Heart rate response to industrial work at different outdoor temperatures with or without temperature control system at the plant

Different outdoor temperatures, the association between indoor temperature control at the workplace and working heart rates of industrial employees were evaluated. The subjects, 6,016 male and female employees in 21 industrial plants in Israel, were screened for cardiovascular risk factors between 1985–87 (The CORDIS Study). The data collected included resting heart rate, working heart rate (based on one hour ambulatory ECG), outdoor temperatures, temperature control (TC) status of the plant, workload, age and health-related habits. At outdoor temperatures below or above 22–28°C, subjects working in plants with TC had lower mean working heart rate HR (- 2 bpm) than those working in plants without TC (p < 0·0004 after adjustment for confounders). No statistically significant differences in mean working HR were found between subjects working with TC (at all the outdoor temperatures) and those without TC within the outdoor temperature range 22–28°C. Based on working heart rate, indoor temperature control in industrial plants appears to moderate the cardiovascular strain in working subjects during both cold and hot days.     

Modelling energy expenditure during cycling

Nowadays, there is a strong trend to use cycling as a means of weight control or weight reduction by many weight-conscious people. These people are interested in knowing their caloric consumption while pedalling at some speed. Accurate measurements are possible through a laborious process of measuring oxygen consumption and carbon dioxide volume exhaled by using expensive equipment which requires skilled operators. However, accurate values are not crucial to the knowledge or health of weight-concerned people and estimated values should suffice this purpose. The estimation methods available in the literature contain some shortcomings. This paper presents a systematic methodology to estimate the caloric consumption while riding at submaximal levels, since near maximal levels are practiced by competitive cyclists only. The paper starts by enumerating and discussing the possible factors influencing the caloric uptake through a literature review. The most influential factors are used to develop a mathmatical model, based on experimental data, by using two approaches, i.e. multiple linear regression and linear programming. It is believed that the latter model fits the data better. Finally, an example is provided to show the utilization of the models.     

Estimation of energy expenditure in a work environment: Comparison of accelerometry and oxygen consumption/heart rate regression

The aim of this study was to compare estimation of energy expenditure (EE) in working environments, either from accelerometry or from an individual oxygen consumption/heart rate ([Vdot]O₂/HR) regression curve. The study participants were 46 volunteer workers aged 27±6 years old. A significant correlation between EE predicted by the [Vdot]O₂/HR curve and the accelerometer was observed (r=0.78, p <0.01). However, more disparities were observed between the two methods when the mean job intensity was not within 16% and 23% higher than resting HR. The accelerometer overestimated by a mean of 34.4% the prediction by [Vdot]O₂/HR regression if the intensity of the task was lower than a total of 1000 kcal/shift and underestimated the prediction by a mean of –24.9% if EE estimation of the work shift was higher than a total of 1500 kcal/shift. Despite a high correlation between both methods in the whole group, EE evaluated by accelerometry does not correspond to EE predicted by the [Vdot]O₂/HR regression curves when evaluated individually.     

Estimation of energy expenditure in a work environment: comparison of accelerometry and oxygen consumption/heart rate regression

The aim of this study was to compare estimation of energy expenditure (EE) in working environments, either from accelerometry or from an individual oxygen consumption/heart rate (VO(2)/HR) regression curve. The study participants were 46 volunteer workers aged 27+/-6 years old. A significant correlation between EE predicted by the VO(2)/HR curve and the accelerometer was observed (r=0.78, p <0.01). However, more disparities were observed between the two methods when the mean job intensity was not within 16% and 23% higher than resting HR. The accelerometer overestimated by a mean of 34.4% the prediction by VO(2)/HR regression if the intensity of the task was lower than a total of 1000 kcal/shift and underestimated the prediction by a mean of -24.9% if EE estimation of the work shift was higher than a total of 1500 kcal/shift. Despite a high correlation between both methods in the whole group, EE evaluated by accelerometry does not correspond to EE predicted by the VO(2)/HR regression curves when evaluated individually.     

Increasing surfboard volume reduces energy expenditure during paddling

Abstract

The purpose of this study was to investigate how altering surfboard volume (BV) affects energy expenditure during paddling. Twenty surfers paddled in a swim flume on five surfboards in random order twice. All surfboards varied only in thickness and ranged in BV from 28.4 to 37.4 L. Measurements of heart rate (HR), oxygen consumption (VO₂), pitch angle, roll angle and paddling cadence were measured. VO₂ and HR significantly decreased on thicker boards [VO₂: r = ?0.984, p = 0.003; HR: r = ?0.972, p = 0.006]. There was also a significant decrease in pitch and roll angles on thicker boards [Pitch: r = ?0.995, p < 0.001; Roll: r = ?0.911, p = 0.031]. Results from this study suggest that increasing BV reduces the metabolic cost of paddling as a result of lower pitch and roll angles, thus providing mechanical evidence for increased paddling efficiency on surfboards with more volume.

Practioner Summary: This study investigated the impact of surfboard volume on energy expenditure during paddling. Results from this study suggest that increasing surfboard volume reduces the metabolic cost of paddling as a result of lower pitch and roll angles, thus providing mechanical evidence for increased paddling efficiency on surfboards with more volume.     

Effects of load carriage on heart rate,blood pressure and energy expenditure in children

Fifteen male primary school children, aged 10 years, were selected to carry school bags of 10, 15 and 20% of their own body weights, where 0% body weight was used as a control. Maximum oxygen uptake ([Vdot]O₂max) tests were conducted on a motorized treadmill using a continuous incremental protocol. During the load carrying test, subjects walked on a treadmill at 1.1 m s^?1 for 20 min at each load condition. Blood pressures were measured before, immediately following, and at 3 and 5 min after every trial. Heart rate and expired [Vdot]O₂ were recorded before, during and 5 min after walking using a cardiopulmonary function system. The results showed a significant difference in oxygen uptake, energy expenditure and the recovery of blood pressure rise for between 10 and 20% body weight load conditions. The carrying weight of a school bag for children could be recommended as 10% of body weight because it was not significantly different from 0% load in the metabolic cost.     

Effects of load carriage on heart rate, blood pressure and energy expenditure in children

Fifteen male primary school children, aged 10 years, were selected to carry school bags of 10, 15 and 20% of their own body weights, where 0% body weight was used as a control. Maximum oxygen uptake (VO2max) tests were conducted on a motorized treadmill using a continuous incremental protocol. During the load carrying test, subjects walked on a treadmill at 1.1 m s(-1) for 20 min at each load condition. Blood pressures were measured before, immediately following, and at 3 and 5 min after every trial. Heart rate and expired VO2 were recorded before, during and 5 min after walking using a cardiopulmonary function system. The results showed a significant difference in oxygen uptake, energy expenditure and the recovery of blood pressure rise for between 10 and 20% body weight load conditions. The carrying weight of a school bag for children could be recommended as 10% of body weight because it was not significantly different from 0% load in the metabolic cost.     

Heart rate variability related to effort at work

Changes in autonomic nervous system function have been related to work stress induced increases in cardiovascular morbidity and mortality. Our purpose was to examine whether various heart rate variability (HRV) measures and new HRV-based relaxation measures are related to self-reported chronic work stress and daily emotions. The relaxation measures are based on neural network modelling of individual baseline heart rate and HRV information. Nineteen healthy hospital workers were studied during two work days during the same work period. Daytime, work time and night time heart rate, as well as physical activity were recorded. An effort–reward imbalance (ERI) questionnaire was used to assess chronic work stress. The emotions of stress, irritation and satisfaction were assessed six times during both days. Seventeen subjects had an ERI ratio over 1, indicating imbalance between effort and reward, that is, chronic work stress. Of the daily emotions, satisfaction was the predominant emotion. The daytime relaxation percentage was higher on Day 2 than on Day 1 (4 ± 6% vs. 2 ± 3%, p < 0.05) and the night time relaxation (43 ± 30%) was significantly higher than daytime or work time relaxation on the both Days. Chronic work stress correlated with the vagal activity index of HRV. However, effort at work had many HRV correlates: the higher the work effort the lower daytime HRV and relaxation time. Emotions at work were also correlated with work time (stress and satisfaction) and night time (irritation) HRV. These results indicate that daily emotions at work and chronic work stress, especially effort, is associated with cardiac autonomic function. Neural network modelling of individual heart rate and HRV information may provide additional information in stress research in field conditions.     

Relationship between maximum acceptable work time and physical workload

For safe job design, it is necessary to know the maximum acceptable work time (MAWT) for a given workload. The aim was to establish the relationship between MAWT and physical workload. Cycling tests at six different work rates relative to personal maximum working capacity were performed by 12 young adults in the laboratory. The oxygen uptake (VO₂) in the per cent maximum aerobic capacity (%VO_2max), relative heart rate (RHR) and relative oxygen uptake (RVO₂) were collected throughout the test. MAWT was determined by observing the heart rate data during the test. The results showed that MAWT was negatively correlated with %VO_2max, RHR and RVO₂(p<0.01). Three exponential regression models were obtained and all their R² >0.80. These models suggest that long-hour shifts (>10 h) should assign a lower work intensity than for an 8-h workday. It is also logical that the workload limit for a 4-h work shift could be set at about 10%VO_2max higher than the suggested limit for an 8-h workday.     

Relationship between maximum acceptable work time and physical workload

For safe job design, it is necessary to know the maximum acceptable work time (MAWT) for a given workload. The aim was to establish the relationship between MAWT and physical workload. Cycling tests at six different work rates relative to personal maximum working capacity were performed by 12 young adults in the laboratory. The oxygen uptake (VO(2)) in the per cent maximum aerobic capacity (%VO(2max)), relative heart rate (RHR) and relative oxygen uptake (RVO(2)) were collected throughout the test. MAWT was determined by observing the heart rate data during the test. The results showed that MAWT was negatively correlated with %VO(2max), RHR and RVO(2) (p < 0.01). Three exponential regression models were obtained and all their R(2) > 0.80. These models suggest that long-hour shifts (> 10 h) should assign a lower work intensity than for an 8-h workday. It is also logical that the workload limit for a 4-h work shift could be set at about 10% VO(2max) higher than the suggested limit for an 8-h workday.     

Relationship between phase and energy methods for disparity computation

The phase and energy methods for computing binocular disparity maps from stereograms are motivated differently, have different physiological relevances, and involve different computational steps. Nevertheless, we demonstrate that at the final stages where disparity values are made explicit, the simplest versions of the two methods are exactly equivalent. The equivalence also holds when the quadrature-pair construction in the energy method is replaced with a more physiologically plausible phase-averaging step. The equivalence fails, however, when the phase-difference receptive field model is replaced by the position-shift model. Additionally, intermediate results from the two methods are always quite distinct. In particular, the energy method generates a distributed disparity representation similar to that found in the visual cortex, while the phase method does not. Finally, more elaborate versions of the two methods are in general not equivalent. We also briefly compare these two methods with some other stereo models in the literature.     

Effect of different handgrip angles on work distribution during hand cycling at submaximal power levels

The effect of different handle angles on work distribution during hand cycling was determined. Able-bodied subjects performed hand cycling at 20% of maximum power level (mean (SD) power level: 90.0 (25.8) W) at a cadence of 70 rpm using handle angles of ±30°, ±15° and 0°. The handle angle had a significant effect on work during the pull down (p < 0.001) and lift up (p = 0.005) sector, whereby the highest work was performed with handle angles of +30° and ?15° respectively. The cycle sector had a significant effect on work (p < 0.001) and significantly (p = 0.002) higher work was performed in the pull down sector (25% higher than mean work over one cycle) as compared to the lift up sector (30% lower than mean work over one cycle). Therefore, a fixed handle angle of +30° is suggested to be optimal for power generation. The results of this study help to optimise the handbike–user interface. A more pronated handle angle compared to the one conventionally used was found to improve the performance of hand cycling and thereby the mobility of disabled people.     

Comparison of work rates, energy expenditure, and perceived exertion during a 1-h vacuuming task with a backpack vacuum cleaner and an upright vacuum cleaner

The purpose of this study was to evaluate two types of industrial vacuum cleaners, in terms of cleaning rates, energy expenditure, and perceived exertion. Twelve industrial cleaners (six males and six females, age 28-39 yr) performed two 1-h vacuuming tasks with an upright vacuum cleaner (UVC) and a backpack vacuum cleaner (BPVC). Measures for oxygen uptake (VO2) and ratings of perceived exertion (RPE) were collected continuously during the 1-h vacuuming tasks. Cleaning rates for the UVC and BPVC were 7.23 and 14.98 m2min(-1), respectively. On a separate day subjects performed a maximal treadmill exercise test to determine their maximal aerobic capacity (peak VO2). Average absolute energy costs (in Metabolic equivalents), relative energy costs of the vacuum task compared to the subjects' maximal aerobic capacity (% peak VO2), and RPE responses for the 1-h vacuuming tasks were similar between vacuum cleaners, but % peak VO2 and RPE values differed between genders. These results indicate that the BPVC was more efficient than the UVC. With the BPVC, experienced workers vacuumed at a cleaning rate 2.07 times greater than the UVC and had similar levels of energy expenditure and perceived effort, compared to the slower cleaning rate with the UVC.     

Relationship between satellite-derived land surface temperatures, arctic vegetation types, and NDVI

Arctic vegetation distribution is largely controlled by climate, particularly summer temperatures. Summer temperatures have been increasing in the Arctic and this trend is expected to continue. Arctic vegetation has been shown to change in response to increases in summer temperatures, which in turn affects arctic fauna, human communities and industries. An understanding of the relationship of existing plant communities to temperature is important in order to monitor change effectively. In addition, variation along existing climate gradients can help predict where and how vegetation changes may occur as climate warming continues. In this study we described the spatial relationship between satellite-derived land surface temperature (LST), circumpolar arctic vegetation, and normalized difference vegetation index (NDVI). LST, mapped as summer warmth index (SWI), accurately portrayed temperature gradients due to latitude, elevation and distance from the coast. The SWI maps also reflected NDVI patterns, though NDVI patterns were more complex due to the effects of lakes, different substrates and different-aged glacial surfaces. We found that for the whole Arctic, a 5 °C increase in SWI along the climate gradient corresponded to an increase in NDVI of approximately 0.07. This result supports and is of similar magnitude as temporal studies showing increases of arctic NDVI corresponding to increases in growing season temperatures over the length of the satellite record. The strongest positive relationship between NDVI and SWI occurred in partially vegetated and graminoid vegetation types. Recently deglaciated areas, areas with many water bodies, carbonate soil areas, and high mountains had lower NDVI values than predicted by SWI. Plant growth in these areas was limited by substrate factors as well as temperature, and thus is likely to respond less to climate warming than other areas.     

Postural load during VDU work: a comparison between various work postures

The aim of this study was to compare the postural load during VDU work in the following work postures: (1) Supporting and not supporting the forearms on the table top, (2) Sitting and standing positons, and (3) Sightline to the centre of the screen at an angle of 15 and 30 below the horizontal. The muscle load from the upper part of musculus trapezius and from the lumbar part of musculus erector spinae (L3 level) was measured by electromyography (EMG). Postural angles of head, upper arm and back were measured by inclinometers. The load on m. trapezius when using the keyboard was significantly less in sitting with supported forearms compared to sitting and standing without forearm support. Further, the time and number of periods when the trapezius load was below 1% MVC was significantly greater with support versus no support. The load on the right erector spinae lumbalis was also significantly less and the time when the load was below 1% MVC was significantly longer in a sitting work position with support versus standing without support. In addition, when using a mouse supporting the forearms reduced the static trapezius load in sitting. The results from this study document clearly the importance of giving the operator the possibility of supporting the forearms on the table top.     

Neck and shoulder muscle activity during work with different cash register systems

Levels of neck and shoulder myoelectric activity (EMG) were recorded in eight female cashiers during work with different cash register systems. Static, median and peak levels of load were determined, and comparisons were made between conventional keyboard operation and operation with horizontal scanner, vertical scanner and pen reader respectively, and between sitting and standing work postures. Each complete transaction (33 articles) lasted 74-166 s (mean 104 s). Cash register operation, regardless of register system, caused static load (mean) in the thoracic erector spinae at 4.1-6.2 TAMP% (Time-Averaged Myoelectrical Potential), in the infraspinatus at 2.9-5.8 TAMP%, and in the trapezius at 2.8-3.8 TAMP%. The cervical erector spinae and levator scapulae were very low in activity (0.6-1.3 TAMP% at the static load). Except for the left infraspinatus during scanner and pen reader operation, the median loads were low. Mean peak loads never exceeded 27.4 TAMP%. When the cashier was standing, the muscle activity at all levels of load was lower than when sitting, e.g., the left infraspinatus mean static load was 3.7 TAMP% (standing) and 5.4 TAMP% (sitting) (p less than or equal to 0.001). Differences were found between the cash register systems at median and peak loads. Work with scanners and pen reader caused, in ranking order, higher loads than conventional keyboard operation in the trapezius, infraspinatus and thoracic erector spinae. However, the main problem seems to be the repetitive handling of merchandise and the constant static load regardless of cash register system used.     

Posture variation among office workers when using different information and communication technologies at work and away from work

Office workers perform tasks using different information and communication technologies (ICT) involving various postures. Adequate variation in postures and muscle activity is generally believed to protect against musculoskeletal complaints, but insufficient information exists regarding the effect on postural variation of using different ICT. Thus, this study among office workers aimed to determine and compare postures and postural variation associated with using distinct types of ICT. Upper arm, head and trunk postures of 24 office workers were measured with the Physiometer® over a whole day in their natural work and away-from-work environments. Postural variation was quantified using two indices: APDF_(90-10) and EVA_(sd). Various ICT had different postural means and variation. Paper-based tasks had more non-neutral, yet also more variable postures. Electronics-based tasks had more neutral postures, with less postural variability. Tasks simultaneously using paper- and electronics-based ICT had least neutral and least variable postures. Tasks without ICT usually had the most posture variability. Interspersing tasks involving different ICT could increase overall exposure variation among office workers and may thus contribute to musculoskeletal risk reduction.     

Bicycle messengers: energy expenditure and exposure to air pollution

The purpose of the study was to determine the level of energy expenditure and exposure to air pollution for bicycle messengers. Relationships between heart rate (HR) and oxygen uptake, and between HR and pulmonary ventilation (VE) for each participant were established in laboratory tests. Air pollution and HR were measured during one working day. The total oxygen uptake was then described as the total energy expenditure in Joule (J) and in multiples of the energy expenditure at rest (MET). The mean energy expenditure during a working day (8 h) was 12 MJ, (4.8 MET). The level of air pollution exposure when cycling seemed to be comparable with the levels of exposure when sitting inside a vehicle. The VE during cycling was four times higher than resting value. Increased VE led to increased exposure to air pollution.     

Bicycle messengers: energy expenditure and exposure to air pollution

The purpose of the study was to determine the level of energy expenditure and exposure to air pollution for bicycle messengers. Relationships between heart rate (HR) and oxygen uptake, and between HR and pulmonary ventilation (VE) for each participant were established in laboratory tests. Air pollution and HR were measured during one working day. The total oxygen uptake was then described as the total energy expenditure in Joule (J) and in multiples of the energy expenditure at rest (MET). The mean energy expenditure during a working day (8 h) was 12 MJ, (4.8 MET). The level of air pollution exposure when cycling seemed to be comparable with the levels of exposure when sitting inside a vehicle. The VE during cycling was four times higher than resting value. Increased VE led to increased exposure to air pollution.     

Quantitative analysis of heart rate recovery profile during recovery from physical work

A mathematical model depicting a person's heart rate profile during the recovery period was developed. This model consisted of two heart rate parameters, namely, a resting heart rate (HRR) and a heart rate increase (ΓHR), and a model parameter (ß) representing the recovery rate of heart rate. A load-carrying experiment was conducted to study the following: (1) the relationship between work load and the recovery rate of heart rate, and (2) the possibility of using the model to estimate a person's heart rate recovery profile. From the experiment, heart rate recovery profiles from fourteen subjects were recorded and their recovery rates were determined. The results showed that for the load carrying activity the recovery rate of heart rate linearly correlated with work load; the higher the work load, the faster the recovery rate was. Furthermore, when comparing the heart rate recovery profiles estimated by the model to those previously recorded, remarkable similarities were found at every work load studied.