For example, adequate knowledge of the energy require-ments of physical activities (e.g., running) is important to a coach in planning a training and dietary program for athletes. This same information can be used by an exercise specialist to prescribe exercise for adults entering a fitness program. Therefore, an understanding of human energy expenditure, how it is measured, and its practical significance is critical for the physical therapist, coach, physical educator, exercise specialist, or exercise physiologist. It is the purpose of this part to discuss those concepts necessary for understanding the measurement of human work output and the associated energy expenditure.
UNITS OF MEASURE
In the United States, the English system of measurement remains in common use. In contrast, the metric system, which is used in many other countries, is the standard system of measurement for scientists and is used by almost all scientific journals. In the metric system, the basic units of length, volume, and mass are the meter, the liter, and the gram, respectively. The main advantage of the metric system is that subdivisions or multiples of its basic units are expressed in factors of 10 using prefixes attached to the basic unit. Students not familiar with the metric system should refer to table for a list of the basic prefixes used in metric measurements.
An ongoing problem in exercise science is the failure of scientists to standardize units of measurement employed in presenting research data. In an effort to eliminate this problem, a uniform system of reporting scientific measurement has been developed through international cooperation. This system, known as System international units, or SI units, has been endorsed by almost all exercise and sports medicine journals.
for the publication of research data (21, 22). The SI system ensures standardization in the reporting of scientific data and makes comparison of published values easy. Table contains SI units of importance in the measurement of exercise performance.
■ The metric system is the system of measure-ment used by scientists to express mass, length, and volume.
■ In an effort to standardize terms for the measurement of energy, force, work, and power, scientists have developed a common system of terminology called System International (SI) units.