An evaluation of physiological demands and comfort between the use of conventional and lightweight self-contained breathing apparatus.

The additional physiological strain associated with the use of self-contained breathing apparatus (SCBA) is mostly linked to the additional weight. Lightweight and conventional SCBA were assessed in a submaximal step test performed in full firekit (total weights 15 and 27 kg, respectively). Factors assessed were: comparative energy expenditure of the two sets, relationship between comparative energy expenditure and aerobic fitness and subjective discomfort. Measured variables were: oxygen consumption, heart rate, estimated VO2max and subjective discomfort (body part discomfort scale). The lightweight SCBA displayed a significant oxygen consumption benefit, which was independent of dynamic workrate and valued at 0.2561 min(-1). Mean heart rate responses were significantly lower with the light set. No relationship was found between comparative energy expenditure and aerobic fitness. The light set was rated as significantly more comfortable than the heavy. Further research is required to assess the extent of the energy consumption benefit in realistic fire suppression protocols and the contribution of ergonomic factors to the energy and comfort benefits.     

Energy expenditure of cycle rickshaw pullers in different places in India

The cycle rickshaw is a popular transportation device. The aim of the study was to assess workload of cycle rickshaw pullers–physiological and subjective at four different places in India. Subjects were instructed to pull a cycle rickshaw with two passengers, for 20 min. Working and recovery heart rates were recorded. The mean values of energy expenditure of pulling a cycle rickshaw varied from 23.5 ± 2.66 to 25.35 ± 1.51 kJ/min. Relative cardiac strain and cardiac cost indicated that the job is ‘heavy’ to ‘very heavy’. Subjective assessment of workload was ‘heavy’ to ‘very heavy’. The combined workload assessed from physiological parameters and subjective assessment indicated that the job could be categorised as ‘heavy’ to ‘very heavy’ at all the places studied and needs to be reduced by redesigning the structural and functional components of the cycle rickshaw. The rickshaw pullers carry out the jobs many times per day, sometimes without proper rest pauses between trips. The outcome of the research project is beneficial for cycle rickshaw pullers, health administrators as well as manufacturers of cycle rickshaws. Primarily, the manufacturers would be able to use the data for producing a newer model of cycle rickshaw, which would require less energy to drive. The health administrators would be able to take policy decisions for administering better health care for the unorganised and underprivileged workers. The pullers could be guided into taking care of their health by improving their work practice, i.e. taking a sufficient rest pause between trips.     

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.     

Blade size and weight effects in shovel design

The shovel is a basic tool that has undergone only nominal systematic design changes. Although previous studies found shovel-weight and blade-size effects of shovelling, the exact trade-off between the two has not been quantified. Energy expenditure, heart rate, ratings of perceived exertion and shovelling performance were measured on five subjects using five shovels with varying blade sizes and weights to move sand. Energy expenditure, normalised to subject weight and load handled, varied quadratically with the blade-size/shovel-weight (B/W) ratio. Minimum energy cost was at B/W = 0.0676 m2/kg, which for an average subject and average load would require an acceptable 5.16 kcal/min of energy expenditure. Subjects, through the ratings of perceived exertion, also strongly preferred the lighter shovels without regard to blade size. Too large a blade or too heavy a shovel increased energy expenditure beyond acceptable levels, while too small a blade reduced efficiency of the shovelling.     

The influence of flywheel weight and pedalling frequency on the biomechanics and physiological responses to bicycle exercise†

The physiological, subjective and biomechanical effects of altering flywheel weight and pedalling rate on a Quinton Model 870 bicycle ergometer were studied. Steel plates were added to the flywheel to increase its weight to 35·9 kg with a moment of inertia of 1·65 kg m². A 1·5 kg spoked wheel with a moment of inertia of 0·1 kg m² was used as the light flywheel. Eight subjects pedalled on two separate occasions for 6 min at 40, 50, 60, 70, 80 and 90 r.p.m. with workload levels representing 30 and 60% of their [Vdot]O₂max with each flywheel. Force plate pedals were used to measure the total resultant force on the pedals (F_R ) and the component perpendicular to the crank arm (F_T). A force effectiveness index (FEI) was denned as the average of F_T/F_R over a crank cycle. The result showed no statistically significant change (p<0·05) in [Vdot]O₂, heart rate and rating of perceived exertion of the FEI as a function of flywheel weight except for the [Vdot]O₂ at 50 r.p.m. for the light workload. As the r.p.m. increased from 40 to 90 r.p.m., the FEI decreased from 0·5 to 0·35 with the heavy load and from 0·36 to 0·22 with the light load. Measured physiological, subjective and biomechanical indices did not change significantly with flywheel weight. Increasing the pedalling rate caused a significantly less effective application of forces to the crank arm with only a small change in [Vdot]O₂.     

Maximum frequency acceptable to female workers for one-handed lifts in the horizontal plane

Abstract

A laboratory study was conducted to determine the maximum frequencies acceptable to female workers for one-handed lifts in the horizontal plane. A psychophysical method was used to determine maximum acceptable frequency for an 8-hour workday. Ten female college students were required to lift continuously three different loads to two different reach distances (38 and 63 cm) on a 91 cm high work table. The lifting task was paced by a repeating timer which the subject controlled according to her subjective feelings of fatigue. Heart rate and RPE were measured during the last 5min of the experiment to determine the physiological level of functioning and perceived exertion. Psychophysically determined maximum acceptable frequencies were compared with the standards based on methods-time measurement (MTM) analysis.

Statistical analysis showed that both the weight of the load and reach distance had a significant effect on maximum frequency acceptable to the subjects. No single value for percentage of maximum frequency can be used to establish permissible one-handed lift limits in women; rather, this value depends upon the weight of the object and distance of lift. The average maximum acceptable frequency was 51% of the maximum frequency that the subjects could maintain for a period of 4min. The subjects selected workloads which resulted in a mean heart rate of 101 beats/min. The subjects rated the perceived exertion ranging from ‘fairly light’ to ‘somewhat hard’. Performance based on MTM analysis ranged from 11% below to 32% above the maximum workload acceptable to the subjects. The non-significant heart rate differences found among the six load-distance combinations lend strong support for the use of psychophysical methodology in future studies of fatigue criteria. The study also supports the previous findings that separate physiological fatigue criteria are needed for tasks involving arm work and whole body exertion.     

Endurance time and physiological responses to prolonged arm lifting

The main objective of this study was to examine the effects of prolonged arm lifting tasks on endurance time and physiological responses. Ten male college students participated in the study. The independent variables were the frequency of handling and weight of load. The dependent variables were endurance time, oxygen consumption, minute ventilation, heart rate, and ratings of perceived exertion of the shoulder, arm, back, leg and overall body. The results indicated that: (1) endurance time decreased with an increase in frequency or load; (2) oxygen consumption and heart rate limits were dependent on the interaction of frequency and load; (3) oxygen consumption and heart rate limits for arm lifting were generally lower than limits for leg lifting tasks; and (4) for arm work, average physiological responses recorded over short durations were not significantly different from those based on long durations.     

A computerized system for measuring the effect of nursing care activities on the clinical indices of energy expenditure

A computerized system for measuring clinical indices of energy expenditure (heart rate, temperature and activity) was pilot tested on three low-birth-weight infants over a period of 24 hours. The mean heart rate was 163 beats/min and the following mean temperatures were recorded: heel, 34.7 degrees C; abdominal skin, 35.1 degrees C; incubator wall, 29 degrees C; and air, 25.5 degrees C. Activity, determined as the number of baseline crossings of the processed signal from a pressure mattress, was calculated to be 8-9 crossings/min. When compared with an established activity scale based on behavioral observation, a correlation of 0.84 was found. The system described is valid, reliable and interferes minimally with normal nursing activities.     

Distribution and determinants of maximal physical work capacity of Korean male metal workers

The distribution of maximal physical work capacity (MPWC) can be used to establish an upper limit for energy expenditure during work (EEwork). If physically demanding work has wearing effects, there will be a negative relationship between MPWC and workload. This study was conducted to investigate the distribution of MPWC among Korean metal workers and to examine the relationship between workload and MPWC. MPWC was estimated with a bicycle ergometer using a submaximal test. Energy expenditure was estimated by measuring heart rates during work. The study subjects were 507 male employees from several metal industries in Korea. They had a lower absolute VO_2max than the Caucasian populations described in previous studies. The older workers had a lower physical capacity and a greater overload at work. A negative relationship was found between MPWC and workload across all age groups. Upper limits for EEwork for all age groups and for older age groups are recommended based on the 5th percentile value of MPWC.     

OPTIMAL FORM AND DIMENSIONS OF HAND-GRIPS ON CERTAIN CONCRETE BUILDING BLOCKS

The optimal form and dimensions of hand-grips for handling certain types of concrete building blocks were found by theoretical considerations and laboratory experiments. Such grips wore found to reduce the physiological workload considerably. The maximal lifting power proved to be a far bettor criterion for the evaluation of minor changes in dimensions of handgrips than energy expenditure or heart rate during work.     

The Cost of Work in Medical Nursing

Abstract

The physiological cost of work was measured on the nursing staff of a general medical ward. Fourteen subjects took part in the study. Heart rates were measured during work and sleep on 13 nurses, and oxygen consumption measurements were made on 12, using the Miser Respirometer. In addition, maximum aerobic capacity was estimated on eight of the subjects

Mean heart rates during work were 93 ± SD 10 bt min^-1 significantly higher on the late than the early shift. The mean rate of energy expenditure was 147 ± SD 31 W. and was significantly higher in the morning than the afternoon or the evening

The mean relative work toad was 22% ± SD5%. The mean individual relative heart rate was 26% ± SD 9% and the mean ratio of work : sleep heart rates was 145 ± SDO-19 The findings placed medical nursing in the same category as light industrial work.     

Effect of safety shoes type,lifting frequency,and ambient temperature on subject's MAWL and physiological responses

ObjectiveThe purpose of this paper is to evaluate the lifting capabilities of individuals while wearing safety shoes in a hot environment and to investigate the behavior of the physiological responses induced by the lifting process associated with those variables.MethodsIn order to achieve the objectives of this research, two sequential studies were conducted. The first part was an acclimatization and training program followed by a psychophysical experiment. Seven male workers participated in this experiment from the university. A three-way repeated measures design, with three independent variables and seven response variables, was utilized in this study. The independent variables studied in the psychophysical experiment were: 1) environmental temperature (20 and 30 °C WBGT), 2) lifting frequency (1 and 5 lifts/min), and 3) safety shoes (light-duty, medium-duty and heavy-duty). The response variables for this experiment were: 1) maximum acceptable weight of lift (MAWL), 2) heart rate, 3) aural-canal temperature, 4) muscle electromyography (EMG) of four muscle groups (biceps brachii, anterior deltoid, trapezius, and erector spinae), 5) rating of perceived exertion, 6) rating of thermal sensation and7) safety shoes discomfort rating.ResultsThe psychophysical experiment results showed that the weights selected by participants at higher levels of the independent variables were significantly less than those selected at lower levels of the independent variables. Some of the interaction effects were also significant.ConclusionThis study found evidence that – in addition to lifting frequency, which is well reported in the literature – heat stress increases the workload intensity in manual lifting tasks influencing the psychophysical selection of MAWL and the physiological responses of the human body represented in aural-canal temperature, heart rate and muscular activities. The study findings demonstrated the necessity of accounting for work environmental temperature and type of worn safety shoes, which is a safety requirement by most employers, when calculating the recommended weight limits.Practitioner summaryMost of the manual materials handling studies had investigated worker's capacity to perform lifting tasks in different environmental conditions not considering the effect of wearing safety shoes. This research fills the gap by presenting safety guidelines regarding lifting tasks in a hot environment while wearing safety shoes.     

Effect of hypoxia,safety shoe type,and lifting frequency on cardiovascular and ventilation responses

ObjectiveThere is limited work on the physiological demands of lifting activities at different altitudes and different lifting frequencies when wearing different types of shoes. This study aimed to examine the heart rate variability (HRV) and ventilation responses of individuals in normobaric hypoxia (ambient oxygen of 15%, 18%, and 21%) while doing lifting tasks and wearing three types of different safety shoes (“light, medium, and heavy-duty”) at two different lifting frequencies (“1 lift/min and 4 lifts/min”).MethodsUsing an experimental study design, two sessions were conducted by ten male university students that included an acclimatization and training session followed by experimental lifting. The study used a four-way repeated measures design (4 independent and twenty-one responses, i.e., twelve HRV and nine ventilation responses).ResultsThe findings highlighted substantial low HRV and ventilation parameters for the light workload stress in the form of higher ambient oxygen content and lowered lifting frequency while wearing light safety shoe type. It also presented an increase in the physical demand, followed by increased lifting frequency and replication with increased mean heart rate and decreased mean RR, very low frequency (VLF) power, low frequency (LF) power, and low frequency to a high-frequency ratio (LF/HF).ConclusionOur findings suggest that if a safe lifting load limit is applied for workers in the industrial environment, the risk of musculoskeletal disorders will be mainly decreased, and the rate of production will be better with ambient oxygen content and appropriate safety shoes. This research would safeguard industrial workers' physical capacities and future health risks.     

Distribution and determinants of maximal physical work capacity of Korean male metal workers

The distribution of maximal physical work capacity (MPWC) can be used to establish an upper limit for energy expenditure during work (EEwork). If physically demanding work has wearing effects, there will be a negative relationship between MPWC and workload. This study was conducted to investigate the distribution of MPWC among Korean metal workers and to examine the relationship between workload and MPWC. MPWC was estimated with a bicycle ergometer using a submaximal test. Energy expenditure was estimated by measuring heart rates during work. The study subjects were 507 male employees from several metal industries in Korea. They had a lower absolute VO2max than the Caucasian populations described in previous studies. The older workers had a lower physical capacity and a greater overload at work. A negative relationship was found between MPWC and workload across all age groups. Upper limits for EEwork for all age groups and for older age groups are recommended based on the 5th percentile value of MPWC.     

Microgravity simulation: physical and psychological workload evaluation tests in an underwater environment

As weightlessness is not completely reproducible on Earth, usability evaluation of space systems is often simulated through tests in an aquatic environment. A Neutral Buoyancy Facility test programme was organized in a special pool to simulate Extra-Vehicular Activities on the Columbus module of the future International Space Station with the aim of assessing various aspects of crew interface design.This study was designed to evaluate workload using visibility, accessibility and operability tests. Diving workload was determined through basic physiological measurements, such as pulmonary ventilation and heart rate during underwater operations.As anxiety can influence physiological processes, and consequently also the workload evaluation determined through these parameters, we developed an evaluation methodology to investigate the anxiety level based on a specific questionnaire submitted to all subjects before and after the dives.Heart rate increased in underwater work to a value approximately 50% larger than the value obtained in the resting condition while sitting outside the pool. This increase in heart rate was accompanied by an increase in pulmonary ventilation of 200% larger than the value recorded in the rest condition while sitting outside the water. The extent of these increases was notable in all the test subjects, who varied in age and stature.Recorded values of workload, heart rate and pulmonary ventilation were evaluated on the basis of Christensen's (Arbeitsphysiol. 14 (1950) 251) and Wells’ (J. Appl. Physiol. 10 (1957) 51) classifications. Through this analysis it was possible to determine that the workload, indicated by performance on our neutral buoyancy tests, corresponds to moderate physiological work.For test subjects, anxiety related to underwater performance was light. Among the causes of anxiety all the subjects indicated the lack of confidence with neutral buoyancy tests and a feeling of lack of safety, typical of aquatic environments.We can conclude that context did not produce considerable psychological effects, and consequently that the psychological load did not influence heart rate and pulmonary ventilation values that can therefore be directly related to task workload.     

Psychophysiological responses in experienced firefighters undertaking repeated self-contained breathing apparatus tasks

In order to safely and effectively extinguish fires and rescue life, firefighters are required to routinely wear self-contained breathing apparatus (SCBA), yet little is known about the specific physiological and psychological demands associated with repeated exposure to tasks that require SCBA. A total of 12 experienced firefighters took part in a series of commonly encountered SCBA activities: free search, guideline search and live firefighting tasks under room temperature (～20°C) and extreme heat (～180°C) conditions to assess changes in heart rate, blood pressure, mood, perceived workload and air usage. Findings demonstrate that live firefighting is associated with greater perceived exhaustion than free search or guideline exercises; however, all tasks lead to high cardiovascular demand regardless of the presence of heat. No significant impact of task upon mood and no significant differences between the perceived demands of guideline, free search and live firefighting exercises were found.

Practitioner Summary: This study considered the physiological and psychological responses of firefighters undertaking SCBA exercises. Although live firefighting is associated with greater perceived exertion, the absence of differences in psychological domains between exercises demonstrates that task demands are not always dependent upon the presence of fire and that all tasks are mentally challenging.     

Physical Workload in Different Body Postures,While Working Near to,or Below Ground Level

The physical load of different working postures during a light job at low working level was compared while varying the frequency of forward movement and working level. The postures compared were bending, kneeling, squatting and sitting on a low stool. Energy expenditure, heart rate and the increase in heart rate over a five minutos' period were used as parameters. The following conclusions can be drawn. Bending and kneeling require less energy and arc less strenuous, when one hand (arm) is used as a support to balance the trunk. At high forward movement frequencies (more than 4 metres per minute or 5 movements per minute) the bending posture without arm support is loss strenuous than squatting and sitting on a one-legged stool. At low movements frequencies the squatting posture is preferable. Heart rate and energy consumption were slightly higher than that when sitting, but performance and also the gradient of the heart rate were slightly more favourable. The working height, varied from ? 14 cm to + 16 cm in comparison with the floor level, influenced the workload less. A remarkable increase in the work load was observed in the bending position only when the working level was lower than the level of the feet. If work has to be carried out in the ground itself, then squatting appears to be the most favourable position.     

Effect of strenuous live-fire drills on cardiovascular and psychological responses of recruit firefighters

The study examined the effects of repeated strenuous live-fire drills on cardiovascular and psychological responses of male recruit firefighters (n = 7). Participants performed three trials of a standardized set of tasks while inside a training structure containing several live fires. Measurements of heart rate, aortic blood flow, perceived exertion, respiratory and thermal distress, reaction time, and error rate were obtained before testing, after each trial and during recovery. Heart rate increased significantly during each of the trials, reaching age-predicted maximal values. Stroke volume was significantly lower after trial 3 versus trial 1 and prevalues. Perceived exertion, respiratory distress, and thermal distress all increased, indicating greater stress following firefighting activities. Reaction time and error rate did not change significantly, but there was a tendency for more errors following trials 2 and 3 versus trial 1. The training drills resulted in considerable physiological and psychological strain, which has the potential to impair cognitive function. Firefighters are encouraged to take all possible steps to mitigate the extent of the cardiovascular strain.     

Effect of strenuous live-fire drills on cardiovascular and psychological responses of recruit firefighters

The study examined the effects of repeated strenuous live-fire drills on cardiovascular and psychological responses of male recruit firefighters (n = 7). Participants performed three trials of a standardized set of tasks while inside a training structure containing several live fires. Measurements of heart rate, aortic blood flow, perceived exertion, respiratory and thermal distress, reaction time, and error rate were obtained before testing, after each trial and during recovery. Heart rate increased significantly during each of the trials, reaching age-predicted maximal values. Stroke volume was significantly lower after trial 3 versus trial 1 and prevalues. Perceived exertion, respiratory distress, and thermal distress all increased, indicating greater stress following firefighting activities. Reaction time and error rate did not change significantly, but there was a tendency for more errors following trials 2 and 3 versus trial 1. The training drills resulted in considerable physiological and psychological strain, which has the potential to impair cognitive function. Firefighters are encouraged to take all possible steps to mitigate the extent of the cardiovascular strain.     

Quantifying the physical intensity of construction workers,a mechanical energy approach

Construction workers typically undertake highly demanding physical tasks involving various types of stresses from awkward postures, using excessive force, highly repetitive actions, and excessive energy expenditure, which increases the likelihood of unsafe actions, productivity loss, and human errors. Biomechanical models have been developed to estimate joint loadings, which can help avoid strenuous physical exertion, potentially enhancing construction workforce productivity, safety, and well-being. However, the models used are mainly in 2D, or to predict static strength ignored their velocity and acceleration or using marker-based method for dynamic motion data collection. To address this issue, this paper proposes a novel framework for investigating the mechanical energy expenditure (MEE) of workers using a 3D biomechanical model based on computer vision-based techniques. Human 3D Pose Estimation algorithm based on 2D videos is applied to approximate the coordinates of human joints for working postures, and smart insoles are used to collect foot pressures and plantar accelerations, as input data for the biomechanical analyses. The results show a detailed MEE rate for the whole body, at which joints the maximum and minimum values were obtained to avoid excessive physical exertion. The proposed method can approximate the total daily MEE of construction tasks by summing the assumed cost of individual tasks (such as walking, lifting, and stooping), providing suggestions for the design of a daily workload that workers can sustain without developing cumulative fatigue.