Energy consumption and its measurement in physical activity.

The low daily energy consumption of the average adult in the developed countries may be increased in certain individuals either because of the occupation or by voluntary activity in leisure. Jogging is one example of this. However, we have little objective information on activity within the population and epidemiologically this is a serious deficiency. There is a need for not only quantitative data on duration of activity but also its level of strenuousness. On the other hand, depending on the purpose of the measurement, it may not often be necessary actually to measure energy expenditure--heart rate measurement or energy values taken from published tables may be adequate. Indeed, energy expenditure or VO2 may not only be unnecessary but even misleading in some cases. When knowledge of energy consumption is required, (for example, in specialized biochemical or in nutritional studies) heart rates will not usually give an accurate enough prediction and oxygen uptake has to be measured. This has to be converted to energy units either by using the RQ or Weir's (1949) formula. Errors of up to +/- 10% may be common here, especially in short-term measurements in exercise. Weir's formula is more likely to lead to larger error and perhaps should be superceded.