Energetic Workload Research Articles

Sensitivity analysis and validation of a genetic approach to enhance ergonomics in assembly lines

Manual assembly processes are largely performed today in the industry to benefit from human features of dexterity and flexibility. For this reason, the human factor should be properly regarded when designing assembly processes and systems, where repetitive and physically demanding operations are frequent. This work aims to present and validate a software tool for solving a bi-objective version of the assembly line balancing problem, in which, besides the efficiency of the process, the optimization of ergonomics is pursued. The software, based on a genetic algorithm, aims to distribute assembly tasks on the line to smooth the energetic workload among the different workers assigned to manual workstations, considering their physical capabilities and limits. To validate the system and assess its robustness, tests for different case studies taken from the industrial reality are presented and discussed, together with a sensitivity analysis conducted on problem parameters. Experimental results show that the developed tool optimizes the two objectives in different scenarios, thus demonstrating its profitable use in the industrial reality for planning manual assembly processes that do not overload workers assigned to the line.

Can breathing gases be analyzed without a mouth mask? Proof-of-concept and concurrent validity of a newly developed design with a mask-less headset

A portable headset has been developed to analyze breathing gases and establish the energetic workload of physically active workers. This proof-of-concept study aimed to investigate the following: (1) the validity of the headset compared to indirect calorimetry using a mouth mask; (2) the validity of the headset compared to the validity of oxygen consumption (V̇O2) estimated on the basis of heart rate; (3) the influence of wind on validity; and (4) user experiences of the headset. Fifteen subjects performed a submaximal cycling test twice, once with the headset, and once with a mouth mask and heartrate monitor. Concurrent validity of the headset was analyzed using an intraclass correlation coefficient (ICC). Across all phases, a good correlation between the headset and mouth mask was observed for V̇O2, carbon dioxide production (V̇CO2) and exhaled volume (V̇E) (ICC≥0.72). The headset tended to underestimate V̇O2, V̇CO2 and V̇E at low intensities and to overestimate it at higher intensities. The headset was more valid for estimating V̇O2 (ICC = 0.39) than estimates based on heart rate (ICC = 0.11) (n = 7). Wind flow caused an overestimation (md ≥ 18.4 ± 16.9%) and lowered the correlation of V̇O2 between the headset and the mouth mask to a moderate level (ICC = 0.48). The subjects preferred the headset over the mouth mask because it was more comfortable, did not hinder communication and had lower breathing resistance. The headset appears to be useable for monitoring development of the energetic workloads of physically active workers, being more valid than heart rate monitoring and more practical than indirect calorimetry with a mouth mask. Proof-of-concept was confirmed. Another design step and further validation studies are needed before implementation in the workplace.

PulseCath iVAC2L: next-generation Pulsatile Mechanical Circulatory Support

Contemporary state of the art percutaneous coronary intervention techniques offer treatment strategies and solutions to an increasing number of patients with heart failure and complex coronary artery disease. Percutaneous mechanical circulatory support is intended to alleviate the mechanical and energetic workload imposed to a failing ventricle by reducing left ventricle pressures and volumes and potentially also increasing coronary blood flow. The PulseCath iVAC2L is a transaortic left ventricular assist device that applies a pneumatic driving system to produce pulsatile forward flow. Herein, the essential aspects regarding iVAC2L are discussed with focus on its mechanisms of action and the available clinical experience.

Evaluation of team lifting on work demands, workload and workers' evaluation: An observational field study

The objective of this study was to assess differences in work demands, energetic workload and workers’ discomfort and physical effort in two regularly observable workdays in ironwork; one where loads up to 50kg were handled with two persons manually (T50) and one where loads up to 100kg were handled manually with four persons (T100). Differences between these typical workdays were assessed with an observational within-subject field study of 10 ironworkers. No significant differences were found for work demands, energetic workload or discomfort between T50 and T100 workdays. During team lifts, load mass exceeded 25kg per person in 57% (T50 workday) and 68% (T100 workday) of the lifts. Seven ironworkers rated team lifting with two persons as less physically demanding compared with lifting with four persons. When loads heavier than 25kg are lifted manually with a team, regulations of the maximum mass weight are frequently violated. Statement of relevanceLoads heavier than 25kg are frequently lifted during concrete reinforcement work and should be lifted by a team of persons. However, the field study showed that loads above 25kg are most of the time not lifted with the appropriate number of workers. Therefore, loads heavier than 25kg should be lifted mechanically.

An Integrated Mitochondrial ROS Production and Scavenging Model: Implications for Heart Failure

It has been observed experimentally that cells from failing hearts exhibit elevated levels of reactive oxygen species (ROS) upon increases in energetic workload. One proposed mechanism for this behavior is mitochondrial Ca2+ mismanagement that leads to depletion of ROS scavengers. Here, we present a computational model to test this hypothesis. Previously published models of ROS production and scavenging were combined and reparameterized to describe ROS regulation in the cellular environment. Extramitochondrial Ca2+ pulses were applied to simulate frequency-dependent changes in cytosolic Ca2+. Model results show that decreased mitochondrial Ca2+uptake due to mitochondrial Ca2+ uniporter inhibition (simulating Ru360) or elevated cytosolic Na+, as in heart failure, leads to a decreased supply of NADH and NADPH upon increasing cellular workload. Oxidation of NADPH leads to oxidation of glutathione (GSH) and increased mitochondrial ROS levels, validating the Ca2+ mismanagement hypothesis. The model goes on to predict that the ratio of steady-state [H2O2]m during 3Hz pacing to [H2O2]m at rest is highly sensitive to the size of the GSH pool. The largest relative increase in [H2O2]m in response to pacing is shown to occur when the total GSH and GSSG is close to 1 mM, whereas pool sizes below 0.9 mM result in high resting H2O2 levels, a quantitative prediction only possible with a computational model.

Evaluation of two working methods for screed floor layers on musculoskeletal complaints, work demands and workload

Screed floors are bound by sand–cement (SF) or by anhydrite (AF). Sand–cement floors are levelled manually and anhydrite floors are self-levelling and therefore differences in work demands and prevalences of musculoskeletal complaints might occur. The objective was to assess among SF layers and AF layers (1) the prevalence of musculoskeletal complaints and (2) the physical work demands, energetic workload, perceived workload and discomfort. A questionnaire survey and an observational field study were performed. Compared with AF layers (n = 35), SF layers (n = 203) had higher, however, not statistically significant different, prevalences of neck (20% vs. 7%), shoulder (27% vs. 13%), low back (39% vs. 26%) and ankles/feet (9% vs. 0%) complaints. Sand–cement-bound screed floor layers (n = 18) bent and kneeled significantly longer (Δ77 min and Δ94 min; respectively), whereas AF layers (n = 18) stood significantly longer (Δ60 min). The work demands of SF layers exceeded exposure criteria for low back and knee complaints and therefore new working measures should be developed and implemented. Practitioner Summary: In comparison with anhydrite-bound screed floor layers, sand–cement-bound screed floor layers exceeded exposure criteria for work-related low back and knee complaints. New working methods and measures for sand–cement-bound screed floor layers should be developed and implemented to reduce the risk for work-related musculoskeletal complaints.

The evaluation of team lifting on physical work demands and workload in ironworkers

Lifting and carrying heavy loads occur frequently among ironworkers and result in high prevalence and incidence rates of low back complaints, injuries and work-disability. From a health perspective, little information is available on the effect of team lifting on work demands and workload. Therefore, the objective of this study was to compare the effects of team lifting of maximally 50 kg by two ironworkers (T50) with team lifting of maximally 100 kg by four ironworkers (T100). This study combined a field and laboratory study with the following outcome measures: duration and frequency of tasks and activities, energetic workload, perceived discomfort and maximal compression forces (Fc peak) on the low back. The physical work demands and workload of an individual iron worker during manual handling of rebar materials of 100 kg with four workers did not differ from the manual handling of rebar materials of 50 kg with two workers, with the exception of low back discomfort and Fc peak. The biomechanical workload of the low back exceeded for both T50 and T100 the NIOSH threshold limit of 3400N. Therefore, mechanical transport or other effective design solutions should be considered to reduce the biomechanical workload of the low back and the accompanying health risks among iron workers.

Evaluation of the effect of a paver’s trolley on productivity, task demands, workload and local discomfort

The objective of this study was to determine the differences in the number of paving stones laid (productivity), task demands, energetic workload, body region discomfort and preference when laying paving stones with or without use of a paver’s trolley ( n = 8) in a within-subject controlled study of pavers. The number of paving stones laid and the task demands were measured by means of systematic observations at the workplace. The energetic workload was determined using the percentage of heart rate reserve (%HRR). Body region discomfort was measured using visual analog scales, and the workers’ preference was ascertained via interview. The use of a paver’s trolley had no effect on productivity, %HRR or body region discomfort compared to working without a paver’s trolley. The duration of knee-straining activities did not differ between working with (141 min) and without (146 min) the paver’s trolley. However, six of the eight pavers indicated that, given suitable circumstances, they wanted to use the paver’s trolley. Relevance to industry To reduce the chance of work-related low back and knee complaints among pavers, the duration, frequency and intensity of lower back and knee-straining activities should be limited by means of technical measures such as mechanical paving. The paver’s trolley does not appear to reduce knee-straining activities and therefore does not appear useful in reducing the risk of knee complaints and disorders.

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.

Workload of window cleaners using ladders differing in rung separation

The objective of the present study was to compare energetic workload, perceived exertion, perceived discomfort, safety, and mechanical load at lower limb joints among window cleaners during usage of extension ladders with 30 and 35 cm rung separation. Eleven healthy male professional window cleaners of short and tall stature participated in this study. No significant differences between 30 and 35 cm rung separation were observed for the energetic workload. Results concerning the perceived exertion, discomfort, and safety indicate that 35 cm rung separation is preferred. Based on the mechanical load at the hip, knee, and ankle during ascending and descending the ladder, 30 cm rung separation is preferable to 35 cm rung separation. It is advised to climb ladders with the knees inside the side rails of the ladder, but this seems only possible with 35 cm rung separation. Findings of the presents study suggest that overall, a 35 cm rung separation is marginally favourable while using extension ladders.

The physical demands upon (Dutch) fire-fighters in relation to the maximum acceptable energetic workload

The aim of this study was to assess the tasks and activities that make physical demands on Dutch fire-fighters and to compare them with a guideline related to the development of excessive fatigue. The occupational physical demands on Dutch fire-fighters were assessed by conducting a task analysis during 85 24-h shifts. While workplace observations on the duration and frequency of physical tasks and activities were recorded, the heart rate was measured. This was then used to calculate the heart rate reserve percentage (%HRR) for predefined working periods, tasks and activities during 24-h shifts. The findings indicate that actual fire-fighting during 24-h shifts is characterised by a low frequency of incidents, a short ‘turn-out’ time, short tasks, and activities with a moderate to occasionally high energetic workload. Two tasks which sometimes occur in actual fire-fighting exceeded the guideline on energetic workload. The conclusion was that, though the number of incidents and the occupational demands are low during 24-h shifts, the peak loads for these two tasks are energetically high and could lead to excessive fatigue. Consequently, attention may need to be paid to health surveillance for persons exposed to such energetic peak loads, the development of physical and medical selection procedures, training, and workplace adjustments.

Effect of the number of two-wheeled containers at a gathering point on the energetic workload and work efficiency in refuse collecting

The effect of the number of two-wheeled containers at a gathering point on the energetic workload and the work efficiency in refuse collecting was studied in order to design an optimal gathering point for two-wheeled containers. Three sizes of gathering points were investigated, i.e. with 2, 16 and 32 two-wheeled containers at a gathering point. The collecting of two-wheeled containers was simulated in a test circuit. The energetic workload was quantified by the parameters oxygen uptake (l min −1), heart rate (beats min −1) and perceived exertion. The work efficiency was quantified as the time it took to collect 32 two-wheeled containers per time period. The maximum acceptable amount of two-wheeled containers collected during an 8-h working day was estimated using the energetic criterion of a maximum oxygen uptake of 30% VO 2max. The size of the gathering point had no effect on the oxygen uptake, heart rate or perceived exertion. However, the number of two-wheeled containers per collecting period (work efficiency) and the maximum acceptable amount during an 8-h working day were higher in the conditions with 16 and 32 two-wheeled containers at a gathering point compared to the condition with the 2 two-wheeled containers at a gathering point.

Work situation and physical workload of refuse collectors in three different time periods

City officials from Haarlem, a Dutch city in which one of the first scientific studies on the workload of refuse collectors was performed, wanted to compare the work situation and physical workload in 1997 with the results of a study performed in Haarlem in 1985 and with the results of a national study conducted in 1993 . Depending on the results, they wanted to implement effective preventive measures. The present study consisted of a field study, a simulation experiment in the laboratory, and a questionnaire concerning work characteristics and health effects among 18 refuse collectors. The work situation and the energetic workload were not more favourable in Haarlem in 1997 compared to Haarlem of 1985 or the national study conducted in 1993. On several important parameters, such as the time carrying plastic bags or pushing containers, amount of refuse collected and percentage VO 2max during a working day, the results in the present study did not differ from those in earlier studies. However, the working postures and the perceived exertion of the refuse collectors in Haarlem in 1997 were more favourable when compared to the refuse collectors in the national study. The results have convinced the management to plan an intervention study of potentially effective measures to improve the work situation and to reduce the physical workload. Planned measures are the introduction of job rotation, an effective work–rest schedule and the redesign of two-wheeled containers. Relevance to industry This study shows that a comparison of the work situation and physical workload with former studies is an effective way to address the issue of preventive measures.

Effect of the Number of Two-Wheeled Containers at a Gathering Point on Energetic Workload and Work Efficiency

The effect of the number of two-wheeled containers at a gathering point on the energetic workload and the work efficiency in refuse collecting was studied. The results showed that the size of the gathering point had no effect on the energetic workload. However, the size of the gathering point had an effect on the work efficiency. This study shows that an increase in work efficiency does not directly imply an increase in workload.

Workplace factors and care seeking for low-back pain among female nursing personnel. MUSIC-Norrtälje Study Group.

Low-back pain is common among nursing personnel, and its origin is multifactorial. The present study focused on physical and psychosocial work load. The objectives of the study were to estimate the relative risk for nursing personnel, compared with other occupational groups, to seek health care for low-back pain, and to identify risk factors. This study is a part of a population-based case-referent study in the municipality of Norrtälje, situated north of Stockholm. Altogether 333 women served as cases and 733 served as referents. Eighty-one cases and 188 referents were employed in nursing work. The cases had sought health care for low-back pain during the study period, November 1993 to November 1996. The referents were randomly selected from the same population. The subjects filled out 2 questionnaires and participated in interviews about physical exposures and psychosocial factors. When the female nursing personnel were compared with other employed women, no increased risk of consultation for low-back pain was found. According to a multivariate logistic regression, nursing personnel exposed to forward-bending working positions, high energetic work load, perceived physical exertion, or insufficient social support had the highest risk estimates. In univariate analyses, the combination of physical and psychosocial risk factors was associated with a particularly high risk. In nursing work, physical load seems to be more significant than psychosocial factors when a worker seeks health care for low-back pain. The results of did not support the hypothesis that nursing work is a risk occupation for seeking care for low-back pain when compared with other occupations.

Bricklaying: a step by step approach to better work

Abstract This study concerns a development towards a feasible improvement in the working conditions of bricklayers. An occupational health survey showed that studies on the magnitude of workload were needed. These studies showed that the energetic workload was 35% for young bricklayers (25-35 years) and 41% for older bricklayers (45-55 years). The most effective improvement is diminishing this workload during the main task, which consumed 58% of the total worktime. An increase or decrease of the work pace had minor effects, but a heightened level of set out pile of bricks and barrel with mortar decreases the energetic workload significantly for the higher brick rows. The experienced workload and biomechanical back stress was also lowest for the higher rows and heightened set out bricks and mortar. Height-adjustable scaffoldings, which enable the bricklayer to put the bricks in the wall in an upright position, should be promoted. However, these cannot be used on a large scale and new equipment is now being developed for normal building sites. The implementation of the new working method will be thoroughly prepared in order to optimize its introduction on building sites.