Objectives

Physical and cognitive tasks occur together in many occupations. Previous reviews of combined tasks have mainly focused on their effects in a sports context. This review investigated to which extent combinations (concurrent or alternating) of occupationally relevant physical and cognitive tasks influence responses reflecting biomechanical exposure, stress, fatigue, performance, and well-being.

Methods

We searched Scopus, Pubmed, Cinahl, and Psychinfo for controlled experiments investigating the effects of combinations of occupationally relevant physical and cognitive tasks in participants aged 18 to 70. In total, we identified 12 447 records. We added recent papers that had cited these studies (n = 573) to arrive at a total of 13 020 publications. After screening for relevance, 61 studies remained, of which 57 were classified to be of medium or high quality. Of the 57 studies, 51 addressed concurrent tasks, 5 alternating tasks, and 1 both concurrent and alternating tasks.

Results

Most studies of concurrent physical and cognitive tasks reported negative effects, if numerically small, on indicators of biomechanical exposure, fatigue, and performance, compared to a physical task alone. Results were mixed for stress indicators, and well-being was too little studied to justify any conclusions. Effects depended on the tasks, including their intensity and complexity. Alternating physical and cognitive tasks did not appear to influence outcomes much, compared to having passive breaks in-between physical tasks.

Conclusions

The reviewed evidence indicated that concurrent physical and cognitive work tasks have negative, yet small effects on biomechanical indicators, fatigue and performance, compared to performing the physical task alone, but only if the physical task is intense, and the cognitive task is complex. Alternating between physical and cognitive tasks may have similar effects as breaking up physical tasks by passive breaks, but studies were few. Future studies should address ecologically valid combinations of physical and cognitive tasks, in particular in controlled field studies devoted to the long-term effects of combined work.

Pilots in long-duration flight missions in single-seat aircrafts may be affected by fatigue. This study determined associations between cognitive performance, emotions and physiological activation and deactivation – measured by heart rate variability – in a simulated 11-hours flight mission in the 39 Gripen aircraft. Eleven participants volunteered for the study. Perceived fatigue was measured by the Samn-Perelli Fatigue Index (SPFI). Cognitive performance and objective fatigue were measured by non-executive and executive tasks. Emotions were assessed by the Circumplex Affect Space instrument. Heart rate variability (HRV) was considered in relation to the cognitive battery test in four time points – Hours 3, 5, 7, 9 – and their associations with emotional ratings. Results indicated decrease in performance in the non-executive task after approximately seven hours. This result was correlated with self-reported measures of fatigue. Heart rate variability, assessed by indices of parasympathetic modulation – RMSSD, pNN50 and mean RR Interval – remained unchanged for both non-executive and executive tasks over time. There were associations between increased boredom as well as passiveness and decrease in stimulation as well as activeness, and increased HRV. This suggests that a low self-regulatory effort for maintaining performance in these tasks in these environmental conditions was required. Combined results indicate that pilots may be able to adapt to environmental demands and fatigue in long-duration missions providing that low self-regulatory effort is prevalent. Keywords: fatigue, heart rate variability, cognitive performance, emotions, long-duration military missions 

In occupational life, performing mental work tasks in-between fatiguing physical work tasks may allow recovery and reduce stress without losing productive working time. The temporal pattern of such alternations is likely a determinant of the recovery effect, influencing both stress and fatigue; the difficulty of the mental task would also be a likely determinant. The aim of this study was to determine to what extent the temporal pattern of alternations between a repetitive physical task and a cognitive task of different difficulties influenced perceived fatigability, performance fatigability, stress-related outcomes, and performance. Fifteen women performed four work sessions comprising 110 minutes of repeated bouts of a repetitive physical task (pipetting), alternating with a cognitive task (CT; n-back). Sessions differed in bout cycletime (short: 7+3 min vs long: 14+6 min) and CT difficulty (easy vs difficult). Fatigue was assessed from recordings of Maximal Voluntary Contraction (MVC) force in shoulder elevations and handgrip pre- and post- work, electromyography (EMG) from the right trapezius and right forearm extensors during work, and repeated self-ratings of fatigue and pain throughout the session. Stress was assessed using electrocardiography (heart rate variability), salivary alpha amylase, and self-reports. Perceived fatigue increased significantly over time for all protocols, and more in long-cycle than short-cycle conditions. EMG activity did not increase markedly over time in any condition. Neither objective nor subjective indicators suggested that stress increased over time, regardless of the temporal pattern. Pipetting performance remained stable in all conditions. Cognitive performance, measured as the proportion of correct and false answers, differed between CT difficulty levels, but remained stable over time, with no significant difference between temporal patterns. In summary, temporal patterns of alternating tasks influenced fatigue to some extent, but had no obvious influence on stress indicators or performance. Thus, alternating cognitive and physical work can serve as a feasible alternative to job rotation between physical tasks only.

Alternating between physical and cognitive tasks has been proposed as an alternative in job rotation, allowing workers to recover from the physical work while still being productive. However, effects of such alternations on stress have not been investigated. This controlled experiment aimed at determining the extent to which stress-related responses develop during alternating physical and cognitive work, and to determine the extent to which cognitive task (CT) difficulty influences these responses. Fifteen women performed three sessions of 10 consecutive work bouts each including a seven-minute repetitive physical task (pipetting) and a three-minute CT (n-back) at one of three difficulty levels. Stress was assessed in terms of changes in heart rate variability, blood pressure, salivary alpha-amylase, salivary cortisol, perceived stress, and cognitive performance. The work session did not result in any marked stress response, and CT difficulty did not significantly influence stress, apart from alpha-amylase being higher at the easiest CT (F = 5.34, p = 0.02). Thus, according to our results, alternating between repetitive physical tasks and cognitive tasks may be a feasible alternative to classic job rotation between physical tasks only, even if the cognitive task is quite difficult. Future studies should address possible effects of the temporal pattern of alternations, and combine even other occupationally relevant tasks, preferably for extended periods of time.

Objective: To determine the extent to which male and female office workers differ in their time-use composition of sitting behaviors (SB) and physical activity (PA) during work and leisure.

Methods: SB and PA was measured using thigh-worn accelerometers for up to 8 full days in 77 male and 104 female office workers. Daily time-use compositions during work and leisure were described in four exhaustive categories, i.e. sitting in short (<30  min) and long (≥30 min) bouts, standing, and active behaviors. Following a compositional data analysis procedure, isometric log-ratios (ilr) were calculated to express time in sitting relative to non-sitting, short relative to long sitting bouts, and standing relative to active behaviors. Differences between sexes (men and women) and domains (work and leisure) were examined on the basis of these ilrs using ANOVA.

Results: At work, time spent sitting in short bouts, long bouts, standing, and active was, on average, 34%, 36%, 22% and 8% among men and 31%, 37%, 24% and 8% among women. Corresponding proportions during leisure were 34%, 25%, 28% and 13% among men and 29%, 28%, 31% and 12% among women. Time spent sitting relative to non-sitting differed significantly between work and leisure (ilr sitting-vs-non-sitting, partial eta squared=0.09, p<0.01). During leisure, men used proportionally more time than women in short sitting bouts (ilr short-vs-long, partial eta squared=0.06, p<0.01) and spent more time in active behaviors relative to standing (ilr standing-vs-active, partial eta squared=0.04, p<0.01). No significant sex differences were observed during work (p>0.05).

Conclusions:  The leisure behavior observed among men is probably more beneficial for health than that observed for women. However, both men and women spent a major proportion of their time sitting, both at and outside their office work, and they were, in general, only little active. Thus, both men and women could benefit from interventions to reduce SB and increase PA both at work and during leisure.

The aims of this questionnaire study were to describe the occurrence and desired number of alternations between mental and physical tasks in industrial and non-industrial blue-collar work, and determine to which extent selected personal and occupational factors influence these conditions. On average, the 122 participating workers (55 females) reported to have close to four alternations per day between mental and physical tasks, and to desire more alternations than they actually had. They also expressed a general preference for performing a physical task after a mental task and vice versa. In univariate regression models, the desired change in task alternations was significantly associated with Gender, Age, Occupation, Years with current work tasks, and Perceived job control, while Occupation was the only significant determinant in a multiple regression model including all factors. Our results suggest that alternations between productive physical and mental tasks could be a viable option in future job rotation.

Background. Health and well-being at work is generally assumed to be associated with sufficient physical and mental variation. Job rotation, where workers typically alternate between different physical tasks, is a popular initiative. Controlled experiments suggest that favourable effects are associated with alternations between mental and physical tasks, but little is known about this intervention in real work. The aims of this study were (1) to describe the occurrence of alternations between mental and physical tasks, and (2) to identify key determinants of such alternations.

Method. We developed a questionnaire combining established questions with specific questions about alternations. Workers from two occupations (industrial and non-industrial blue-collar work), in jobs containing both physical and mental tasks, were included in the study. 122 (55 females) out of 293 workers approached at four companies answered the questionnaire.

Results. On average, the workers alternated 3.5 times per day between mental and physical tasks. In the non-industrial companies, workers reported wanting more alternations than they had, while desired and actual alternations did not differ in the industrial companies. This effect of occupation on the difference between the number of alternations wanted and the actual alternations available was significant (p < 0.001). Furthermore, there was a general preference for performing a physical task after a mental task, and vice versa. This main effect of primarily performed task type (i.e. either physical or mental) on preferred subsequent task type was significant (p < 0.001). In a univariate analysis, gender appeared to be a strong determinant of the occurrence of alternations, but the effect was absorbed when adding the occupation variable.

Discussion. Within the studied companies, work offered alternations between mental and physical tasks and there was a preference among workers to alternate between tasks. Occupation rather than gender was a key determinant of the number of alternations reported.

Purpose Most previous studies of concurrent physical and cognitive demands have addressed tasks of limited relevance to occupational work, and with dissociated physical and cognitive task components. This study investigated effects on muscle activity and heart rate variability of executing a repetitive occupational task with an added cognitive demand integral to correct task performance.

Methods Thirty-five healthy females performed 7.5 min of standardized repetitive pipetting work in a baseline condition and a concurrent cognitive condition involving a complex instruction for correct performance. Average levels and variabilities of electromyographic activities in the upper trapezius and extensor carpi radialis (ECR) muscles were compared between these two conditions. Heart rate and heart rate variability were also assessed to measure autonomic nervous system activation. Subjects also rated perceived fatigue in the neck–shoulder region, as well as exertion.

Results Concurrent cognitive demands increased trapezius muscle activity from 8.2 % of maximum voluntary exertion (MVE) in baseline to 9.0 % MVE (p = 0.0005), but did not significantly affect ECR muscle activity, heart rate, heart rate variability, perceived fatigue or exertion.

Conclusion Trapezius muscle activity increased by about 10 %, without any accompanying cardiovascular response to indicate increased sympathetic activation. We suggest this slight increase in trapezius muscle activity to be due to changed muscle activation patterns within or among shoulder muscles. The results suggest that it may be possible to introduce modest cognitive demands necessary for correct performance in repetitive precision work without any major physiological effects, at least in the short term.

Background

Aberration in autonomous nervous system regulation may play an important role in the development of work related musculoskeletal disorders (MSD). Recent studies indicated that sympathetic activity was increased relative to vagal effects in subjects with MSD, as measured through heart rate variability (HRV). However, the cause of this physiological change is difficult to determine, since several factors influence HRV, almost importantly the pattern of daily physical activity (PA).The aim of this study was to identify possible differences in PA between workers with and without MSD, and assess associations between HRV and PA. Methods: Twenty-six workers with MSD (41 years, 13 females) and twenty-four matched symptom-free controls from an industry in mid-Sweden participated in the study. ECG was monitored by the First Beat system whereas PA was recorded by a tri-axial accelerometer ActivPAL attached to thigh. GPS data were collected to identify the spatial location of the participants

Results

The groups showed similar distributions of total time spent at work, at home and "elsewhere". The lowest PA levels were found at work for both groups. Leisure time PA "elsewhere" was significantly lower among subjects with MSD than among controls. Time domain HRV variables were clearly correlated with PA levels and showed trend differences (0.05<p<0.1) between the MSD and the control group during sedentary and physically active periods.

Conclusions

Workers with MSD showed a different pattern of leisure time PA compared with symptom-free workers. These PA differences may have contributed in explaining the difference in autonomic activity, as measured through HRV, observed between the two groups, and even in previous studies of similar groups.

Background We determined the extent to which heart rate variability (HRV) responses to daily physical activity differ between subjects with and without chronic neck pain.

Method Twenty-nine subjects (13 women) with chronic neck pain and 27 age- and gender-matched healthy controls participated. Physical activity (accelerometry), HRV (heart rate monitor) and spatial location (Global Positioning System (GPS)) were recorded for 74 hours. GPS data were combined with a diary to identify periods of work, and of leisure at home and elsewhere. Time- and frequency-domain HRV indices were calculated, and stratified by period and activity type (lying/sitting, standing, or walking). ANCOVAs with multiple adjustments were used to disclose possible group differences in HRV.

Results The pain group showed a reduced HRV response to physical activity compared with controls (p=.001), according to the sympathetic-baroreceptor HRV index (LF/HF, ratio between low and high frequency power), even after adjustment for leisure time physical activity, work stress, sleep quality, mental health, and aerobic capacity (p=.02). The parasympathetic response to physical activity did not differ between groups.

Conclusions Relying on long-term monitoring of physical behavior and heart rate variability, we found an aberrant sympathetic-baroreceptor response to daily physical activity among subjects with chronic neck pain.