What is the primary unit of measurement for energy expenditure in physical activity?

The primary unit of measurement for energy expenditure in physical activity is the kilojoule. This unit is widely used in nutrition and exercise science because it provides a convenient way of expressing the amount of energy derived from food and expended during physical activities. One kilojoule is equal to 1,000 joules, making it a larger and more practical unit for most dietary and exercise contexts, where energy measurements typically involve significant values.

While calories are also a commonly recognized measure of energy, especially in dietary terms, in many countries, particularly those using the metric system, kilojoules have become the standard for scientific and medical discussions about energy expenditure and nutrition. Joules, though technically correct as a unit of energy, are less frequently used in practice due to their smaller scale compared to kilojoules and calories. Newtons, on the other hand, are a unit of force and do not pertain directly to energy expenditure, making them irrelevant in this context.