Energy expenditure physical activity

Although details of the biochemistry of energy transformation have been established for over 50 years, it is only recently that this knowledge has been applied to key life processes in health and disease. This has been driven by several factors appreciation of the importance of provision of chemical energy (i.e. food) for patients, in hospital, provision of chemical energy for physical activity of all kinds and the need to balance energy intake and expenditure for prevention and treatment of obesity. In discussions of the last point, even the mass media refer to the first law of thermodynamics. 

Coward, W. A., Prentice, A. M., Murgatroyd, P. R., Davies, H. L., Cole, T. J., Sawyer, M., Goldberg, G. R., Halliday, D., and Macnamara, J. P. (1984). Measurement of COj and water production rates in man using H, -labelled H2O comparison between calorimeter and isotope values. In Human Energy Metabolism Physical Activity and Energy Expenditure Measurements in Epidemiological Researdi Based Upon Direct and Indirect Calorimetry (A. J. H. van Es, ed.), pp. 126-128. EURO-NUT, The Netherlands. 

The first law states that energy is neither created nor destroyed, which applies to the human body as to any other system. Thus the body mass represents a balance between energy intake (i.e. food) and that expended in various processes in the body, especially physical activity. Thus the law is particularly relevant in weight-reducing diets to overcome obesity or to maintain normal body weight. The subject of obesity is discussed in Appendix 1.5. The general principles of energy intake and expenditure are now discussed. 

Average values for the REE are 7.02 MJ (1680 kcal) per day for normal weight standard adult males (i.e. 70 kg) and 5.60 MJ (1340 kcal) per day for normal weight standard females (i.e. 58 kg). These values conceal as much as 30% variation between individuals, which is greater than changes in energy expenditure caused by normal levels of physical activity or by changes in ambient temperature. (Note difference for a female when calculated from schoheld equations presented above.)... 

Quantitative studies of energy metabolism and fuel utilisation in very prolonged physical activity were performed by Mike Stroud during his Antarctic expedition with Ranulph Fiennes in 1992. One part of the study was measurement of energy expenditure by the dual isotope techniques (Chapter 2). Calculated over the whole expedition, the average daily energy expenditure of Stroud and Fiennes was 29 MJ but on particularly arduous days it increased to... 

It might be considered that running an ultramarathon (various distances from 50 to >100 miles), completing a 24-hour race, racing in the Tour de France or climbing Mount Everest are the ultimate in endurance activities. However, these activities may seem physically insignificant when compared with transantarctic expeditions, such as that carried out by R. Fiennes and M. Stroud in 1992-93. Not only was it a remarkable endurance feat but they carried out smdies on energy expenditure, body composition and nutrition. To illustrate this feat, we can do no better than quote from Mike Stroud s paper. 

The other major component of daily energy expenditure is due to physical activity. For most individuals in the United States, physical activity accounts for 15%-30% of the total daily energy. Most people can sustain metabolic rates 8-10 times their resting value (8-10 METS or multiples of the resting metabolic rate) with reasonably strenuous activi-... 

The daily energy expenditure of an individual includes the energy required for the basal metabolic rate (BMR) and the energy required for physical activity. 

B. This woman s daily energy expenditure is 1560 kcal. Daily energy expenditure equals BMR plus activity. Her weight is 110 lb/2.2 =50 kg. Her BMR (about 24 kcal/kg) is 50 kg X 24 = 1200 kcal/day. She is sedentary and needs only 360 additional kcal (30% of her BMR) to support her physical activity. Therefore, she needs 1200 + 360 = 1560 kcal each day. 

Interestingly, there is an inverse relationship between the degree of physical activity and the prevalence of type 2 diabetes. For every 500-kcal increase in daily energy expenditure, there is a 6% decrease in the age-adjusted risk of type 2 diabetes. This effect is independent of both body weight and a parental history of diabetes. The mechanism of the protective effect of exercise is thought to be an increased sensitivity to insufin in skeletal muscle and adipose tissue. 

To calculate energy requirements in an individual, it is necessary to take into account BMR, physical activity (muscular work), age, sex, height, and weight (Appendix I). The energy requirements of muscular work can be measured. Table 5-4 lists the energy expenditure for various physical activities. 

Examples of Rate of Energy Expenditure during Various Types of Physical Activities of Adults ... 

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