Thermodynamics, biochemistry, and metabolism

Abstract

It is critical for the sports nutritionist to understand the chemical underpinnings of exercise and nutrition. For instance, with the knowledge of the phosphagen energy system, it becomes clear how a dietary supplement such as creatine monohydrate might exert its ergogenic effects. Without such knowledge, you are left to guesswork and speculation. Bioenergetics describes how the continuous exchange of matter and energy through an organism affects energy availability; energy exchange is costly in that not all energy is available to perform useful work (e.g., some energy is lost as heat). Energy exchange takes place throughout the anaerobic and aerobic multienzyme metabolic pathways with the breakdown (oxidation) of carbohydrates and fats; the energy held within their molecular bonds is ultimately used to resynthesize adenosine triphosphate (ATP). The chemo-mechanical conversion of ATP (hydrolysis) to allow muscular contraction represents another site of energy exchange. The cycle of ATP hydrolysis and ATP resynthesis is defined as ATP turnover and is described by energy expenditure. Energy expenditure can be interpreted using heat and/or O2 uptake measurements, yet these measures are not always similar; for example, with rapid anaerobic ATP turnover, heat production can exceed O2 uptake. The quantification of total energy expenditure requires estimates or measures of both anaerobic and aerobic ATP turnover during exercise and the recovery from exercise. © 2008 Humana Press.