Effect of block weight on work demands and physical workload during masonry work

The effect of block weight on work demands and physical workload was determined for masons who laid sandstone building blocks over the course of a full work day. Three groups of five sandstone block masons participated. Each group worked with a different block weight: 11 kg, 14 kg or 16 kg. Productivity and durations of tasks and activities were assessed through real time observations at the work site. Energetic workload was also assessed through monitoring the heart rate and oxygen consumption at the work site. Spinal load of the low back was estimated by calculating the cumulated elastic energy stored in the lumbar spine using durations of activities and previous data on corresponding compression forces. Block weight had no effect on productivity, duration or frequency of tasks and activities, energetic workload or cumulative spinal load. Working with any of the block weights exceeded exposure guidelines for work demands and physical workload. This implies that, regardless of block weight in the range of 11 to 16 kg, mechanical lifting equipment or devices to adjust work height should be implemented to substantially lower the risk of low back injuries.     

The associations between psychosocial workload and mental health complaints in different age groups

The objective of the present study was to explore associations between psychosocial workload and mental health complaints in different age groups. A questionnaire was sent to 2021 employees of a Dutch railway company. Six aspects of psychosocial workload (work pressure, mental workload, emotional workload, autonomy, social support from colleagues and social support from supervisors) and three mental health outcomes (work-related fatigue, stress and burnout) were assessed. Associations between the aspects of psychosocial workload (distributed into tertiles) and health complaints were analysed by logistic regression analysis in four age groups (22–35, 36–45, 46–55 and 56–66 years old). In all age groups, worse work pressure was a significant risk factor for having mental health complaints. Worse emotional load in the younger employees and lack of social support in older employees were associated with a higher risk of having mental health complaints. Age-specific preventive measures should be implemented on both individual and group levels.

Statement of Relevance: With an ageing workforce, understanding relationships between age and work-related health ailments is increasingly important. This study found that emotional workload in younger and lack of social support in older employees were associated with a higher risk of mental health complaints. Work pressure was a risk factor in all age groups.     

Effects of different physical workload parameters on mental workload and performance

The design and evaluation of an occupational task should include an assessment of mental workload, since excessive levels of mental workload can cause errors or delayed information processing. Physically demanding work that is performed concurrently with a cognitive task may impact mental workload by impairing mental processing or decreasing performance. The primary objective of this study was to determine whether there is a differential effect of various types of physical activity on both mental workload and cognitive performance. Objective and subjective assessment tools (heart rate variability and visual analog scale) were used as indicators of mental workload, while correct responses during an arithmetic task reflected levels of performance. Thirty participants (ages 18-24 years) performed a combination of tasks inducing both physical and mental workload. Type of physical effort, frequency of movement, and force exertion level were manipulated to alter the workload associated with the physical activity. Changes in subjective ratings generally corresponded to changes in both performance on the arithmetic task and objective mental workload assessment. Some discrepancies occurred at the highest physical force exertion level as participants perceived an increase in effort to maintain the same level of performance. Further research is needed to determine the force exertion threshold, beyond which the physical effort required interferes with mental workload and/or cognitive performance.

Relevance to industry

Technological advancements have increased the requirement for many workers to execute cognitive tasks concurrently with physical activity. When designing and evaluating such situations it is important to determine the interactive effects of these activities. A simple, uni-dimensional tool is suggested as a screening tool to identify situations requiring excessive or increased mental workload that many degrade performance or place additional stress on the individual.     

Exoskeletons for industrial application and their potential effects on physical work load

The aim of this review was to provide an overview of assistive exoskeletons that have specifically been developed for industrial purposes and to assess the potential effect of these exoskeletons on reduction of physical loading on the body. The search resulted in 40 papers describing 26 different industrial exoskeletons, of which 19 were active (actuated) and 7 were passive (non-actuated). For 13 exoskeletons, the effect on physical loading has been evaluated, mainly in terms of muscle activity. All passive exoskeletons retrieved were aimed to support the low back. Ten-forty per cent reductions in back muscle activity during dynamic lifting and static holding have been reported. Both lower body, trunk and upper body regions could benefit from active exoskeletons. Muscle activity reductions up to 80% have been reported as an effect of active exoskeletons. Exoskeletons have the potential to considerably reduce the underlying factors associated with work-related musculoskeletal injury.

Practitioner Summary:

Worldwide, a significant interest in industrial exoskeletons does exist, but a lack of specific safety standards and several technical issues hinder mainstay practical use of exoskeletons in industry. Specific issues include discomfort (for passive and active exoskeletons), weight of device, alignment with human anatomy and kinematics, and detection of human intention to enable smooth movement (for active exoskeletons).     

The effect of sonification display pulse rate and reliability on operator trust and perceived workload during a simulated patient monitoring task

The present study investigated the effects of sonification pulse rate and sensor reliability on operator trust and mental workload. Processing resources and operator trust were sensitive to both pulse rate and sensor reliability. These findings suggest that setting pulse rates to 60 pulses per min may have considerable benefits in critical task environments.     

Effects of concurrent physical and mental demands for a short duration static task

The purpose of this study was to quantify the effects of concurrent physical and mental demands on the upper extremity muscle activity during static exertions. Seventeen healthy participants performed isometric upper extremity exertions at five levels of physical intensity (5%, 25%, 45%, 65%, and 85% maximum voluntary contraction (MVC)) in the presence and absence of a mental task (Stroop color word test). Muscular responses were quantified using surface electromyography (EMG) and motor performance was measured through force fluctuations. Subjective assessments were obtained through the NASA-TLX tool and the Borg CR-10 Scale. In general, a decrease in mean anterior and posterior deltoid muscle activity and co-contraction index (CCI) of the shoulder was observed in the presence of the mental task. However, these changes were more prominent at higher physical exertion levels compared to the lower levels. Furthermore, the additional mental task resulted in decreased upper and lower arm muscle activity, specifically at the 45% MVC level. Motor performance improved at the middle exertion levels, but was adversely affected by the mental task at higher exertion levels. Decreased motor performance at higher loads may have been a result of decreased muscular effort to maintain the loads in a steady posture. Both mental and physical demand adversely affected the NASA-TLX ratings, however, ratings using the Borg CR-10 Scale were only sensitive to changes in physical demand.

Relevance to industry

Workplace tasks, such as jobs performed by healthcare workers, assembly line workers, and computer operators, have become more multidimensional in the recent years; with workers experiencing combined physical and mental demands in their daily jobs, yet their effect on muscular responses is not clearly understood. Results from this study suggest that certain physical exertion levels are more susceptible to interference by mental demands than others.     

Using cerebral hemovelocity to measure workload during a spatialised auditory vigilance task in novice and experienced observers

This experiment was designed to assess cognitive load using transcranial Doppler sonography during the performance of a 40-min communication vigilance task in which messages were presented in different spatial locations or across a single monaural radio channel. In addition, some observers received 14 hours of practice to determine whether the neurophysiological measure was sensitive to a potential attenuation of workload. Critical messages were detected more frequently in the spatialised audio presentation mode condition, but there were no performance differences between experienced and novice observers. Neurophysiological data show that activation was greater in the novice condition than in the experienced condition, suggesting that novice observers expended greater effort. Furthermore, the neurophysiological measure showed more activation in the monaural radio condition than in the spatialised audio condition. The results support a resource account of vigilance and suggest that cerebral blood flow velocity can be used to diagnose the degree of attentional resource utilisation during vigilance tasks.

Practitioner Summary: Due to high workload experienced during vigilance tasks, displays and methods are sought which enhance performance. This study shows that spatialising auditory communications in a monitoring task enhances performance and attenuates mental workload. Also, experience mitigates excessive workload, and cerebral hemovelocity can be used to diagnose attentional resource utilisation.     

A study on the student pilot's mental workload due to personality types of both instructor and student

The main purpose of this paper is to provide the ideal flight crew combination for instructor and student pilots in order to enhance the flight training effects based on Myers Briggs Type Indicator (MBTI) theory. In addition to personality, various levels of flight difficulty are considered in order to investigate their potential interaction effect in terms of student pilots' mental workload measured in heart rate, altitude deviation, NASA-TLX (Task Load Index) and subjective degree of personality harmony. Based on an experiment performed in a real flight situation, we found significant effects of personality combinations in terms of all four outcome measures. Both group C types of instructors and students who are concrete, realistic and have mechanical skills turn out to be the ideal flight crew combination. A structural equation model, fitted to analyse causality among the four response variables, implied that as the heart rate increased, the altitude deviation increased. In addition, as the altitude deviation and personality harmony increased, NASA-TLX increased. The results of this study are expected to provide a theoretical basis for manning the flight crew combinations and thereby enhancing the efficiency of flight training.     

Impact of automated decision aids on performance,operator behaviour and workload in a simulated supervisory control task

In studies reporting automation effects on overall system performance and on the operator, the methods used to measure workload often did not appropriately reflect the complexity of this construct. The present study addresses the impact of automation on operator workload and behaviour in process control fault management. Workload effects were assessed with subjective, cardiovascular and secondary task performance indicators. Interactions with the interface of the process control simulation directed at gathering information and controlling the system were recorded. Automation made operators more efficient, allowing faster fault management with less information sampling and control actions. Subjective workload ratings were significantly lower in the assisted conditions as compared to manual, which was not reflected in cardiovascular and secondary task measures. Participants' information sampling activity did not differ between medium and high level of automation. Results suggest that participants paid constantly high attention to their task even with highly automated support.     

Cardiovascular and eye activity measures as indices for momentary changes in mental effort during simulated flight

This study examines effects of momentary changes in mental effort on cardiovascular and eye activity measures. A total of 19 male pilots performed an instrument flight task. Task load was manipulated by having the pilots perform flight manoeuvres of varying complexity. Multilevel analyses demonstrated clear effects of momentary changes in mental effort on both the cardiovascular and the eye activity measures. An increase in task load resulted in an increase of heart rate and a decrease in heart rate variability, mean dwell time and fixation duration. Heart rate differentiated between resting period and task execution. Heart rate variability from short data segments provided more insight in intermediate levels of mental effort. The eye activity measures were sensitive to intermediate levels of mental effort as well. Attitude changes resulted in an increase of mean dwell time and mean fixation duration. Task analysis is required to use eye measures as valid indices of mental effort. Having indications of the effects of changing mental demands during daily work of operators is of great importance nowadays. This paper presents an approach to estimate such effects on the basis of heart rate and eye activity measures. In particular, the use of averaged short-term heart rate variability measures is a relatively new aspect.     

Mental strain and annoyance during cognitive performance in different traffic noise conditions

In built-up areas, an increasing number of persons are affected by road traffic noise while performing mental work. This experimental study focused on annoyance and mental strain due to various noise scenarios. A total of 102 healthy, young persons (51 women, 51 men, aged 18–31 years) were randomly assigned to one of five experimental conditions determined by traffic flow (even, lumped) and traffic composition (20%, 40% heavy vehicles). While exposed to noise they performed a grammatical reasoning and a mathematical processing task. Performance and mental strain were not affected by any of the five noisy conditions. Individuals with high noise sensitivity were partially more annoyed and performed less than persons with low sensitivity.

Statement of Relevance: The present study provides information about mental strain due to tasks with different cognitive demands and the role of noise sensitivity in various traffic noise conditions. The results show that measures aiming at the reduction of the proportion of heavy vehicles should additionally consider particular traffic flow.     

Work tolerance and subjective responses to wearing protective clothing and respirators during physical work

This study examined work tolerance and subjective responses while performing two levels of work and wearing four types of protective ensembles. Nine males (mean age = 24·8 years, weight = 75·3 kg, [Vdot]O₂ max = 44·6 ml/kg min) each performed a series of eight experimental tests in random order, each lasting up to 180 min in duration. Work was performed on a motor-driven treadmill at a set walking speed and elevation which produced work intensities of either 30% or 60% of each subject's maximum aerobic capacity. Work/rest intervals were established based on anticipated SCBA refill requirements. Environmental temperature averaged 22·6°C and average relative humidity was 55%. The four protective ensembles were: a control ensemble consisting of light work clothing (CONTROL); light work clothing with an open circuit self-contained breathing apparatus (SCBA); firefighter's turnout gear with SCBA (FF); and chemical protective clothing with SCBA (CHEM). Test duration (tolerance time) was determined by physiological responses reaching a predetermined indicator of high stress or by a 180-min limit. Physiological and subjective measurements obtained every 2·5 min included: heart rate, skin temperature, rectal temperature, and subjective ratings of perceived exertion, thermal sensation, and perspiration.

The mean tolerance times were 155, 130, 26, and 73 min, respectively, for the CONTROL, SCBA, FF, and CHEM conditions during low intensity work; and 91, 23, 4, and 13 min, respectively, during high intensity work. Differences between ensemble and work intensity were significant FF and CHEM heart rate responses did not reach a steady state, and rose rapidly compared to CONTROL and SCBA values. SCBA heart rates remained approximately 15 beats higher than the CONTROL ensemble during the tests. At the low work intensity, mean skin.     

Work tolerance and subjective responses to wearing protective clothing and respirators during physical work

This study examined work tolerance and subjective responses while performing two levels of work and wearing four types of protective ensembles. Nine males (mean age = 24.8 years, weight = 75.3 kg, VO2 max = 44.6 ml/kg min) each performed a series of eight experimental tests in random order, each lasting up to 180 min in duration. Work was performed on a motor-driven treadmill at a set walking speed and elevation which produced work intensities of either 30% or 60% of each subject's maximum aerobic capacity. Work/rest intervals were established based on anticipated SCBA refill requirements. Environmental temperature averaged 22.6 degrees C and average relative humidity was 55%. The four protective ensembles were: a control ensemble consisting of light work clothing (CONTROL); light work clothing with an open circuit self-contained breathing apparatus (SCBA); firefighter's turnout gear with SCBA (FF); and chemical protective clothing with SCBA (CHEM). Test duration (tolerance time) was determined by physiological responses reaching a predetermined indicator of high stress or by a 180-min limit. Physiological and subjective measurements obtained every 2.5 min included: heart rate, skin temperature, rectal temperature, and subjective ratings of perceived exertion, thermal sensation, and perspiration. The mean tolerance times were 155, 130, 26, and 73 min, respectively, for the CONTROL, SCBA, FF, and CHEM conditions during low intensity work; and 91, 23, 4, and 13 min, respectively, during high intensity work. Differences between ensemble and work intensity were significant. FF and CHEM heart rate responses did not reach a steady state, and rose rapidly compared to CONTROL and SCBA values. SCBA heart rates remained approximately 15 beats higher than the CONTROL ensemble during the tests. At the low work intensity, mean skin temperatures at the end of the test were 32.7, 33.1, 36.7, and 36.3 degrees C, while mean core temperatures were 37.6, 37.9, 37.9, and 38.5 degrees C, respectively. The subjective data indicated that, in general, subjects were able to perceive relative degrees of physiologic strain under laboratory conditions. Wearing protective clothing and respirators results in significant and potentially dangerous thermoregulatory and cardiovascular stress to the wearer even at low work intensities in a neutral environment. Physiologically and subjectively, firefighter's turnout gear (the heaviest ensemble) produced the most stress, followed by the CHEM, SCBA, and CONTROL protective ensembles.     

An evaluation of a lane support system for bus rapid transit on narrow shoulders and the relation to bus driver mental workload

The use of dedicated bus shoulders is a key method for implementing bus rapid transit (BRT) in areas that do not have the space for additional infrastructure. However, the narrow width of the bus shoulder and the need to anticipate traffic hazards in the adjacent lane can both be significant stressors for bus drivers. Bus driver mental workload and stress in response to these conditions should be a significant concern both for operational safety and driver health.

This pilot study evaluated the potential stressors of traffic density and shoulder width in the context of an express BRT service in a large US metropolitan area. In addition, the study considered the potential role of a prototype lane support system (LSS) to support vehicle control within the narrow shoulder boundaries. Ten experienced bus drivers drove an actual route with an instrumented bus equipped with and without LSS. Self-reported effort was recorded along with performance measures of speed and position control relevant to mobility and safety objectives.

Bus drivers did note stressors in the BRT environment and the prototype LSS. However, the use of the shoulder during high-density traffic conditions did improve mobility. Moreover, the LSS did enhance safety on the shoulder when there was high-density traffic in the adjacent lane. However, there was no evidence that the LSS reduced bus driver workload while operating in the narrow shoulder. Future research should consider the impact of BRT operations and support systems on bus driver mental workload and stress, and support the deployment of such devices for bus operations on shoulders during high traffic volumes.     

Higher mental stimulation at work is associated with improved cognitive functioning in both young and older workers

The study examined whether mental stimulation received in the workplace positively affects cognitive functioning and rate of cognitive change. Data taken from the VISAT (ageing, health and work) longitudinal study concerned 3237 workers who were seen three times (in 1996, 2001 and 2006) and who were aged between 32 and 62 years at baseline. Measures of cognitive stimulation both at work and outside work were available at baseline. Cognitive efficiency was assessed on the three occasions through episodic verbal memory, attention and processing speed tests. Greater cognitive stimulation (at work and outside work) was associated with higher levels of cognitive functioning and a more favourable change over the 10-year follow-up. These results were obtained after adjustment for age, education, sex and a variety of medical, physical and psychosocial confounders. The study thus supports the hypothesis that exposure to jobs that are mentally demanding and that offer learning opportunities increases the level of cognitive functioning and possibly attenuates age-related decline.

Statement of Relevance: The effect of occupational activity on cognitive functioning is under-researched. This paper reports results from a substantive longitudinal study, with findings indicating that exposure to jobs that are mentally demanding are beneficial in increasing levels of cognitive functioning and possibly attenuating age-related decline.     

Team shared mental model as a contributing factor to team performance and students’ course satisfaction in blended courses

The purpose of the study was to examine how team shared mental model (SMM), team performance, and students’ course satisfaction change over time and how Team-SMM affects team performance and students’ course satisfaction. Forty-eight preservice teachers from two undergraduate blended courses participated in this study. The data were obtained via two online questionnaires (shared mental model instrument and Course Satisfaction Scale) administered throughout Spring 2010. Data analysis was conducted using repeated measures ANOVA and multiple linear regression techniques. Results indicated that Team-SMM and students’ course satisfaction changed slightly over time but the change was not statistically significant. Team performance increased significantly over the courses. Additionally, attitudes towards teammates and task were closely linked with effective team performance and students satisfaction. In the early stage of the courses, general team knowledge, resource, and environment explained a significant amount of variance in students’ course satisfaction.     

The effects of prior warning and lifting-induced fatigue on trunk muscle and postural responses to sudden loading during manual handling

This study investigated the effects of warning and lifting-induced fatigue on trunk muscle activity and postural responses to sudden loading. Thirty-one male subjects were subjected to sudden loading of a hand-held box with and without prior warning, before and after either lifting-induced fatigue or light callisthenic exercises. Results showed that warning did not alter the level of trunk muscle activity prior to sudden loading. Following warning, there was a reduction in all muscle and joint onset latencies and the magnitude of hip and knee flexion. Although fatigue did not influence muscle and joint initiation, it did negate the effects that warning had on reducing joint displacement. These findings indicate that warning prior to sudden loading may enhance postural responses, reduce ranges of joint motion and increase stability. However, the benefits of prior warning for reducing ranges of joint motion may not be present when a person is fatigued. Sudden unexpected loading and fatigue arising from manual handling practices in the workplace have been identified as contributing factors to the risk of low back injury. Findings from this study provide information that is important for the design of interventions intended to reduce the incidence of manual handling-related back injuries.     

Cardiorespiratory responses of firefighters to a computerized fire strategies and tactics drill during physical activity

Firefighters are subjected to a combination of physical and mental challenges in the course of their occupational responsibilities. However, due to the ecological factors involved with firefighting, it makes it extremely difficult to examine physiological and psychological changes that occur as a result of these combined challenges. The purpose of this study was to examine the efficacy of a computer-based Fire Strategies and Tactics Drill (FSTD) in eliciting psychological and physiological measures of stress in professional firefighters. In one session, participants exercised at 60% VO_2max for 37 min (exercise alone condition, EAC), and in the other session the firefighter exercised for an equal amount of time and responded to the FSTD (dual challenge condition; DCC) while exercising. Cardiorespiratory (heart rate [HR], respiration rate [RR], minute ventilation [V_E], oxygen consumption [VO₂], ventilatory efficiency [V_E/VO₂], and respiratory exchange ratio [RER]) and psychometric measures (State Anxiety Inventory [SAI] and Ratings of Perceived Exertion [RPE]) were obtained throughout the experimental protocols. The NASA Task Load Index was used to assess perceived physical and mental load during each condition. The results demonstrated that the participants perceived overall workload to be higher in the DCC. Repeated measures ANOVAs revealed no differences between the EAC and DCC for VO₂ or RER, but the DCC did elicit significantly greater elevations in HR, RR, V_E, and V_E/VO₂ compared to the EAC. These results suggest that the FSTD utilized in this study provides an effective method for examining the physiological and psychological responses of firefighters in a research laboratory environment.     

Reliability of physiological and subjective responses to physical and psychosocial exposures during a simulated manufacturing task

Responses to physical and psychosocial exposures can be measured using diverse methods, but their reliability, particularly under multiple exposures, is largely unknown. Five classes of methods were used to assess physiological and subjective responses among 24 participants to four combinations of physical and psychosocial exposures while performing two identical sessions of a simulated overhead manufacturing task. As an exploratory analysis, test–retest reliability was quantified using intraclass correlation coefficients (ICC) and coefficients of variation (CV). Discomfort ratings were reliable under less favorable exposures, and ratings of the psychosocial environment were most reliable under favorable social support. Workload ratings were most reliable with high physical exposure and favorable social support, and task performance was reliable overall. EMG and heart rate had relatively low reliability. Slightly less than half of the variables were considered reliable, but reliability depended on exposure conditions.Relevance to industry: The study provides information on the reliability of commonly used exposure measurement methods. The results can guide the selection of physiological and psychological work outcome measurements in future studies and work evaluations.