Before you can study about physiological responses to exercise, you have to learn about how to quantify exercise intensity, and how we can quantify the mechanical power from certain exercise modes. This is important, as knowing mechanical power during exercise means we can eventually quantify energy expenditure, and appreciate individual differences in endurance, strength, and power components of physical fitness. This, in turn, means we can then establish solid principles from which to exercise train to improve physical fitness. I am always frustrated at how little attention this content receives in most exercise physiology textbooks. You cannot do well in your study of exercise physiology if you do not have a good grounding in ergometry, and then calorimetry, which is the Section that follows. You need to dust the cob webs of your algebra, as you need it for this Topic. You also need to familiarize yourself with different units of energy, work and power. If you know the energy that is used during exercise, and you know the mechanical energy produced, and you can calculate the efficiency that the body can convert chemical to mechanical energy, which approximates 25 to 30%. That means the human body converts about 30% of its energy expenditure to power development during exercise. In other words, about 70% of the chemical energy we break down to support exercise is not diverted to mechanical work and power, but lost through waste products (metabolites such as lactate [only the lactate not catabolized during or after exercise], alanine, urea and CO2) and heat. Commit effort to your understanding of energy, work and power during exercise, and you will impress others with your knowledge and command of exercise physiology.
Recommended sequence of topics: