Health-Related Measures of Children's Physical Fitness

Article excerpt

Measurement of physical fitness among children has been commonplace in physical education programs and in public health surveys throughout the 20th century. [1,2] Accepted approaches to fitness testing have evolved steadily over the past century. In this article, a concise summary of physical fitness measurement procedures most widely applied with children is provided. Emphasis is given to field measures, since these are the measures of choice in educational settings and in public health surveys. Laboratory measures are of interest primarily because they are used to validate field measures. This review focuses exclusively on measures of fitness thought to be "health-related."

HEALTH-RELATED PHYSICAL FITNESS

Physical fitness has been literally and operationally defined in many ways. [3] Almost always, it has been viewed as a multifactorial trait related to the capacity for movement. Casperson et al [4] proposed that physical fitness be defined as a set of attributes that people have or achieve that relates to the ability to perform physical activity. Such definitions have been operationalized in broad terms by identifying a list of fitness components, which are related to one or more type of human movement (Table 1). Though physical fitness and physical activity are related, they are not synonymous. In free-living populations these two variables are moderately associated. In children ages eight-nine, the multiple correlation between mile run time and a set of physical activity parameters was 0.2. [5]

Health-related physical fitness gained common use in the late 1970s and has been used widely to denote a narrower concept than physical fitness. Health-related physical fitness has been defined as a state characterized by a) an ability to perform daily activities with vigor, and b) demonstration of traits and capacities that are associated with low risk of premature development of the hypokinetic diseases. [3,6] This term encompasses only the four components for which research findings and clinical experience indicate a relationship to disease prevention or maintenance of a good functional capacity for day-to-day living. [7-10]

CARDIORESPIRATORY ENDURANCE

The most widely used laboratory measure of cardiorespiratory endurance is directly measured maximal aerobic power ([VOl.sub.2] max). [VO.sub.2] max is measured by collecting and analyzing expired air samples while subjects perform graded, maximal exercise on an ergometric device such as a treadmill, leg cycle ergometer, or arm crank ergometer. In most cases, this test was used as the criterion against which field measures were validated. [VO.sub.2] max is an attractive measure because its physiological basis is well understood, widely accepted procedures exist for its measurement, and it is highly reliable. [11] It also carries a high level of construct validity because it correlates well with "the ability to perform moderate intensity, whole body activity for extended periods of time." However, direct measurement of [VO.sub.2] max is a relatively expensive, time-consuming process that usually precludes its use with large groups. In addition, [VO.sub.2] max testing requires a near-exhaustive effort that can be problematic with younger children or those with physical or mental limitations. Alternative laboratory measures such as the rate of power output at the ventilatory anaerobic threshold or lactate threshold [12] have been developed, but have not gained wide use with pediatric populations.

In field settings, distance runs are the most commonly used measures among children. The most common test is the mile run/walk for time in which children complete the mile distance as quickly as possible, running the full distance if possible, but walking as necessary. This test is included in several current youth fitness test batteries promoted nationally [13-15] and was included in the National Children and Youth Fitness Studies (NCYFS). …