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[Gr. energeia, activity]
In physics, the capacity to do work, effect change. Energy is manifested in motion (kinetic energy) or position or chemical bonding (potential energy).
Changes in energy may be physical, chemical, or both. Movement of a part of the body shortens and thickens the muscles involved and temporarily changes the position and size of cells, but intake of oxygen in the blood combined with glucose and fat creates a chemical change and produces heat (energy) and waste products within the cells; fatigue is produced in turn.
SEE: calorie; SEE: energy expenditure, basal

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