , according to the job strain model and the effort-reward imbalance model , and the risk of death from cardiovascular disease . Design : Prospect i ve cohort study . Baseline examination in 1973 determined cases of cardiovascular disease , behavioural and biological risks , and stressful characteristics of work . Biological risks were measured at 5 year and 10 year follow up . Setting : Staff of a company in the metal industry in Finl and . Participants : 812 employees ( 545 men , 267 women ) who were free from cardiovascular diseases at baseline . Main outcome measure : Cardiovascular mortality 1973 - 2001 from the national mortality register . Results : Mean length of follow up was 25.6 years . After adjustment for age and sex , employees with high job strain , a combination of high dem and s at work and low job control , had a 2.2-fold ( 95 % confidence interval 1.2 to 4.2 ) cardiovascular mortality risk compared with their colleagues with low job strain . The corresponding risk ratio for employees with effort-reward imbalance ( low salary , lack of social approval , and few career opportunities relative to efforts required at work ) 
    Output:
    
RESULTS The drivers of fatigue with the greatest effect sizes include sleep deprivation and work environment factors such as noise , vibration , and temperature .
The most significant outcomes of fatigue include short-term cognitive and physical degradation and , to a lesser extent , error , injury , and illness .