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ABSTRACTHumans have successfully inhabited every continent on this planet. Our ability to survive and thrive in such a wide range of environments is fascinating, particularly from an energetic perspective. As knowledge of human total energy expenditure (TEE, kcal day−1) has deepened, so too has the ability to interpret observable patterns in human metabolic physiology and apply these interpretations to our evolutionary history. This review examines the basic components of human TEE as well as the interactions among these components. This is followed by a discussion of two recent theories regarding limits on the amount of calories used and how those limits may mediate life‐history variables. Finally, this review provides a look ahead into the lesser explored areas of human TEE, suggesting future areas of research. The ability to measure how much energy humans expend and how they allocate that energy is a powerful tool that enables anthropologists to understand not only our past but also our present. [energy expenditure, thermoregulation, life history]

The federal government has made deficit reduction one of its prime policy goals for several years now. This deficit is conventionally defined as that portion of the government's spending not covered by revenues, that is, in financial terms. Yet, it has become increasingly understood that Canada is accumulating an environmental deficit just as it is running up a financial deficit. This environmental deficit is evident in a continuing deterioration in environmental quality and in unsustainable forestry, fishery, and agriculture practices which deplete productive resources faster than they can be replenished. Just as Canadians are passing on a high level of financial indebtedness to future generations by living beyond their means, so are they leaving a degraded natural environment to their children by polluting it and over-exploiting its renewable resources. In both instances, future generations will face more restricted choices.

Twenty-five male college students were measured for oxygen consumption during a simple stimulus-response task. Performance, as measured by reaction time and speed of arm movement, maintained a steady state except for a period of work decrement which had no relationship to initial speed or isotonic endurance. Oxygen consumption was maintained at a steady rate throughout the task. Fatigue, work decrement, and endurance were not reflected in oxygen consumption rates.

This review examines the proximate, ecological, and evolutionary determinants of energy expenditure in humans and primates, with an emphasis on empirical measurements of total energy expenditure (TEE). Body size is the main proximate determinant of TEE, both within and between species; physical activity, genetic variation, and endocrine regulation explain substantially less of the variation in TEE. Basal metabolism is the single largest component of TEE, far exceeding the cost of physical activity, digestion, growth and reproduction, and thermoregulation in most instances. Notably, differences in physical activity do not generally result in corresponding differences in TEE, undermining the utility of activity-based factorial estimates of TEE. Instead, empirical measurements of energy expenditure in humans and other primates suggest that the body adapts dynamically to long-term changes in physical activity, maintaining TEE within an evolved, and relatively narrow, physiological range.

We assessed the ability of the Polar activity recorder (AR) to measure energy expenditure (EE) during military training. Twenty-four voluntary male conscripts participated in the study and wore an AR on the non-dominant wrist 24 h a day for 7 d. The AR analyzed and stored the frequency of hand movements (f_hand) into memory at 1 min intervals. The relationship between f_hand and EE was studied over a 7 d period of military training using the doubly labeled water (DLW) technique. In addition, the relationship between f_hand and EE was analyzed during walking and running on a treadmill with an indirect calorimeter (IC), and f_hand was measured during a supervised 45 min field march test where the conscripts carried combat gear. EE was expressed as physical activity level (PAL), total energy expenditure (TEE), and activity-induced energy expenditure adjusted for body mass (AEE/BM). Over the 7 d period, f_hand alone explained 46% of inter-individual variation in PAL(DLW). After inclusion of body height and mass in the model used to predict PAL(DLW) from f_hand, a very high positive correlation and a low standard error of estimate (SEE) were observed between the AR and DLW techniques: for TEE r = 0.86 (p < 0.001), the SEE was 6.3%, and for AEE/BM r = 0.84 (p < 0.001), the SEE was 12.8%. In the treadmill exercise, f_hand correlated highly with PAL(IC) (r = 0.97 +/- 0.02). In the 45 min field march test, the AR measured similar f_hand as on the treadmill at the same speed. In conclusion, the wrist-worn AR can be regarded as a reliable and valid method for assessing EE during intensive training.

Abstract

Introduction
The assessment of energy expenditure (EE) at workplaces maintains a central topic in occupational health due to increasing work-related issues. Today 80% of employees in the healthcare system are women. Limited research concerning their physical activity at work is available. The purpose of the study was the investigation of body composition, maximum physical capacity and quantification of physical work activity for female healthcare workers under real-time conditions.


Methods
Occupational physical activity (PA) of 33 female healthcare workers in a university hospital was quantified. Health associate professionals (HAP), health professionals (HP), and females working from cleaners and helpers (CH) department participated. All underwent cardio pulmonary exercise test. For every working task VO2, VCO2 and RER were measured and EE was calculated individually for each task.


Results
Forty-two different working tasks were identified and grouped in seven categories to compare physical activity (PA): 'office and laboratory work', 'bedside patient care', 'instrument reprocessing, packing boxes', 'walking with patient, or alone', 'pushing carts or wheelchairs', 'strenuous cleaning in bent posture' and 'lifting heavy boxes, weights or items'. By comparing groups of healthcare workers, CH and HAP spent significant (p &lt; 0.01) more EE (in kcal/min) 3.9 resp. 3.2 than HP 2.5. Light PA e.g. office and laboratory work (2.7 ± 0.6) and bedside patient care (2.9 ± 0.7) were accomplished by HP and HAP while HAP and CH performed moderate PA such as 'packing boxes' (3.6 ± 0.8), 'pushing carts' and 'strenuous cleaning' (4.7 ± 0.9). Work performed by CH and HAP, i.e. 'strenuous cleaning' and 'lifting heavy items' showed highest kcal per kg Fat Free Mass (FFM) per hour with 5.80 [4.05–7.81] and 6.94 [5.18–9.03] kcal/kgFFM/h.


Conclusion
Our findings lend preliminary support to the hypothesis that the majority of activities in female healthcare workers were of low and moderate PA and can be accomplished by middle aged and even older female workers. CH performed tasks with heavy physical activities (PA) like cleaning and lifting heavy weights. HAP performed light/moderate PA below their maximum physical capacity.

BackgroundWhen developing walking programmes for improving health in adults with Down syndrome (DS), physical activity professionals are in need of an equation for predicting energy expenditure. We therefore developed and cross‐validated an equation for predicting the rate of oxygen uptake (VO2; an index of energy expenditure) for adults with and without DS.MethodA total of 469 VO2 observations during walking across different speeds were available from 54 adults with DS and 61 adults without DS.ResultsSignificant predictors of VO2 were speed, speed square, group and group‐by‐speed interaction. Separate models for each group showed that speed and its square significantly predicted VO2. Absolute per cent error was small and did not differ between groups.ConclusionAdults with DS have different VO2 response to walking speed from persons without DS. VO2 is predicted from speed with acceptable accuracy for persons with DS.