GLOSSARY

Total Daily Energy Expenditure (TDEE) is the total energy used across a day, including rest, processing food and physical activity. Adding exercise again to a value that already includes it would double count that component.

Total expenditure includes energy needed at rest, the thermic effect of food and physical activity. Planned exercise is only part of activity expenditure. Work, walking and spontaneous movement can also matter. When an estimate already includes a component, adding it again double counts energy. Establish whether an exercise value is gross or net of resting expenditure, and use the same convention when comparing days or combining wearable estimates with a daily energy model.

Basal measurements require stricter conditions than many resting measurements, including a postabsorptive state, physical rest and a thermoneutral environment. Resting energy expenditure and basal metabolic rate are closely related but not automatically interchangeable. Recent training, food, stimulants, illness and measurement procedures can affect results. A prediction equation supplies an estimate for a population and its inputs, whereas properly performed indirect calorimetry measures respiratory exchange under the conditions of that particular test.

Physical activity varies in intensity, duration and frequency. A hard training session may coexist with little movement during the rest of the day, and people can change nonexercise activity when training or food intake changes. A device's calorie estimate is not a direct measurement of total daily expenditure. Record the activity context and assess intake, recovery and longer-term body-mass trends together before changing a nutrition plan in response to one reported exercise value.

MET values describe an activity's energy demand relative to a reference resting rate. Standard MET tables are useful for comparing or classifying activities, but the reference may differ from an individual's actual resting metabolism. Multiplying a MET value by duration produces a volume indicator, not a direct measurement of energy expenditure in every athlete. Mechanical efficiency, body size, fitness and conditions can alter actual cost, particularly when values are transferred between different sports or individuals.

Energy requirements depend on body size and composition, activity, life stage and physiological circumstances. A maintenance estimate is a starting point for a defined situation rather than a permanent personal calorie ceiling. Training load, recovery, appetite and changes in body mass help evaluate its usefulness. Growth, illness or a change in training schedule may require reassessment. Adequate energy also needs appropriate carbohydrate, protein, fat and micronutrient provision; matching a calorie total alone does not guarantee a balanced sports diet.

Validity concerns whether a method estimates the intended quantity accurately, while reliability concerns consistency on repetition. A method can repeat well while remaining biased. Technical error and prediction error also describe different sources of uncertainty. Small changes should be interpreted relative to relevant measurement error, with the same protocol used over time. Agreement at group level does not guarantee close agreement for every individual athlete, and switching instruments can create an apparent change that is methodological rather than biological.