OBJECTIVES On the completion of this chapter you will be able to: 1. Defi ne the basic defi nitions associated with bioenergetics. 2. Understand the basic principles behind thermodynamics. 3. Develop an understanding of the concept of energy transfer. 4. Describe the biochemical reactions associated with various energy-transfer pathways in the body. 5. Explain the basics of energy expenditure, the methods for measuring energy expenditure, and the relationship of energy expenditure to exercise.

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... BSTRACT Skeletal muscle is a highly organized tissue designed to produce force for postural control, movement, and even breathing. Various architectural designs, varying amounts of muscle proteins (e.g., enzymes or myosin), and different isoforms of many muscle proteins provide for a wide range of force-producing, biochemical, and metabolic characteristics. Additionally, the ability of skeletal muscle to adapt to the demands placed upon it, such as increased mitochondrial volume associated with endurance training or increased muscle fi ber crosssectional area as a result of strength training, demonstrates a tremendous plasticity. For the sports nutritionist, a fundamental understanding of the structure and function of skeletal muscle is important inasmuch as the adaptive response to various contractile and nutritional perturbations are manifest in this tissue. It should be noted that there is a large variation among individuals with regard to the magnitude of muscle adaptability to various types of training. Differing muscle characteristics, such as muscle pennation and fi ber type, and variation in degree of adaptability among individuals partially explain the wide range of differences in aspects of exercise performance, such as muscular endurance or strength.