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.     

Evaluation of metabolism from heart rate in industrial work

Oxygen consumption ([Vdot]O₂) and heart rate (HR) were measured in 40 men performing different types of industrial work in eight factories

A [Vdot]O₂-HR relationship was established for each subject using an exercise test on a bicycle ergometer. HR measured during the industrial work was entered in the [Vdot]O₂-HR function, and [Vdot]O₂ thus calculated. A systematic comparison of the calculated [Vdot]O₂ (c[Vdot]O₂) with the actual measured [Vdot]O₂ (m[Vdot]O₂), showed that c[Vdot]O₂ significantly overestimated the [Vdot]O₂ during industrial work. The degree of overestimation was related to the type of work performed. The static muscular activity and the non-steady-state characteristics of the work were responsible for most of the overestimation

A more reliable technique for estimating metabolic rate is to make simultaneous measurements of [Vdot]O₂ and HR at different times during the work day and then from these recordings establish a function: [Vdot]O₂=f(HR). Continuous HR recordings can then be used to calculate a more accurate estimate of the metabolic rate.     

Energy expenditure and clearing snow: a comparison of shovel and snow pusher

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400–600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption ([Vdot]O₂), pulmonary ventilation ( [Vdot]O_E), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, [Vdot]O_E, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (± SD) 141 ± 20bmin_-1 with the shovel, and 142 ± 19 beats-min_-1 with the snow pusher. [Vdot]O₂was 2·1 ± 0·41 min_-1 (63 ± 12% [Vdot]O₂max) in shovelling and 2·6 ± 0·51 min_-1 (75 ± 14% [Vdot]O₂max) in snow pushing (p< 0·001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.     

Metabolic,cardiovascular and spinal strain of a representative fuel replenishment task

The metabolic, cardiovascular and spinal strain of a representative fuel replenishment task for a tank crew were assessed using nine military subjects wearing coveralls in a comfortable ambient climate. The task involved lifting 5 gal jerry cans (weighing 23·4?kg) from the ground to a height representing a tank deck (1·676 m) at a rate of two lifts per minute for 15 min. Oxygen uptake ([Vdot]O₂), minute ventilation ([Vdot]E), heart rate (HR) and intra-abdominal pressure (IAP) were monitored continuously. After 15 min of lifting the mean [Vdot]O₂ was 0·821 min^?1 (S.D. 0·18). This was 27% of the predicted [Vdot]O₂ max. The mean [Vdot]E was 21·81 min^?1 (S.D.4·1) and the HR was 111·3 beats min^?1 (S.D. 17·8). The mean peak IAP was 105·6?mmHg, with 56% of the peak IAPs exceeding 90?Hg. The mean intrasubject coefficient of variation was 10·7% (range 7·2–24·2). In a separate series of 20 consecutive bimanual straight arm vertical lifts of 10?kg at 15 s intervals, the mean intrasubject COV% was 7·2% (range 3·2–11·2%). The replenishment task was considered acceptable in terms of the metabolic and cardiovascular strain. In terms of spinal strain, there may be an unacceptable risk of back injury if the task was normally undertaken as part of a soldier's full-time occupation over many years     

Energy cost and physiological responses of males snowshoeing with rotating and fixed toe-cord designs in powdered snow conditions

The purpose of this study was to measure the energy cost and physiological responses of males while snowshoeing with two separate toe-cord designs (rotating toe-cord system vs. fixed toe-cord design) in powdered snow conditions. Eight males snowshoed at self-selected intensity for two, 1600 m trials in two snowshoes, with a rotating toe-cord system and a fixed-toe cord design. It was found that heart rate (HR) (140 vs. 134 beats min^-1), oxygen consumption ([Vdot]O₂) (63.4 vs. 34.0 ml kg^-1min^-1), energy cost (56.0 vs. 52.4 kJ min^-1), and ratings of perceived exertion (RPE) (13 vs. 12) were significantly (p<0.05) higher while snowshoeing with the fixed toe-cord design than with the rotating toe-cord system. Snowshoeing with the rotating toe-cord system at an average speed of 3.96 km h^-1 produced mean &Vdot;O₂ values that were 56% of [Vdot]O₂ max, while snowshoeing with the fixed toe-cord design at 3.86 km h^-1 evoked mean [Vdot]O₂ values that were 60% of [Vdot]O₂ max. Mean HR while snowshoeing with the rotating toe-cord system was 70% of HR max, while the mean HR when snowshoeing with the fixed toe-cord design was 74% of HR max. These findings suggest that snowshoeing with a rotating toe-cord system results in lower cardiorespiratory strain in powdered snow conditions compared to snowshoeing with a fixed toe-cord design.     

The relationship between heart rate and oxygen uptake during non-steady state exercise

In this study the validity of using heart rate (HR) responses to estimate oxygen uptake ([Vdot]O₂) during varying non-steady state activities was investigated. Dynamic and static exercise engaging large and small muscle masses were studied in four different experiments. In the first experiment, 16 subjects performed an interval test on a cycle ergometer, and 12 subjects performed a field test consisting of various dynamic leg exercises. Simultaneous HR and [Vdot]O₂ measurements were made. Linear regression analyses revealed high correlations between HR and [Vdot]O₂ during both the interval test (r= 0.90±0.07) and the field test (r= 0.94±0.04). In the second experiment, 14 non-wheelchair-bound subjects performed both an interval wheelchair test on a motor driven treadmill, and a wheelchair field test consisting of dynamic and static arm exercise. Significant relationships were found for all subjects during both the interval test (r = 0.91±0.06) and the field test (r= 0.86±0.09). During non-steady state exercise using both arms and legs in a third experiment, contradictory results were found. For 11 of the 15 subjects who performed a field test consisting of various nursing tasks no significant relationship between HR and [Vdot]O₂ was found (r= 0.42±0.16). All tasks required almost the same physiological strain, which induced a small range in data points. In a fourth experiment, the influence of a small data range on the HR-[Vdot]O₂ relationship was investigated: five subjects performed a field test that involved both low and high physiological strain, non-steady state arm and leg exercise. Significant relationships were found for all subjects (r = 0.86±0.04). Although the r-values found in this study were less than under steady state conditions, it can be concluded that [Vdot]O₂ may be estimated from individual HR-[Vdot]O₂ regression lines during non-steady state exercise.     

Can accelerometry accurately predict the energy cost of uphill/downhill walking?

To evaluate whether an activity monitor based on body acceleration measurement can accurately assess the energy cost of the human locomotion, 12 subjects walked a combination of three diVerent speeds (preferred speed±1 km/h) and seven slopes (-15 to + 15% by steps of 5%) on a treadmill. Body accelerations were recorded using a triaxial accelerometer attached to the low back. The mean of the integral of the vector magnitude (norm) of the accelerations (mIAN) was calculated. [Vdot]O₂ was measured using continuous indirect calorimetry. When the results were separately analysed for each incline, mIAN was correlated to [Vdot]O₂ (average r = 0.87, p < 0.001, n = 36). [Vdot]O₂ was not significantly correlated to mIAN when data were globally analysed (n = 252). Large relative errors occurred when predicted [Vdot]O₂ (estimated from data of level walking) was compared with measured [Vdot]O₂ for different inclines (-53% at + 15% incline, to + 55% at -15% incline). It is concluded that without an external measurement of the slope, the standard method of analysis of body accelerations cannot accurately predict the energy cost of uphill or downhill walking.     

Comparison of three field methods for measuring oxygen consumption

The Oxylog (OX) and the Kofranyi-Michaelis ( KM) field methods for measuring oxygen consumption ( [Vdot]O₂) were compared with the conventional Douglas Bag (DB) technique in standardized walking and lifting work in the laboratory. Subjects comprised six men. According to the mean differences in [Vdot]O₂ the OX underestimated ( 41% and 6.4% ) and the KM overestimated (3.8% and 0.8% ) [Vdot]O₂in walking and lifting work, respectively. The linear regression equations between the DB and the OX as well as between the DB and the KM revealed a good agreement (r= 0.91-0.99) of the [Vdot]O₂values. The OX and the KM are accurate for reliable [Vdot]O₂measurements under field conditions. Some practical improvements for the OX use, based on several field studies, are recommended.     

The ‘Oxylog’: an evaluation

Abstract

The Oxylog is a portable instrument designed to measure the oxygen consumption ([Vdot]0₂) an ambulatory subject. Steady-state measurements have been made, using an Oxylog, of inspiratory volume ( [Vdot]₁) [Vdot]0₂ during bicycle ergometer exercise at work rates ranging from 30 to 150 W. These measurements have been compared with simultaneous measurements of expiratory volume ([Vdot] _E) and [Vdot]O₂ made using a dry gas meter and mass spectrometer.

Four experiments were conducted, during which a total of 433 comparative measurements were made. In two experiments the Oxylog significantly underestimated [Vdot]O₂ (by 4-4 and 5-6%). Averaging over the four experiments, however, the underestimate reduced to 1-5%, which could be accounted for by a respiratory exchange ratio of approximately 0-9. There was, overall, no significant difference between [Vdot] ₁ and [Vdot] _E.

It is concluded that the Oxylog is sufficiently accurate for the reliable determination of [Vdot]0₂ and of energy expenditure under field conditions.     

The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in dairy farming, using ambulatory heart rate and oxygen consumption measurements. The rate of perceived exertion was estimated with Borg scale. The maximal oxygen consumption was measured in the laboratory. The study group consisted of eight male and 15 female farmers. The handling of feed and manure was the heaviest work task in dairy farming. The aerobic capacity ([Vdot]O₂ max) of female farmers (26 ± 3 ml/min/kg) was below average, and their work required over 50% of [Vdot]0₂ max during most of the tasks. The [Vdot]0₂ max of male fanners (32±10 ml/min/kg) was moderate, and most work tasks required below 50% of [Vdot]0₂ max. The mean heart rate in dairy farming tasks was 99 beats min^-1 in men and 116 beats min^-1 in women. However, according to the rate of perceived exertion, the men experienced the same work tasks as subjectively more heavy than did the women. The physical strain of female farmers in dairy farming seems to be too high because of heavy work tasks and relatively low [Vdot]0₂ max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

The Aerobic and Anaerobic Components of Work during Submaximal Exercise on a Bicycle Ergometer

Abstract

Inter-subject variability of oxygen intake ([Vdot]O₂)n relation to the anaerobic component of work has been investigated intensely on two healthy subjects and extensively on two groups of young and older men during work on an upright, stationary bicycle ergometer.

Significant differences (p<0·001) in [Vdot]O₂ were shown to exist between the two groups of subjects and the healthy men at the higher work-loads which could not be eliminated entirely by correction for body weight. The residual variation of [Vdot]O₂ on work-load was shown to be a consequence of the variation of anaerobic component of exercise. During work on a bicycle ergometer at exercise above about 50% [Vdot] O₂ max this should be taken into account if a valid assessment of energy expenditure is to be made.     

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.     

Energy cost of backpacking in heavy boots

Previous studies have investigated the oxygen cost ([Vdot]0₂) of increasing boot weight during unloaded walking or running, and have shown that for each 100 g increase in weight of footwear there is a 0·7-1·0% increase in [Vdot]O₂ In reality (except in athletic events) the use of heavy footwear is associated with load carriage, usually backpacking. We therefore investigated the effects of increasing boot weight by 5% of body weight on the [Vdot]0₂ of backpacking a load amounting to 35% of the body-weight in five healthy young males who walked at 4·5 km/hour (0% grade) on a motor-driven treadmill. The results indicated a mean increase of 0·96% in [Vdot]0₂ whilst backpacking for each 100thinsp;-g increase in boot weight. In contrast the oxygen cost of increasing the backpack load was only 0·15% indicating that it was 6·4 times more expensive to carry weight on the feet as compared to the back. It is concluded that the relation between boot weight and oxygen cost, previously developed for unloaded walking and running, can reasonably be extended to include heavier boots and backpacking.     

Permissible loads based on energy expenditure measurements

The literature is reviewed and, based on this, it is suggested that the upper general tolerance limit over an 8-hour work day, consisting of mixed physical work, including handling operations, is approximately 30–35% [Vdot]O₂ max (on bicycle legwork or treadmill). Therefore, the individual tasks must be adjusted to a metabolic level not exceeding 30–35% [Vdot]O₂ max in the majority of the labour force or may be more realistic in specific groups within the labour force (young/ old, male/female). The following metabolic values are suggested (1 [Vdot]O₂ ): males <40 years: 0·7males>40 years: 0·6; females < 40 years: 0·6; females >40 years: 0·5. It is important to notice that even with a metabolic rate below 30–35% [Vdot]O₂ max it is possible that local overstrain and/ or fatigue in the back muscles during, for example, manual handling operations of long duration can occur     

Aerobic capacity of urban women homemakers in Bombay

Twenty-six healthy women homemakers residing in the metropolitan city of Bombay were studied on a treadmill and a cycle ergometer to determine their aerobic capacity ([Vdot]O₂ max) with a view to evaluating their cardio-respiratory fitness and ascertaining the job-demand-fitness-compatibility in household activities. The [Vdot]O₂ max was found to be significantly higher in treadmill experiments, i.e. 15% in absolute value and 18% in relative value, as compared with that obtained by cycle ergometry (p < 0·001). A much higher difference was observed in values derived from the two methods on the same subjects (i.e. 28% in absolute value and 31% in relative value). Thus, the [Vdot]O₂max obtained from treadmill experiments may be regarded as the maximal aerobic power or the highest oxygen uptake that an individual can attain during exercise, which in the sample of the present study was recorded as 1·901 min ^?1 (33·9 ml kg ^?1 min ^?1). The findings also revealed that age and body weight have a direct influence on [Vdot]O₂max, which was found to be significantly correlated, positively with the latter and negatively with the former (p<0·01 in both cases). The physiological job-demand of household activities seems to be compatible in relation to the [Vdot]O₂max of the homemakers.     

Interrelationships of respiratory variables of coal miners during work

Abstract

The respiratory responses of expiratory volume ([Vdot] _E), respiratory frequency (f _R), oxygen consumption ([Vdot] O₂), and carbon dioxide elimination ( [Vdot]CO₂) were measured for coal miners while they were performing a variety of work tasks (walking, carrying, shovelling, cranking and running). Because of the difficulties in relating the respiratory variables to external work rate and a close dependence of the respiratory responses on metabolic activity, oxygen consumption was chosen as an independent variable in the predictors for pulmonary ventilation, respiration frequency, and carbon dioxide elimination. It was necessary to use nonlinear equations for [Vdot] _E and [Vdot]Co₂ owing to exercise hyperpnoea above the anaerobic threshold.f _R did not correlate well with [Vdot]O₂ or any of the other respiratory variables. The relationship between [Vdot]_E and [Vdot]CO₂ was linear.     

Metabolic and respiratory profile of the upper limit for prolonged exercise in man

For high-intensity cycling, power (P) can be well described as a hyperbolic function of tolerable work duration (t): P=(W'/t) + P _LL W' is a constant and P _LL is the lower limit (asymptote) for P which is shown to occur at an O₂ uptake ([Vdot]O₂) lying above the estimated threshold for sustained blood [lactate] increase (Θ_Iac) but below the maximum [Vdot]O₂ ([Vdot]O₂max) obtained during incremental cycling. This relation suggests that, above P _LL, only a certain amount of work (W') can be accomplished regardless of its rate of performance, with [Vdot]O₂ max being attained at fatigue. Hence, P _LL defines a point of discontinuity in the [Vdot]O₂-P relation for supra-Θ_Iac exercise. In order to determine the factors responsible for the continued increase in [Vdot]O₂ (to the maximum fatiguing value) at power outputs >P _LL, we documented the temporal profiles of metabolic (rectal temperature; blood [lactate], [pyruvate], [norepinephrine], [epinephrine]) and respiratory ([Vdot]_E; [Vdot]O₂; [Vdot]CO₂; blood pH, PCO₂, [HCO₃ ^?]) responses to constant-load cycling in eight healthy males at P _LL (24 min) and slightly above P _LL (to exhaustion, i.e. < 24 min). [Vdot]O₂ manifested a delayed steady state at P _LL, despite catecholamine levels and core temperature continuing to increase throughout; blood [lactate] and pH plateaued, however. In contrast, [Vdot]O₂ continued to increase slowly for the duration of the exercise > P _LL and attained [Vdot]O₂max. The response patterns at P _LL, and > P _LL suggest that the slow phase of the [Vdot]O₂ response is best correlated with the temporal profile of blood [lactate], and hence the site and route of metabolism of this variable may play a major role in the [Vdot]O₂ kinetics for high-intensity exercise.     

Scheduling rest for consecutive light and heavy work loads under hot ambient conditions

Three male and three female heat-acclimated subjects participated in a series of five testing sessions aimed at validating a resting period which was assigned to follow work under warm-humid (T_db 36°C, T_wb 31°C) and hot-dry (T_db 50°C, T_wb 25°C) ambient conditions. Each working period consisted of 25 min of walking at 30% [Vdot]_o2max followed by five minutes of carrying a load uphill at 75% [Vdot]_o2max. The working period was based on the expected HR as it could be derived from: (1) the work-specific HR as determined from the linear relationship between % [Vdot]_o2max and HR; (2) the heat-induced increments in HR; and (3) the endurance limits imposed by the age-dependent HR_max. Each 30 min of work was followed by 30 min of rest either under the same ambient conditions as for the working period, or under neutral ambient conditions. Judged by the levelling off of HR and by setting the limits of the T_re rise to 38°C during the consecutive walking periods, only the resting under the neutral conditions proved adequate. The level of blood lactic acid was the same under all ambient conditions for each sex, but was higher for the males, who carried a load of 12 kg, as compared to 10 kg for the females.     

ERGONOMICS RESEARCH SOCIETY THE SOCIETY'S LECTURE, 1964.

Eight male volnntours, aged 20 to 43 yr, participated in a 1 min run to exhaustion. Six of the subjects had experienced work on the treadmill and ran regularly during the year. By means of a preliminary rim a work load was selected for each subject which would produce exhaustion in 60 sec. The speed of the treadmill was 12.8 kph for all runs except one (14.5 kph) and grade varied from 10 to 20%. The warm up consisted of walking 5.6 kph at a 10% grade for min and preceded the rim by 3 or 5 min. Oxygen consumption ([Vdot]o₂), heart rate (HR), and respiration rate (f) were recorded every 15 sec during the run and during the first 30 sec of recovery. Thereafter, recovory measurements were made during progressively longer intervals for a total of 30 min. [Vdot]0₃, during the run with warm up (2.69± 0.39 L) was significantly greater (p<0.05) than without warm up (2.50±0.41 L). Recovory [Vdot]o₃ and total [Vdot]o₂ (run plus recovory) were not significantly different between the warm up and without warm up runs. The results were not different when net [Vdot]o₂ ([Vdot]o₂minus rest [Vdot]o₃) was compared. A significant increase in heart rate was achieved during rutis with warm up compared to no warm up. Respiration rates were also increased with warm up but not significantly. The conclusion was that under the conditions of this study, warm up is of energetic benefit in preparing for a short exhaustive run.     

Physiological factors affecting upper body aerobic exercise

This study examined the influence selected physiological measurements have upon peak oxygen uptake (peak [Vdot]O₂) elicited by upper body (arm crank) exercise employing crank rates of 30 and 70 r.p.m. Nine male volunteers completed: two maximal effort arm crank tests, one cycle exercise maximal aerobic power (AP) test, measurements of isokinetic elbow extension strength (ES), isometric grip strength (GS) and arm volume (AV). Partial correlation coefficients (R) were obtained from a multiple regression analysis. For the 30 r.p.m. protocol, peak [Vdot]O₂ was strongly related to AP (r=0·80; R = 0·51) and moderately related to ES (r=?0·41; R =?0·41) and GS (r=0·40; R = 0·30). For the 70 r.p.m. protocol, peak [Vdot]O₂ was found to be strongly related to AP (r=0·94; R=0·88). AV values were not found to have a marked influence on upper body peak [Vdot]O₂ at either crank rate. These data indicate that aerobic power for cycle exercise is the most important determinant of upper body aerobic exercise performance.