ponent of physical fitness, including aerobic fitness and aerobic capacity. These terms are essentially synonymous with cardiorespiratory endurance, which is the term used in this report. Forms of exercise that depend on cardiorespiratory endurance include vigorous distance running, swimming, and cycling. This fitness component also affects a person’s ability to perform, without undue fatigue, less intense, sustained whole-body activities, such as brisk walking, stair climbing, and home chores. People with good levels of cardiorespiratory endurance can perform large-muscle, whole-body exercise at high intensity for at least moderate durations before experiencing fatigue, and they can comfortably perform light- to moderate-intensity exercise for extended periods.

Cardiorespiratory endurance depends on the body’s ability to support skeletal muscle activity through high rates of aerobic metabolism. The ability to produce energy at high rates through aerobic metabolism during exercise depends on three physiologic functions: (1) transport of oxygen from the atmosphere to the active muscles through the actions of the cardiorespiratory system, (2) consumption of oxygen in the aerobic metabolic process in the cells of the active muscles, and (3) removal of waste products. People with high levels of cardiorespiratory endurance typically have highly functional cardiorespiratory systems (i.e., heart, lungs, blood, blood vessels), and their skeletal muscles are well adapted to the use of oxygen in aerobic metabolism.

Higher levels of cardiorespiratory endurance have been associated with a wide range of health benefits in adults, including a lower risk of cardiovascular disease (Arraiz et al., 1992; Blair et al., 1989; Sandvik et al., 1993), type 2 diabetes (Colberg et al., 2010), hypertension (Blair et al., 1984), certain cancers (Oliveria et al., 1996), and premature mortality from all causes (Blair et al., 1989, 1993, 1995). The linkage between cardiorespiratory endurance and health in youth is discussed later in the chapter.

CARDIORESPIRATORY ENDURANCE TESTS

The gold standard measure of cardiorespiratory endurance is maximal aerobic power (VO2max)—the greatest rate at which a person is able to consume oxygen during sustained, exhaustive exercise. In the laboratory, VO2max is typically measured while a person performs maximal, graded exercise on a treadmill or cycle ergometer. VO2max can be expressed in terms of liters of oxygen consumed per minute (l/min), or the values can be normalized for differences in body size and expressed as milliliters of oxygen consumed per kilogram of body weight per minute (ml/kg/min). VO2max is known to be a key physiologic determinant of cardiorespiratory endurance and has typically been used as the criterion measure in the validation of field measures of cardiorespiratory endurance. Many field measures of this fitness component have been studied and used in various fitness test batteries around the world (see Table 2-6 in Chapter 2).



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