Regular physical activity increases basal metabolic rate (BMR) and total daily energy expenditure (TDEE) due to increased muscle mass and metabolic activity.

The phosphagen system is the primary energy system used during high-intensity, short-duration activities, providing immediate energy through stored ATP and creatine phosphate.

Cellular respiration is the primary mechanism by which the body converts food energy into ATP, the usable form of energy for cells.

Muscle contraction primarily relies on ATP, which provides the energy needed for muscle fibers to contract.

Basal metabolic rate (BMR) refers to the energy expended by the body at rest to maintain essential physiological functions.

Fats provide the most energy per gram, yielding approximately 9 calories per gram, compared to carbohydrates and proteins, which provide about 4 calories per gram.

Running a marathon requires significantly more energy expenditure compared to sitting, walking, or sleeping due to the high intensity and duration of the activity.

An energy imbalance, where energy intake exceeds energy expenditure, leads to weight gain.

The energy stored in the chemical bonds of food molecules is known as potential energy, which can be converted into kinetic energy during metabolism.