Energy Expenditure

Physical activity leads to increased energy expenditure, facilitates the body’s metabolism, and results in health benefits.

Physiology at Firstbeat

Energy expenditure depends on the activity level

The balance between the energy consumed during everyday activities and energy obtained from food determine for example weight changes in the long term. Sufficient energy from balanced diet ensures the overall wellbeing and good recovery, but on the other hand the excess energy easily results in gaining weight. By being physically active energy is consumed more, which helps in weight management. Indeed, one of the most important benefits of physical activity is related to the acceleration of metabolism in the body, both acutely and in the long run. The acceleration of body’s metabolism is related to the intensity and duration of physical activity.

In the field of exercise physiology, oxygen consumption (VO2) is the golden standard for measuring exercise intensity. Both oxygen consumption and energy expenditure (EE) of working muscles increase during exercise. Oxygen consumption is thus intimately linked energy expenditure. Oxygen consumption and energy expenditure can be directly measured using expensive laboratory methods (e.g. direct and indirect calorimetry) but both variables can be also accurately estimated using heartbeat data, and analysis of for example heart rate level and respiration rate from this data.

To construct a more accurate estimate of VO2 when compared with previous estimates that have been based only on heart rate, additional information describing bodily functions have been added to the model by Firstbeat. Neural networks are used to construct a model that derives VO2 from HRV data, using respiration rate and on/off-response information. By this way, the model resulted in the improved accuracy of VO2 estimation. Oxygen consumption values can be further turned into accurate energy expenditure values during daily life and during physical activity.