The purpose of this article is to provide the reader with the latest research findings on the relationship between physical activity and physical fitness in children. This article will be divided in three distinct sections including
- A review of literature on the following sub-topics
- The relationship between physical activity, physical fitness and health in children
- The relationship between physical activity and physical fitness in children
- Tracking of physical activity and physical fitness in children and adolescents
- Summary and recommendations.
The relationship between physical activity and physical fitness in children and youth has gained considerably attention in the past decade (Baranowski, Bouchard et al., 1992; Pate et al., 1990; Riddoch & Boreham, 1995; Sallis et al., 1993). There is evidence that lack of physical activity (Caspersen et al., 1998; Despres et al., 1990; DuRant et al., 1993) and fitness (Despres et al., 1990; Sallis et al., 1988) in children has been associated with many health related problems. According to the Surgeon General Report (U.S. Department of Health and Human Services, 1996) only about one-half of American young people participate regularly in vigorous physical activity. The report also indicates that participation of children in physical activity declines greatly as age or grade in school increases.
In a consensus statement, the relationship among physical activity, physical fitness, and health is that physical fitness is one of the mediators of physical activity effects on health outcomes (Bouchard, Shepard, Stephens, Sutton, & McPherson, 1990). In adults, increased physical activity and fitness have been associated with positive health outcomes. Conversely, there is evidence that low levels of habitual physical activity (Blair, Kohl, Gordon, & Paffenberger, 1992; Paffenberger, Hyde, Wing, & Hsieh, 1986) and low levels of physical fitness have been associated with increased all-cause mortality rates (Blair, Kampert, Kohl et al., 1996; Blair, Kohl, Barlow et al., 1995; Blair, Kohl, Paffenberger et al., 1989). In children, there is also evidence that both increased physical activity and physical fitness are associated with improved risk factors for cardiovascular disease (Caspersen, Nixon, & DuRant, 1998; Despres, Bouchard, & Malina, 1990; DuRant et al., 1993; Sallis, Patterson, Buono, & Nader, 1988). Thus, according to the Council for Physical Education for Children – COPEC- (1998), children should be involved in physical activity on most days of the week for 30 to 60 minutes (i.e., moderately intense activity).
One major reason for promoting activity among children is that physical activity has the potential to track into adulthood (Dennison, Straus, Mellits, & Charney, 1988; Janz et al., 2000; Malina, 1996; Pate, Baranowski, Dowda, & Trost, 1996; Raitakari et al., 1994; Twisk, Kemper, & Mechelen, 2000). In light of this potential, it is important to identify at an early age the children who fall short of these guidelines so successful behavior and intervention strategies can be established accordingly. The best time to implement intervention programs would be during the early school-age years when most students are exposed to health and physical education programs. In addition, lifetime behavior habits usually are established during childhood, making it a crucial period to both educate and encourage children to engage in regular physical activity or to reinforce their existent physical activity habits (Pangrazi, Corbin, & Welk, 1996; Sallis, Simons-Morton et al., 1992).
REVIEW OF THE LITERATURE
The Relationship Between Physical Activity, Physical Fitness and Health in Children
According to Bouchard and colleagues (1990) in their consensus statement, the relationship among physical activity, physical fitness, and health is that physical fitness is one of the mediators of physical activity effects' on health outcomes. In children, there is evidence that both increased physical activity (Caspersen et al., 1998; Despres et al., 1990; DuRant et al., 1993; Sallis, Patterson et al., 1988) and physical fitness (Despres et al., 1990; Sallis, Patterson et al., 1988)are associated with improved risk factors for cardiovascular disease.
Sallis and co-workers (1988) investigated the association between physical activity, cardiovascular fitness, and cardiovascular risk factors in 290 children (148 boys and 142 girls). The average age for both boys and girls was 11.9 and 11.8 years, respectively. Measurements included cardiovascular fitness--VO2max (submaximal graded exercise test), blood lipids (HDL and LDL cholesterol levels), blood pressure, body mass index (BMI) and physical activity (measured by the 7-day physical activity questionnaire). For the activity instrument subjects reported time spent in sleep and in moderate, hard, and very hard intensity activities. An index of (kcal/kg/day) caloric expenditure was derived from the reports. Subjects also were asked to rate themselves on their levels of physical activity on a 5-point scale ranging from "much less active" to "much more active." The results were that cardiovascular fitness was significantly (p < .001) correlated with all risk factors (except HDL/LDL in males) including systolic and diastolic blood pressure (r = -.33, -.31, -.38, -.21, respectively for boys and girls), BMI (r = -.58 and -.65 for boys and girls, respectively) and resting heart rate (r = -.30 and -.21 for boys and girls). Finally, the activity level rating was correlated with BMI (p < .001, r = -.28) and heart rate in boys (p < 0.05, r = -0.15). For girls, the activity level rating was correlated with diastolic blood pressure (r not reported), heart rate (p < 0.05, r = -0.15), and HDL/LDL (p < 0.05, r = 0.17). For both boys and girls, the activity level rating was not correlated with either energy expenditure (r = 0.12) or predicted VO2max (r = 0.13). DuRant et al. (1993) measured body composition, resting heart rate, cardiovascular fitness variables and serum lipid and lipoprotein levels in 123 children (age = 4 to 5 years). The researchers concluded that children who had higher levels of physical activity had lower levels of body fat, triglycerides, and more favorable serum lipid and lipoprotein than less physically active children.
- "r" stands for how strong a relationship (correlation) is between two measurable parameters. Most studies in Exercise Physiology agree that a strong relationship should have an r of .80 or higher. In the area of children's fitness and activity level, most experts agree to a r = .30 or higher.
- "p" stands for Power or the percentage level of statistical significance. Typical values are either equal or less to .05 (which means that 5 times out of a 100 there will be an error in what is being tested) or .01 (which means that 1 time out of a 100 there will be an error in what is being tested;). Thus, in order to achieve statistical significance, tests results must fall within this power of error (less or equal to p = .05 or .01).
In addition, lack of physical activity also can influence the development of obesity among children (Troiano, Flegal, Kuczmarski, Campbell, & Johnson, 1995). There is also evidence that body fatness tracks into adulthood (Clarke & Lauer, 1993; Dipietro, Mossberg, & Stunkard, 1994; Rimm & Rimm, 1976); hence, the importance of promoting physical activity and fitness during childhood. According to Clarke and Lauer (1993) who studied 2,631 school children 9 to 18 years of age for 10 years, obesity often developed in childhood and tracked from adolescence into adulthood. The data indicated that 63.5% of females and 56.8% of males (21-25 years of age) who had been in the upper quintile for body weight at ages 9 to 10 years, were in the upper quintile for body weight as adults. Similar results were found for BMI (Body Mass Index) measurements where adults who were in the upper quintiles for BMI as children were in the upper quintile for BMI as adults.
According to Rimm and Rimm (1976), childhood obesity may track into adulthood. The authors investigated the association between juvenile obesity and severe adult obesity in 73,532 women. The subjects completed a questionnaire regarding their body weight history as children. Analysis of data showed that severely obese women (>100% of ideal body weight which was based on desirable weights from Metropolitan Life Insurance Company, 1959) regardless of age, were 2.4 times more likely to have been fat. (i.e., relative obesity was determined by use of the obesity index ratio: weight/height) children than normal weight women. The authors concluded that the risk for a fat child developing severe obesity was much greater than that of a non-fat child. In addition, Dipietro et al. (1994) reported a 40-year follow-up on a sample of 504 overweight children (233 males and 271 females). At the beginning of the study the participants ranged from 2 months to 16 years of age. Follow-up information was acquired via questionnaire at 10-year intervals, which included the following: (a) body mass index (BMI), (b) prevalence of cardiovascular disease and diabetes, (c) cancer, and (d) mortality (from death certificates). Results showed a steady increase in BMI measurements from childhood to adulthood in both genders (BMI = 19.4 kg/m2 at age 0-2 years to 28.7 kg/m2 at age 55 and 20.5 kg/m2 to 29.2 kg/m2 at age 55 for males and females, respectively). Females were heavier than their male counterparts from puberty onward. In addition, subjects who died by the 40-year follow-up and those reporting cardiovascular disease were significantly heavier (p < .05) at puberty and in adulthood when compared to the healthier subjects. The authors concluded that childhood adolescence obesity may track into adulthood. In summary, it appears that increased physical activity and physical fitness have positive effects on health-related risk factors.
Relationship between Physical Activity and Physical Fitness in Children
The relationship between physical activity and physical fitness in children and youth has gained considerably attention in past decade (Baranowski, Bouchard et al., 1992; Pate et al., 1990; Riddoch & Boreham, 1995; Sallis et al., 1993). Most studies have focused on one or more components of physical fitness including cardiovascular endurance, muscular endurance and strength, body composition, and flexibility. Also, physical activity has been measured in terms of total caloric expenditure, activity participation questionnaires, and total time spent in one or more activities (Andersen, Ilmarinen et al., 1984; Atomi et al., 1986; Beunen et al., 1992; Katzmarzyk et al., 1998; Morrow & Freedson, 1994; Pate et al., 1990; Sallis et al., 1993). Thus, given the evidence that lack of physical activity (Blair, Kohl et al., 1992; Caspersen et al., 1998; Despres et al., 1990; DuRant et al., 1993; Paffenberger et al., 1986; Sallis, Patterson et al., 1988) and physical fitness (Blair, Kohl, Barlow et al., 1995; Blair, Kohl, Paffenberger et al., 1989; Despres et al., 1990; Sallis, Patterson et al., 1988) in both adults and children has been associated with many health related problems it is important to understand the strength of these associations.
In their 5-year longitudinal study on 25 girls and 27 boys (ages 14-18 years), Andersen and colleagues (1984) related physical activity to maximal aerobic power. Physical activity scores were based on sport participation. Children were interviewed about their participation in sports and play in the previous year. The type of activity and the amount of time spent were assessed and the intensity of the activity was estimated in terms of METS (multiple of resting metabolic rate). A total score (i.e., sport activity score) was calculated by summarizing the product of hours/year and METS. Maximal oxygen uptake (VO2max) was determined by the direct method using cycle ergometry (i.e., the expired air was collected using the Douglas bag). The results showed a small but significant correlation (p < .001) between physical activity and maximal oxygen uptake in boys (VO2max expressed on the basis of total body mass or lean body mass) of 0.31 and 0.40, respectively. In girls, the correlation was also significant (p < .05, r = 0.19 for VO2max expressed on the basis of total body mass and p < .02, r = 0.23 for VO2max expressed on the basis of lean body mass). The authors concluded that there was a tendency towards better fitness with increased habitual physical activity (based on the "sport activity score"), although there were subjects who scored high in the sport activity score but yet demonstrated a low level of maximal oxygen uptake. The authors suggested that other factors such as nutrition, diseases, hormonal status, among many others, can also influence ones' physical performance capacity.
Atomi et al. (1986) studied the physical activity levels and maximal oxygen uptake (VO2max) of 11 Japanese boys (9-10 years). Measurements included a maximal treadmill test, body fat (sum of triceps and scapular skinfold measurements) and continuous heart rate recording (8 to 12 hours for 3 days) of exercise intensity of daily physical activities. Mean total time of activities with heart rate above the level corresponding to 60% of VO2max (heart rate = 155 +/- 10 bpm) correlated (r = 0.74) with maximal oxygen uptake (p <.01). The authors concluded that the volume (intensity and duration) of daily physical activity above heart rate corresponding to 60% of VO2max may contribute to increase maximal oxygen uptake.
Pate et al. (1990) investigated the association between two measures of physical fitness (i.e., 1.6 km run/walk and sum of three skinfold thickness) and various physical activity measures (i.e., 20 activity variables were measured via a parent and teacher questionnaire) in a sample of third- and fourth-grade students (n = 1,150 boys and 1,202 girls). Several physical activity measures were correlated with one or both of the physical fitness measures. The authors reported that the best individual predictors of fitness were the global activity ratings provided independently by parents and teachers (r = 0.17 to 0.33, p < .05). They concluded that physical activity and physical fitness were significantly, although moderately, associated in young children.
Similarly, Sallis et al. (1993) examined the associations between multiple measures of physical activity and multiple components of health-related physical fitness in a sample of fourth-grade students (n = 274 boys and 254 girls). Physical activity measurements included four child self-reports of activity (i.e., weekday, weekend, summer class, and summer team sports), a parent's report of their child's activity, and one objective measure of weekday activity using an accelerometer. Physical fitness measurements included cardiovascular endurance (i.e. 1 mile-run test), abdominal muscle strength and endurance (i.e., 1 minute sit-up test), muscular endurance and strength of the upper body (i.e., pull-up test), hamstring flexibility (i.e., sit and reach test), and body composition (i.e., calf and triceps skinfolds). All tests were performed according to the FITNESSGRAM testing protocol.
The results of the six measures of physical activity (four child activity self-reports; parent's report of their child's activity, and one activity measured by an accelerometer) were combined into a one factor--physical activity index--which in conjunction with each of the physical fitness components, were entered into a regression equation. Canonical correlations also were performed between all physical activity and physical fitness measures. In general, more active children showed enhanced physical fitness components when compared to less active children. For instance, post- hoc analyses revealed that more active boys had smaller skinfold measurements (p < .04) as well as performed more pull-ups (p < .02) than less active boys (p < .02). Regardless of gender, more active children did more sit-ups (p < .01), and scored higher on flexibility (p < .02) than less active children. Canonical correlations were 0.29 for the total sample (p < .001), 0.37 for the boys (p < .001), and 0.29 for the girls (p < .001), indicating significant associations between increased physical activity and physical fitness.
The authors concluded that active children appear to engage in a sufficient variety of activities to enhance different components of physical fitness.
Moreover, the data from the National Children and Youth Fitness Survey (Dotson & Ross, 1985) on children aged 10 through 17 reported a significant relationship (p < .001, r not reported) between participation in physical activity and the mile walk/run performance test for cardiovascular fitness. More specifically, the authors reported that students who scored in the optimal range (above 75th percentile) on the mile walk participated in a significantly greater number of high-intensity cardiorespiratory activities at an appropriate level (3 days per week for 20 minutes or more) than students in the acceptable and below average range (40th to 75th and < 40th percentile, respectively).
Further, Katzmarzyk et al. (1998) investigated the relationship between indicators of physical activity and health-related fitness in youth 9 to 18 years of age (n = 356 boys and 284 girls). The sample was divided into three age groups by gender, 9-12, 13-15, and 16-18 years of age. Measures of physical activity included daily energy expenditure and estimates of activity and inactivity, while fitness variables included body composition, cardiovascular endurance and muscular strength. Physical activity was assessed via a 3-day activity record, which included one weekend day. Energy expenditure was estimated using this method. Thus, the entire day was divided in 95 periods of 15 minutes. Individuals were instructed to record the energy expenditure on a scale of 1 to 9 of the dominant activity period based on a list of activities corresponding to each category (1 to 9). Estimates of energy expenditure were calculated by summing the activity scores throughout the day. The amount of time spent watching television was used as an indicator of physical inactivity. Moreover, four indicators of health-related fitness were measured including submaximal work capacity, muscular strength, muscular endurance, and subcutaneous fatness. Submaximal work capacity was determined during three 6-minutes exercise bouts on a Monark cycle ergometer, designed to elicit a heart rate of about 170 beats per minute. Endurance of the abdominal musculature was measured as the number of sit-ups performed in 60 seconds, whereas muscular strength of the quadriceps muscle group of the left leg was measured by maximal voluntary isometric contraction at a knee angle of 90 degrees. Subjects performed five maximal knee extensions, each separated by a 30-second rest period, and force in kilograms was recorded with a strain gauge attached at the ankle. The highest tension was used as a measure of leg muscle strength. Subcutaneous fatness was determined by the sum of six skinfold sites including triceps, biceps, subscapular, suprailiac, abdominal, and medial calf.
The correlations between physical activity and muscular endurance/strength and sum of skinfolds in girls (9-12 years) were low and not significant (r = 0.16, 0.14, -.11, respectively). However, the correlation between physical activity and aerobic capacity in girls (9-12 years) was significant (r = 0.25, p < .05). In girls (13-15 years of age) correlations between physical activity, aerobic capacity, muscular endurance and sum of skinfolds were significant (r = 0.19, 0.27, -.18, p < .05, respectively). For older girls (16-18 years of age) physical activity, aerobic capacity, and muscular strength were correlated (r = 0.27, 0.21, p < .05, respectively). In boys (9-12 years of age), physical activity and aerobic capacity were correlated (r = 0.28, p < .05). Muscular endurance and strength were correlated to physical activity in boys 13 to 15 years old (r = 0.24, 0.27, p < .05, respectively). Aerobic capacity and muscular endurance in older boys (16-18 years of age) were correlated to physical activity (r = 0.21, 0.22, p < .05, respectively). Finally, canonical correlations between physical activity and fitness variables ranged from 0.33 in 9- to 12-year-old boys to 0.46 in 9- to 12-year-old girls indicating that the variance shared by the fitness and activity variates ranged from 11 to 21%. All canonical correlations were significant (p < .05) for girls across all age groups and boys (13-15 year old). The authors concluded that there was a weak relationship between physical activity and fitness variables and that the large part of variability (80% to 90%) found in the fitness variables was not accounted for by physical activity as measured in the study.
Finally, in the Leuven Growth study of Belgian boys (Beunen et al., 1992), the effects of increased physical activity upon physical growth, maturation and performance were investigated in a sample of 64 active (n = 32) and non-active (n = 32) boys who were followed from 13 to 18 years of age. All tests were performed on a yearly basis and included the following: (a) anthropometric measurements, (b) battery of physical fitness tests, (c) assessment of skeletal maturation, and (d) sports participation through written questionnaires. Active boys were those who participated in sports activities for more than 5 hours per week during each of the first 3 years of the study in addition to school physical education classes. Non-active boys were those who participated in sport activities less than 1.5 hours per week in addition to school physical education classes. The results showed that active boys performed better than inactive boys only in the pulse rate recovery after the step test and the flexed arm hang. The authors concluded that growth and maturation in boys were not influenced by level of physical activity either positively or negatively, although there was a positive influence on components of fitness as related to aerobic power (i.e., heart rate recovery) and muscular endurance (i.e., flexed arm hang).
In summary, the relationship between physical activity and fitness is weak to moderate. Since the lack of physical activity and fitness in both adults and children has been associated with many health related problems it is important to further study these associations so early intervention strategies can be established.
Tracking Physical Activity and Physical Fitness in Children and Adolescents
Malina (1996) defined tracking, or stability of a characteristic, as the maintenance of relative rank or position within a group over time. Ideally, long-term observations of the same individual on at least two occasions are needed. Studies that estimate the tracking of physical activity and fitness usually use correlations (Pearson or rank order) between the repeated measurements. Correlations < .30 are considered low and those between .30 and .40 are moderate. Recent studies suggest that physical activity in childhood is a determinant of physical activity in adulthood (Dennison et al., 1988; Raitakari et al., 1994; Pate, Baranowski et al. 1996; Janz, Dawson, & Mahoney, 2000; Twisk et al., 2000. Pate et al. (1996) determined whether physical activity behavior tracked during early childhood. Forty-seven children (22 males and 25 females) aged 3-4 years at the beginning of the study were followed over a 3-year period. These children were a subgroup of the participants (n = 263) of the Study of Children's Activity and Nutrition (Baranowski, Stone, & Klesges, 1993). Each subject had been observed on a minimum of two and up to four occasions from 3 p.m. to 6 p.m. during each of the 3 years of the study. Families participated in annual summer clinics at which various types of data were collected. Physical activity was assessed by measuring heart rate using a portable monitor. In addition, physical activity was quantified as the percentage of observed minutes during which heart rate was 50% or more above individual resting heart rate PAHR-50 index. For a given year, a child's physical activity was taken as the mean PAHR-50 index for the 2 to 4 observation days. Tracking of physical activity was analyzed using Pearson (r = 0.53 to 0.63, not significant) and Spearman rank order correlations (p < 0.0001, r = 0.57 to 0.66) correlations. The authors concluded that physical activity behavior tended to track during early childhood.
Raitakari et al. (1994) tracked physical activity of Finnish adolescents from 12 to 18 years of age. Information on frequency, duration and intensity of physical activity was derived from questionnaires completed by the students. A physical activity index was developed based on this information. The results of the study indicated that there were low to moderate correlations in habitual physical activity over a 3-year period (r = 0.33 to 0.35) as well as 6 years (r = 0.17 - 0.18), respectively. Moreover, Dennison et al. (1988) compared the physical activity level of 453 young men (23 to 25 years of age) and their physical fitness test scores during childhood (10 to 11 years of age) and adolescents (15 to 18 years of age). Physical activity was assessed by the Seven-Day Activity Recall questionnaire. Subjects recorded (to the nearest half-hour) the amount of time during the last 7 days spent in moderate, hard, and very hard physical activities at work and at leisure. Physical fitness was assessed by a battery of standardized schoolchildren tests including the 50-yard dash, standing broad jumps, sit-ups, pull-ups, shuttle run, and the 600- yard run. The results showed that active adults had better test results scores as children, specifically, the 600-yard run, the maximum number of sit-ups, 45-meter dash, and the shuttle run. Further, boys whose performances on the 600- yard run were below the 20th percentile were at greater risk for adult physical inactivity (40%) when compared with those who scored in the 80th percentile (23%). The authors concluded that fitness testing in boys might facilitate the identification of those at higher risk of becoming sedentary during adulthood.
Janz et al. (2000) investigated the tracking of physical fitness components (i.e., aerobic and muscular fitness) and two physical activity intensities (i.e., sedentary and vigorous) over a 5-year period from late childhood to adolescence. A total of 126 subjects (n = 61 males, aged 8 to 12 years; and n = 62 females, aged 7 to 11 years) all in pre- or early puberty, participated in the study. Maximal aerobic capacity was measured using direct determination of oxygen uptake (i.e., maximal stress test on a ergometric bicycle) and maximal grip strength was measured using a hand dynamometer (i.e., measurement for muscular fitness). Every 3 months sedentary physical activity was measured using a 1-day activity recall questionnaire. Participants reported the number of minutes he or she watched television and/or played video games. Similarly, vigorous physical activity also was assessed every 3 months using the 3-day Sweat Recall. Subjects reported the number of episodes (i.e., sports, games, play, work, or movement that lasted approximately 20 to 90 minutes) in which they were sweating or breathing hard due to physical activity for 20 minutes or longer. The results demonstrated that tracking of physical fitness and physical activity variables (i.e., peak oxygen uptake, heart rate, 3-day Sweat Recall, and TV/Video game recall) from late childhood through middle adolescence, tracked moderately well, with correlations ranging from 0.24 to 0.86 for males and 0.32 to 0.79 for females. In addition, sedentary behaviors tended to track better in boys (i.e., 73% of boys who were in the upper quartile--boys who watched more TV and/or played more games --for TV/video game recall remained there at follow-up) while there was a trend for the more physically active girls to remain active (note: this difference, however, was not statistically significant). The authors concluded that physical fitness and activity measures were moderately stable variables that tracked from childhood to adolescence. Thus, they suggested that early interventions should take place among children with sedentary behaviors.
Finally, Twisk et al. (2000) investigated the tracking of physical activity and physical fitness, as well as the relationship between physical activity, physical fitness and cardiovascular risk factors in 83 males and 98 females over a 15-year time period (i.e., 13 to 27 years of age). During the first 4 years of the study, yearly measurements were taken. A total of 6 measurements were taken with the last two measured at the age of 21 and 27 years, respectively. The amount of daily physical activity was measured with an interviewer who administered an activity questionnaire. This questionnaire addressed the total time spent on all habitual activities in relation to school, work, sports, and on other leisure time activities. Measured times were multiplied with the intensity of the different activities to calculate a total weighted activity score expressed as the number of metabolic equivalents (METs). Physical fitness measurements included tests for muscle strength, flexibility, speed of movement, coordination (neuromuscular fitness), and maximal oxygen uptake (cardiovascular fitness). Measurements of risk factors for cardiovascular disease included blood pressure, total serum cholesterol, and total body fatness (i.e., sum of four skinfolds including biceps, triceps, subscapular, and suprailiac).
The results indicated a low to moderate tracking for daily physical activity and maximal oxygen uptake (stability coefficient: 0.34 to 0.43), whereas good tracking was found for neuromuscular fitness (stability coefficient: 0.63 to 0.71). Thus, those who were in the lowest quartile of physical activity at the age of 13 years were 3.6 times more likely to remain in the lowest quartile along the measurement period of 15 years. Similarly, those who were in the lowest quartile for cardiovascular fitness at the age of 13 years were 4.4 times more likely to remain in this quartile. On the other hand, those who were in the lowest quartile for neuromuscular fitness at the age of 13 years were 14.2 times more likely to remain in this quartile over the period of 15 years. Moreover, daily physical activity was positively related to high-density lipoprotein cholesterol (HDL), p < .01, and inversely related to the total cholesterol: HDL ratio (p < .05) and to the sum of four skinfolds (p < .01). Cardiovascular fitness was also inversely related to total cholesterol (p < .01) while neuromuscular fitness was inversely related to the sum of four skinfolds (p < .01). The authors concluded that low tracking was observed for daily physical activity and cardiovascular fitness, whereas good tracking was observed for neuromuscular fitness. Also, the longitudinal development of physical activity and cardiovascular fitness were related to a healthier cardiovascular disease risk profile.
In summary, it appears that physical activity tracks at low to moderate levels during early adolescence into adulthood. Nonetheless, most studies emphasize the importance of tracking physical activity and physical fitness at early ages. Thus, by identifying children who do not meet the established guidelines for physical fitness and activity, successful behavior and intervention strategies can be established accordingly.
SUMMARY AND RECOMMENDATIONS
The current research clearly identifies the importance of physical activity and physical fitness to one’s health both in adults and children. However, taking into account the current low levels of physical activity and fitness among children, it is crucial that physical activity be promoted beyond the school and school day and into the home and community. A primary reason for promoting activity among children is that physical activity has the potential to track into adulthood (Dennison et al., 1988; Janz et al., 2000; Pate et al., 1996; Raitakari et al., 1994; Twisk et al., 2000). The goal is to instill in children the adoption of a physically active lifestyle that persists throughout adulthood. Children should be involved in physical activity programs, which emphasize exercise behaviors rather than outcomes (Council for Physical Education for Children, 1998). In addition, parents and physical educators should be aware of factors that may enhance the promotion of physical activity in children and how they can be facilitated. Currently, there are several national organizations including the Centers for Disease Control (1997) and the Council for Physical Education for Children (1998), who have provided guidelines on appropriate physical activity for children. The general consensus is that children should participate in moderately intense physical activity for most days of the week for 30 to 60 minutes.
Welk (1999) recently proposed a model of youth activity promotion to explain factors thought to influence physical activity in children. In brief, the model describes factors that are believed to predispose, enable, and reinforce activity behavior in children. For instance, predisposing factors first addresses the benefits versus the costs of participating in physical activity (i.e., is it worth it?). This question relates to the level of enjoyment a child may receive for participating in some form of body movement. Secondly, it addresses perception of competence. A child may be more likely to participate in an activity if he/she feels capable of performing the activity (i.e., am I able?). Enabling factors are those that enable a child to be active including access to a facility, physical skills and aptitudes, fitness level, and again a child's perception of his/her competence towards an activity. Finally, reinforcing factors are the variables that reinforce the child's interest in participating in physical activity (i.e., parents, peers, and coaches). Thus, it has been suggested that at a young age, children should be taught a variety of activities and physical skills, which in turn will enable them to find activities that they enjoy later in life. At the middle school level emphasis should be placed in mastering a specific skill and in high-school emphasis should be placed on behavioral skills such as self-monitoring, self-reinforcement, and program planning (Pangrazi et al., 1996). In summary, it is important to educate children about the benefits of being active as well as to instill in them the adoption of a physically active lifestyle that persists throughout adulthood.
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