Metabolic Differences
Metabolism refers to all of the energy-requiring chemical reactions occurring inside your body. At any one time, trillions of reactions are going on inside of you, including the growth of new tissue, muscle contraction, and the breakdown of food for energy. The resting metabolic rate—the amount of energy needed during resting conditions—is lower in females because of their smaller body mass and muscle mass. When you run, your metabolic rate increases dramatically because of the increased demand for energy. The faster your metabolic pathways can use the available fuel to regenerate energy for muscle contraction, the faster you will be able to run any race.
While your nervous system controls your body’s faster functions, like the initiation of reflexes and movement, hormones control the slower functions, like the regulation of growth and metabolism and the development of reproductive organs. Much of metabolism is under the direction of hormones, which act as conductors, initiating signals that lead to the transportation and use of fuel. And the two predominant fuels for running are carbohydrate and fat, which provide energy on a sliding scale. At slower speeds, your muscles rely more on fat and less on carbohydrate, and as you increase your running pace, the energy contribution from fat decreases while the energy contribution from carbohydrate increases.
