Energy metabolism during physical exercise: Towards a current conceptualization in physical activity and sport sciences
Abstract
Energy metabolism is a central topic in physical activity and sports sciences. However, some concepts still require biological contextualization and more precise terminology in scientific literature. In this regard, the purpose of this review was to highlight certain concepts that deserve to be reconsidered and possibly excluded from the vocabulary of exercise and sports sciences. It is argued that the terms “anaerobic” and “aerobic”, used to classify exercises or sports activities, are incorrect and imprecise. Similarly, the persistent use of the term “lactic acid” (i.e., the interchangeable use of lactate and lactic acid, often incorrectly considered the same) consequently leads to the misrepresentation of the phenomenon of “lactic acidosis”, which lacks rigorous biochemical support. Therefore, a conceptual reframing is needed to align with recent findings in exercise biochemistry and molecular biology. The following issues are addressed: i) The estimation of energy system contributions during physical exercise, with emphasis on the most commonly used methods in humans; ii) the classification of energy metabolism—and by extension, exercises—into “anaerobic” and “aerobic”, challenging this dichotomy and proposing a more precise classification into oxygen-independent energy systems (phosphagen and glycolytic) and oxygen-dependent energy systems (mitochondrial oxidative system); iii) the concepts of lactic acid production and lactic acidosis, refuting the idea that lactate accumulation results from oxygen deprivation and highlighting its role as an important metabolic intermediate; and iv) the interaction and contribution of energy systems during physical exertion, stating that energy systems are not activated sequentially but simultaneously, with their predominance depending on metabolic demands. By aligning terminology with contemporary findings in biochemistry and molecular biology, this perspective enhances the understanding and critical analysis of metabolic concepts in sports science education and professional practice, encouraging their adoption based on scientific evidence.
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