Field assessment of physical activity and energy expenditure among athletes

A large number of physical activity measures are currently utilized in the field setting to profile activity in terms of amount and type of movement performed, and many of these tools are also employed to predict energy expenditure. Physical activity is a multi-faceted construct, and although there are numerous techniques for assessment there is no "gold standard" measurement method.1 In contrast, energy expenditure, which is a biological variable reflecting the sum of internal heat produced by external work, can be measured using well-accepted gold-standard methods. It is important to remember that physical activity is a behavior that results in an elevation of energy expenditure above resting levels, and although these terms are often used interchangeably, they are inherently different and can be measured differently.2 The techniques available to researchers, coaches, and athletes to measure physical activity and energy expenditure are vast, but the applicability of the different measurement tools will depend on the aspect of physical activity or energy expenditure that needs to be measured.