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.     

The daily work load of refuse collectors working with three different collecting methods: a field study

The daily work load of 116 Dutch (male) refuse collectors working with polythene bags, two-wheeled mini-containers and large four-wheeled containers was studied. To this end a time analysis of the tasks and activities in the real working situation was made and the postures and the physiological work load of the collector working with the three different methods was assessed. Manual materials handling and the corresponding working postures were studied by means of observations. Heart rate (HR) was continuously recorded during the working day. Furthermore, to enable the assessment of the work load during refuse collecting as a percentage of the maximal oxygen uptake ([Vdot]O₂max) every refuse collectors' relationship between HR and oxygen uptake was measured during a simulation of the tasks and activities in the laboratory. The range in total working time of the refuse collectors was large. Most time is spent on the task ‘loading’; this lasted on average about 5?h. The mean number of handled objects for the three refuse collecting methods is 1500 bags, 500 mini-containers and 120 large containers respectively. The mean amount of collected refuse per collector of bags and mini-containers is about 11000kg. For the collectors of the large containers it is 27% higher, namely about 14000kg. The mean weight of one object for the bags, mini-container and large container is 7, 22 and 110?kg respectively. The straight posture was the most common in refuse collecting by bags. The posture flexed at the trunk and bent forwards or backwards occurred often while pushing and pulling containers. However, the refuse collectors of the large containers pushed and pulled for shorter periods during a working day in comparison with collectors of the mini-containers. Criteria for energetic overload were set at a mean energy expendiiure of 30% [Vdot]O₂ max and an energy expenditure of 50% [Vdot]O₂ max or more for a maximum of 60?min per day. According to these limits the energetic work load of the collectors of bags was indicated as being too high. In order to formulate guidelines in terms of mechanical and energetic load it is necessary to measure more accurately these loads during refuse collecting activities.     

The energy demands of portable gas analysis system carriage during walking and running

The aim of this study was to evaluate the carriage of a portable gas analyser during prolonged treadmill exercise at a variety of speeds. Ten male participants completed six trials at different speeds (4, 8 and 12 km h^? 1) for 40 min whilst wearing the analyser (P) or where the analyser was externally supported (L). Throughout each trial, respiratory gases, heart rate (HR), perceptions of effort and energy expenditure (EE) were measured. Significantly higher EE occurred during P12 (p = 0.01) than during L12 (855.3 ± 104.3; CI = 780.7–930.0 and 801.5 ± 82.2 kcal; CI = 742.7–860.3 kcal, respectively), but not at the other speeds; despite this, perceptions of effort and HR responses were unaffected. This additional EE is likely caused by alterations to posture which increase oxygen demand. The use of such systems is unlikely to affect low-intensity tasks, but researchers should use caution when interpreting data, particularly when exercise duration exceeds 30 min and laboratory-based analysers should be used where possible.     

The effect of a dynamic chair on seated energy expenditure

Abstract

Dynamic sitting approaches have been advocated to increase seated energy expenditure with the view of lessening the sedentary nature of the task. This study compared energy expenditure (EE) and overall body discomfort on a novel dynamic chair with a standard office chair. Fifteen pain-free participants completed a DVD viewing task on both chairs in a randomised order. Energy expenditure and discomfort were collected simultaneously. Linear mixed models were used to analyse steady-state EE recorded on each of the chairs. Differences in discomfort were analysed using Wilkoxon Signed Rank Tests. Sitting on the novel dynamic chair significantly (p = 0.005) increased energy expenditure compared to a standard office chair. The discomfort experienced was mild overall, but was significantly greater on the dynamic chair (p = 0.004). Whilst the EE was seen to be significantly higher on the dynamic chair, the MET values are still below 1.5 METS. Thus, the use of a dynamic chair does not seem to be the most effective measure to prevent sedentary behaviour.

Practitioner Summary: Sitting on a dynamic chair increased energy expenditure compared to sitting on a standard office chair among pain-free participants. Whilst the EE was seen to be significantly higher on the dynamic chair, the MET values are still below 1.5 METS (low level EE).     

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.     

Relationship between pulse rate and energy expenditure during graded work at different temperatures

Abstract

Pulse rate and energy expenditure were measured on fifteen male subjects who had been given ergometer cycling of ‘O’ and 32·6 W to 97·8 W in three temperatures of 22°C, 30°C, and 37°C. The variation in pulse rate of each graded work period was compared with the variation in energy expenditure for each environmental temperature. The pulse rate was significantly increased with the rise of environmental temperature (p << 0·01) whereas the energy expenditure (kJ min^?1) was consistently or effectively decreased with higher graded work. However, a correlation was obtained between the pulse rate and energy expenditure during graded work up to a limit of 150 beats min^?1, 160 beats min^?1, and 170 beats min^?1 in temperatures of 22°C, 30°C, and 37°C respectively. The results were analysed by computing the analysis of variance and regression equation evaluated for each temperature, indicating that independent regression lines having two components, one above 95 and other below 95 beats min^?1 were required in each set of temperature. The percentage error between observed and predicted values (pooled) or energy expenditure for the two ranges of pulse rates varied from 0·3 to 11·5 and from 0·5 to 9·5 respectively in the three temperatures.     

Physiological and perceptual responses to load-carrying in female subjects using internal and external frame backpacks.

Eleven female subjects (ages 18-33 years) walked on a motor-driven treadmill at 86 m/min for 1 h carrying 33% of their body weight in a backpack. The grade of the treadmill alternated every 15 min between 0 and 3%. Each subject carried an internal frame backpack for one trial and an external frame backpack for another trial on a separate day. The variables measured during the two load-carrying experiments included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (R), minute ventilation VE, and the ratings of perceived exertion for the chest (RPE-chest), shoulders (RPE-shoulders), and legs (RPE-legs). When oxygen uptake measured during load-carrying was expressed as a percentage of VO2max, the average values were 40.1% (63.5% HRmax) at 0% grade and 49.0% (69.6% HRmax) at 3% grade for both backpacks. No significant differences were found between the two packs for any of the metabolic, cardiorespiratory, or perceptual variables measured. Changes in treadmill grade had a significant effect on VO2, HR, and VE, regardless of the type of pack carried. Minute ventilation was the only physiological response to load-carrying that increased significantly as exercise duration increased. The values for RPE-chest, RPE-shoulders, and RPE-legs were significantly increased by both exercise time and treadmill slope, regardless of the type of pack frame carried. Thus despite relatively constant metabolic responses over time, increased perception of effort could compromise completion of the load-carrying task. It was concluded that differences in backpack frame design were not great enough to produce significant differences in the energy cost or perception of carrying a moderately heavy load on the back.     

Optimization of load carriage at desert environment

The present study was undertaken to assess the effect of different magnitudes of load on physiological responses of soldiers in desert terrain and also to estimate an optimum load that can be carried comfortably at specific walking speed. Nine infantry male soldiers of SHAPE-I standard with age 25.22 ± 1.02 years, height 170.78 ± 0.95 cm and weight 66.56 ± 2.38 Kg volunteered in this study. All participants were marched at speed of 6.13 ± 0.40 Km h⁻¹ in desert terrain with 10.7 Kg (16.07% BW) and 21.4 Kg (32.15% BW) load and without load. Heart rate (HR), respiratory frequency (RF), oxygen consumption (VO₂), minute ventilation (VE), energy expenditure (EE) and relative work load (RWL) were recorded by using K4b² system. During carrying of 10.7 Kg load HR, VO₂, EE, RF, VE and RWL (%VO₂max) were increased 13.88, 18.20, 20.16, 7.86, 19.30 and 23.71% respectively in comparison to no load. Similarly, during 21.4 Kg load, physiological responses viz.; HR, VO₂, EE, RF, VE and RWL (%VO₂max) were increased 24.84, 36.98, 33.68, 21.24, 38.25 and 40.64% respectively in comparison to no load. The observation of this study stated that 6.27 Kg (9.42%BW, 50% RWL), 13.7 Kg (20.58%BW, 60%RWL) and 24.86 Kg (37.35%BW, 75% RWL) can be recommended for 8 h, 2 h and for 30 min respectively.Relevance to industryMost of the countries do not have their own database for load carriage in specific environmental conditions. Result of this study will be helpful to the similar kind of population working under specified conditions.     

Energy Expenditure of Heavy Load Carriage

Abstract

Fourteen subjects (22 yr, 175 cm, 72 kg) walked for 20 min on a treadmill at 3-2, 4-8, or 64 km h^-1 carrying 35, 40, 45, or 50 kg; during a second phase, ten additional subjects (22 yr, 178 cm, 75 kg) attempted to walk for 45 min at the same speeds carrying 60, 65. or 70 kg Energy expenditure when expressed as cm³ oxygen per minute per kilogramme of total weight (man + clothing + load) agreed, for the no load condition, with literature values. After deducting the individual's no load cost, the resulting net energy expenditure for carrying the loads, when expressed as cm³ kg^-1 min^-1 was generally constant at each speed; i.e. loads from 35 to 70 kg showed no statistical differences in energy expenditure per kilogramme at 3 2 and 4 8 km h^-1. At 6-4 km h^-1 carrying 70 kg, the average measured cost per kg was statistically different (p < 005) than carrying 35 kg at this speed; subjects were working at greater than 90% of their maximal [Vdot]₀₂ levels carrying 70 kg. However. similar comparison of the measured cost per kg between loads of 40 and 65 kg was statistically the same at 6 4 km h^-1. The general constancy of measured energy expenditure per kg for loads even up to 70 kg, probably depends on the condition that the load is well balanced and close to the centre of the body. As reported earlier, higher costs are associated with loads in unbalanced positions. Thus, the limitations commonly encountered in load carrying capacity may arise from poor positioning of the load rather than from the weight of the load per     

Complete recovery time after exhaustion in high-intensity work

This study was aimed to investigate complete recovery time (CRT) after exhaustion in high-intensity work. Twenty-four subjects were divided into two groups based on the cardiorespiratory capability index, which was measured in a maximum capacity test. Each subject then performed two cycling tests (at 60% and 70% maximum working capacity). The subject continued cycling until exhaustion in each test and then sat recovering until he/she no longer felt fatigue or until the oxygen uptake (VO2) and heart rate (HR) returned to their baselines, whichever was longer. The results indicated that HR required the longest time to recover and, consequently, HR data were adopted to set the CRT. The CRT was significantly correlated with the cardiorespiratory capability index and the relative workload indices: RVO2 and RHR. The RVO2 was the average elevation in VO2 during work from the resting level as a percentage of maximum VO2 reserve. The RHR's definition was similar to that of RVO2. Based on the obtained CRT-prediction model, the CRT for a high-cardiorespiratory-capability person was 20.8, 22.1, 23.4, and 24.7 min at 50%, 60%, 70%, and 80% RHR levels, respectively. These suggested CRT values should be increased by 10 min for a low-cardiorespiratory-capability person.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO_2max) of 4.4 ± 0.3 l/min (mean ± SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter ‘rescued’ six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O₂ uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO_2max and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5–9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 ± 3 mmol/l. The peak oxygen uptake was 3.7 ± 0.5 l/min (84% of the VO_2max) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO_2max in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO_2max in absolute values and the working technique used. A minimum VO_2max of 4 l/min for firefighters was recommended.     

Development of a wrist-worn calorie monitoring system using bluetooth

Methods and tools for monitoring real-time human body information in daily life are required for advanced healthcare. In this study, a method for estimating energy expenditure during health exercises was evaluated and a wrist-worn sensing system based on the method was developed. Pulse monitoring was used to calculate energy expenditure by estimating oxygen uptake from a correlation between heart rate and oxygen uptake. Bluetooth technology was utilized for sending data by wireless communication. By the newly developed system, energy expenditure during exercise can be estimated considering individual difference and distinguishing changes in grade or load. Our goal is to construct a miniaturized wearable system that monitors vital signs and has many applications for healthcare. The study suggests that a wearable pulse sensing system proposed could provide useful information for healthcare.     

Physical workload of lorry drivers: a comparison of four methods of transport

Abstract

Four groups of eight lorry drivers, transporting goods on wheeled cages, as packed goods, on pallets, or as bulk cargo, were studied during a complete working day. The drivers working with bulk cargo served as a reference group. Manual materials handling and the working postures were studied by observation. The heart rate (HR) was continuously recorded and related to observed tasks. The relationship between HR and oxygen uptake during a simulation of loading and unloading and the maximal oxygen uptake ([Vdot]O2 max) were measured in a laboratory for every driver. The lorry drivers worked long hours, only the group transporting wheeled cages worked less than 11 hd^-1 on average. Driving made up almost half of the total working time in all groups. In general, the highest HR was found during loading and unloading. Loading and unloading of wheeled cages was done for 2nd^-1, at 50% of [Vdot]O2max. The drivers transporting packed goods and pallets loaded and unloaded for around 100mind^-1, at 48% and 35% of [Vdot]O2 max respectively. When the drivers of these two groups lifted, their trunks were flexed for more than 60% of the time. The most important difference between the reference group and the other groups was that the drivers of the former rarely pushed or pulled anything. It is suggested that the required pushing and pulling forces were largely responsible for the high physical workload during loading and unloading.     

The Cost of Work on a Vehicle Assembly Line

Abstract

The physiological cost of work on men working on a truck assembly line was measured. Twenty subjects took part in the study: all had their heart rates measured during work, leisure and sleep. Thirteen subjects had their oxygen consumption measured at work using a newly described respirometer (Miser). Results confirmed that such work may be classified as light industrial with an energy expenditure of 120-200 W

Mean heart rates during work were 91 ± SD 8 bt min^-1;, mean relative work load was 24 ± SD 4% and mean relative heart rates were 21 ± SD 7%. The mean of the ratios of work, sleep and leisure: sleep heart rates were 1 -45 ± SD 015 and 1-28 ± SD 012 respectively.     

Voluntary pacing and energy cost of off-road cycling and running

PURPOSE: The purposes of this study were (1) to compare self-chosen speed of off-road cyclists and runners on a hilly course, (2) to compare the energy expenditure of off-road cyclists and runners on the same terrain, and (3) to describe changes in energy expenditure over the course of the exercise period. METHODS: Runners and cyclists performed three laps on a 2.75 km gravel course in a single exercise bout. The course was divided into 13 segments differing in grade and length. Position on the course and heart rate were recorded every few seconds. Speed was computed for each course segment on each lap; energy expenditure was estimated using recorded heart rates and exercise-specific maximal oxygen uptake measurements made prior to participation in the study. RESULTS: There were significant relationships between grade and speed for both runners (r = 0.64) and cyclists (r = 0.44). The differences between cyclists and runners were greatest on downhill segments. Energy expenditure rates were not significantly different for runners (71.6% VO2 peak) and cyclists (68.5% VO2 peak). CONCLUSIONS: Off-road cycling and running are comparable in energy demands. Variation in skill levels may account for the increased variability in speed among cyclists on downhill terrain.     

The energetics of walking on sand and grass at various speeds

This study investigated the energetics of walking on sand and grass. Fourteen adult males, participated in the study. Participants had a mean age of 34.6 years old, 72.6 kg in mass and 172.5 cm in stature, who walked at 3, 4, 5, 6 and 7 km per h on sand and grass surfaces. Physiological measures included heart rate, O₂ uptake, CO₂ exhalation, ventilation and relative O₂ uptake using a MetaMax Ergospirometer. Speed was controlled in a methodology similar to the ‘Multistage 20-m Shuttle Run Test’. Data were collected during physiological steady rate at each determined speed. A minimum of 2 h rest was enforced between randomized conditions. Results indicate that there was a significant increase (p < 0.01) in all measured physiological indices indicative of energy expenditure when walking on sand compared to grass at 3–7 km per h, with the greatest disparity between the surfaces (ratio = 1.63) in relative O₂ consumption at 5 km per h.     

Woodlands equipment maintenance: An analysis of mechanical labor energy expenditure

The accident frequency rate of forestry field mechanics is eight times the industry average. A contributing factor is physical fatigue caused by energy-demanding tasks, difficult working positions, and hostile environmental conditions.

the heart rate/oxygen uptake method was used to determine human energy expenditure levels for eight specific maintenance activities. Eight work positions were also identified, and their energy expenditure levels were recorded.

Mean daily shift-level energy expenditures were found to be in excess of 10,000 kJ, equivalent to a continuous average output above 20.0 kJ per minute. The most energy-demanding task was removing engine protection plates. The most energy-demanding position was standing, with the body bent forward at the waist, over some obstacle.

It is concluded that maintenance mechanics routinely work at 33% of their predicted maximal oxygen uptake level, a value that is considered to be at the top of the acceptable range for physically active male workers. At this level, the potential for an accident situation is high.     

Reliability of the assessment of the oxygen/heart rate relationship during a workday

The purpose of the present study was to evaluate the reliability of the oxygen consumption/heart rate (VO(2)/HR) relationship used to estimate energy expenditure during a workday. Before and after a 6-10 h work shift, the VO(2)/HR relationship was measured in 57 workers (28 female, 29 male) in our laboratory. VO(2) was similar before and after the shift at HR of 100 and 125 beats per minute (bpm). However, the VO(2)/HR relation and perceived exertion (RPE) became less accurate after a work shift as VO(2) and RPE were, respectively, increased at HR above 150 and 125 bpm. Increase of RPE for a same exercise intensity was higher in female subjects. Our results suggest good reliability of the VO(2)/HR relationship at HR usually found in workplaces.     

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.     

Effect of load position on physiological and perceptual responses during load carriage with an internal frame backpack

The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10?min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO₂), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO₂, VE, and RPE were significantly lower in the high position (18.6?±?2.3?ml/kg/min, 31.7?±?5.0?l/min, 2.8?±?0.8, respectively) compared to the low position (22.2?±?3.0?ml/kg/min, 38.6?±?7.5?l/min, 3.7?±?1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8?±?16.8, 0.89?±?0.06, 30.3?±?4.2, respectively) to the low position (136.0?±?25.3, 0.92?±?0.04, 33.8?±?5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back.