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Psychosocial Correlates of Physical Activity in Healthy Children
Richard S. Strauss, MD;
Daria Rodzilsky, RD;
Gail Burack, PhD;
Michelle Colin, RD
Arch Pediatr Adolesc Med. 2001;155:897-902.
ABSTRACT
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Background Understanding the determinants of physical activity in children is critical
for the treatment and prevention of childhood obesity. Social-cognitive theory
has been used to understand behavioral patterns in children.
Objectives To explore the relationship between health beliefs, self-efficacy, social
support, and sedentary activities and physical activity levels in children
and to examine the relationship between physical activity and children's self-esteem.
Methods Ninety-two children aged 10 to 16 years completed the study. Physical
activity was monitored for 1 week with a motion detector (Actitrac; IM Systems,
Baltimore, Md). Moderate-level activity and high-level activity were defined
based on the results of treadmill testing. Health beliefs, self-efficacy,
social influences, and time spent in sedentary behaviors were determined through
questionnaires. Self-esteem was measured using the Piers-Harris Children's
Self-Concept Scale. Chronic anxiety was measured with the Revised Children's
Manifest Anxiety Scale.
Results There was a significant decline in physical activity levels between
ages 10 and 16 years, particularly in girls. Preteen girls spent approximately
35% more time in low- and high-level activity than did teenage girls (P<.001). Overall, children spent 75.5% of the day inactive,
with a mean ± SD of 5.2 ± 1.8 hours watching television, sitting
at the computer, and doing homework. In contrast, only 1.4% of the day (12.6
± 12.2 minutes) was spent in vigorous activity. Time spent in sedentary
behaviors was inversely correlated with the amount of moderate-level activity
(P<.001) but not high-level activity. In contrast,
time spent in high-level activity correlated with self-efficacy scores (P<.001) and social influences scores (P<.005). High-level physical activity was also associated with improved
self-esteem (P<.05). Higher health beliefs scores
were not correlated with physical activity levels.
Conclusions Children and adolescents are largely sedentary. Correlates of high-
and low-level physical activity are different. Time spent on sedentary activities
is inversely correlated with moderate-level activity, while self-efficacy
and social influences are positively correlated with more intense physical
activity. In addition, increased high-level physical activity is an important
component in the development of self-esteem in children.
INTRODUCTION
PREVIOUS RESEARCH has demonstrated that most children are largely sedentary.
Using data from the Muscatine Study, Janz et al1
found that pubertal and postpubertal children spend only 8 to 10 minutes per
day in aerobic activity. Livingstone and colleagues2
also showed that girls aged 7 to 15 years spend, on average, 8 to 10 minutes
per day in vigorous physical activity, while boys of the same age spend approximately
30 minutes per day in vigorous activity.
Determinants of levels of childhood physical activity are complex. Social-cognitive
theory involves analyzing the effects of parental and peer influences, child
beliefs, and personality on the adoption of a particular behavior, in this
case physical activity. It is now widely accepted that family, peers, and
school affect physical activity levels in children.3
Access to physical activities, such as the location of parks and schools,
and opportunities to participate in games or sports are also factors affecting
sports involvement.4 Similarly, parents who
play with their children regularly and provide transportation to activities
have more-active children.5 Personality characteristics,
such as achievement, motivation, self-confidence, independence, and one's
perceived ability to be active (ie, self-efficacy), are also associated with
physical activity levels.6, 7
It has also been suggested that physical activity, particularly sports
participation, may affect the development of self-esteem in adolescents.8 However, most previous studies have been limited by
including only small numbers of adolescents, no objective measurements of
physical activity, and outdated global self-esteem scores with no subscales.
Nevertheless, low to moderate correlations between self-reported physical
activity and global self-esteem in adolescents have been reported by Ferguson,7 Butcher,9 and Sherrill10 and their colleagues; however, neither Ferguson et
al nor Butcher specified which self-esteem scale was used.
The aims of this study, therefore, were to describe social and cognitive
factors associated with physical activity in children aged 10 to 16 years.
This study also aimed to further explore the relationship between sedentary
activities (such as television viewing) and physical activity, and the relationship
between physical activity and self-esteem in children.
SUBJECTS AND METHODS
SUBJECTS
Ninety-five of 96 consecutive healthy children between the ages of 10
and 16 years were recruited for the study between March 23 and June 12, 2000.
Children were recruited from suburban and urban families through the pediatrics
clinics at University of Medicine & Dentistry of New Jersey, New Brunswick,
and 2 work sites, representing mixed ethnicities and socioeconomic status.
Approximately 16 (17%) children were Hispanic or African American, 19 (20%)
were from single-parent families, and 20 (21%) had parents who were professionals.
Complete data were available on 92 children (44 boys and 48 girls). Informed
consent was obtained at the time of recruitment, and each family received
a stipend after completion of the study. Approval for the study was obtained
from the institutional review board of Robert Wood Johnson Medical School,
University of Medicine & Dentistry of New Jersey.
MEASUREMENT OF SOCIAL AND COGNITIVE FACTORS
Each child was asked to complete the children's physical activity questionnaire
developed by Saunders et al.11 This questionnaire
consists of 3 scales to measure psychosocial correlates of exercise in children
as young as 10 years: the Self-Efficacy, Social Influences, and Health Beliefs
scales (Table 1). Parents completed
questionnaires concerning the amount of time each child spent on sedentary
activities.
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Table 1. Items for Measuring Psychosocial Correlates of Behavior*
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MEASUREMENT OF PHYSICAL ACTIVITY
Levels of habitual physical activity were assessed with a biaxial accelerometer
(Actitrac; IM Systems, Baltimore, Md). The detector is approximately half
the size of a beeper and is worn on the child's waist. Previous pilot testing
had established a high correlation (r2>0.96)
between activity readings using this detector and those from other larger
triaxial motion detectors. Children were instructed to wear the monitor during
waking hours for 1 week. Acceleration was sampled 40 times a second and integrated
over 30-second intervals. Habitual physical activity levels were categorized
by units of acceleration based on treadmill testing during previous pilot
data collection (Table 2). Similar
cutoffs for physical activity levels have been previously reported.12 Because children spent minimal time in vigorous activity,
high activity and vigorous activity times were grouped together. Individual
activity levels and self-efficacy were further categorized as high or low
based on the 25th and 75th percentiles of the entire cohort, respectively.
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Table 2. Activity Levels Defined Using Motion Detector
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MEASUREMENT OF SELF-ESTEEM AND ANXIETY
The Piers-Harris Children's Self-Concept Scale and the Revised Children's
Manifest Anxiety Scale were used to assess self-esteem and anxiety. The Piers-Harris
Children's Self-Concept Scale is an 80-item standardized self-report inventory
designed to assess children's feelings about themselves.13
The Revised Children's Manifest Anxiety Scale measures chronic (as opposed
to acute situational) anxiety.14 Total anxiety
scores measured by the Revised Children's Manifest Anxiety Scale were correlated
with anxiety subscores measured in the Piers-Harris inventory (r = 0.82, P<.001), suggesting a high level
of consistency with the questionnaires.
DATA ANALYSIS
Data were analyzed using commercially available software (SPSS version
8.0; SPSS Inc, Chicago, Ill). Differences in continuous variables were assessed
using the independent t test or 1-way analysis of
variance. Differences in proportions were compared by means of  2 tests. Multivariate regression analysis was used to assess the effect
of social and cognitive variables and sedentary behavior time on physical
activity levels after controlling for age and sex. Logistic regression analysis
was used to determine the relationship between high and low levels of physical
activity and high and low levels of sedentary behavior and self-efficacy.
A small number of outliers greater than 3 SDs from the predicted models were
excluded.
RESULTS
Children spent a mean ± SD of 24.5% ± 6% of waking hours
in moderate- or high-level physical activity (Table 3). Sixteen percent of their time was spent in moderate-level
activity (ie, walking or playing), with vigorous activity constituting only
1.4% of waking time (mean ± SD, 12.6 ± 12.2 min/d). Children
spent 10.4 ± 0.8 hours per day relatively motionless. Overall, these
children spent 5.2 ± 1.8 hours per day doing homework, sitting at the
computer, or watching television, while the remaining 4.5 ± 0.7 hours
per day of sedentary time primarily were at school.
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Table 3. Child Characteristics*
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Physical activity levels were related to age and sex. Before age 13
years, similar levels of physical activity were present in girls and boys
(P = .43); however, after age 13, boys were significantly
more active than were girls (total activity time: 23.5% ± 4.7% vs 19.0%
± 3.8%; P<.05). Moderate- and high-level
activity decreased significantly between ages 10 and 16 years for both sexes
(Table 4). Among girls, overall
time spent at all physical activity levels was 35% higher in preteens compared
with that in teenage girls (P<.001).
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Table 4. Correlates of Physical Activity in Children Aged 10 to 16
Years
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Correlates of moderate- and high-level activity were different (Table 4). Time spent on sedentary activities
was inversely correlated with moderate activity. Children who spent the least
time participating in sedentary behaviors were significantly more likely to
have high levels of moderate activity compared with children who spent the
most time in sedentary behaviors (odds ratio, 9.14; 95% confidence interval,
1.53-55.00). In particular, television time (ß
= - .29, P<.01) and computer time (ß = -.29, P<.01)
were inversely correlated with moderate activity. Health beliefs, self-efficacy,
and social influences scores were not significantly correlated with moderate
activity. Multivariate regression analysis demonstrated that only age and
sedentary behavior time independently correlated with moderate activity levels
(r2 = 0.35, P<.001),
with approximately 10% of the variance in moderate activity explained by sedentary
behavior time.
Increased levels of high activity were primarily associated with increased
self-efficacy and social influences scores. Time spent on sedentary activities
was not correlated with high activity. Similarly, higher health beliefs scores
were not correlated with high activity levels. In contrast, all 3 measures
of self-efficacy were significantly correlated with high activity. Overall,
children with increased levels of self-efficacy were significantly more likely
to have increased levels of high activity compared with children with low
levels of self-efficacy (odds ratio, 4.07; 95% confidence interval, 1.03-16.30).
In addition, social influences scores were significantly associated with increased
high activity. Multivariate regression analysis demonstrated that age, sex,
and self-efficacy were significant independent correlates of high activity
(r2 = 0.29, P<.001),
with approximately 10% of the variance in high activity explained by self-efficacy
scores.
Mean ± SD Piers-Harris self-esteem scores were 58.3 ±
10.7, similar to previous findings.15 There
was no significant difference in total self-esteem scores between age (P = .42) and sex (P = .47). Similar
results were observed with each of the 6 self-esteem subscales. Behavior,
happiness, intellectual, and popularity self-esteem subscores were significantly
decreased in children with low levels of high activity (Table 5). In contrast, self-esteem subscores were not related to
moderate activity levels. In addition, neither anxiety score was related to
physical activity levels.
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Table 5. Physical Activity and Self-Esteem*
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COMMENT
Overall, children spent more than 10 hours each day sedentary. In contrast,
children were involved in vigorous physical activity only 12 to 13 minutes
per day. These data also demonstrate a significant decline in physical activity
as children progress through adolescence. In particular, girls have a significant
decrease in physical activity levels between ages 10 and 16 years. Similar
decreases in physical activity between the 6th and 12th grades have been previously
described in schoolchildren.16 Data from the
Youth Risk Behavior Surveillance System also demonstrated a significant decline
in physical activity among girls during high school.17
In 1977, Bandura18 first postulated that
behavioral changes were predominantly mediated by self-efficacy—the belief that one can successfully perform a desired behavior.
According to Bandura, "Efficacy expectations determine how much effort people
will expend and how long they will persist in the face of obstacles and aversive
experiences."18(p193) Self-efficacy measures
are tailored to assess specific behaviors. In this study, self-efficacy comprised
a child's belief in his or her ability to become physically active, even in
the presence of barriers to physical activity or alternative activities. As
such, self-efficacy was a major correlate of high-level activity in children.
Reynolds19 and Saunders11
and their colleagues also demonstrated that self-efficacy was significantly
correlated with self-reported levels of physical activity in adolescents.
In addition, Sallis et al20 have shown that
self-efficacy was the strongest correlate of exercise behaviors in a community
sample of adults. Therefore, programs that enhance children's beliefs in their
ability to exercise may actually increase motivation to be physically active.
In contrast, the health belief model postulates that the likelihood
of adopting a particular behavior is related to an individual's perception
that the behavior will either improve or damage his or her health.21 In this study, health beliefs about the benefits
of physical activity were not related to actual activity levels. O'Connell
and colleagues21 also demonstrated that the
health belief model was minimally associated with adolescents' exercise participation.
Similarly, Sallis et al20 showed that health
beliefs contributed only minimally to physical activity in a community sample.
These results are not surprising; after all, it is well-known that adolescents
frequently smoke cigarettes and consume alcohol and other drugs despite detailed
knowledge of the health detriments of these behaviors. Unfortunately, parents
and physicians tend to use the health belief model most frequently to get
children to be active, admonishing, for example: "If you exercise, you'll
lower your cholesterol." "The best way to lower your blood pressure is to
exercise." "If you're more active, you'll lose weight and have more energy."
Sedentary time was equally divided among viewing television, sitting
at the computer, and doing homework. It is no surprise that increased levels
of sedentary behaviors were associated with decreased levels of physical activity;
however, previous studies22, 23, 24
have tended to solely focus on television viewing as a marker for sedentary
behaviors. In this study, time spent on television viewing and computer activities
was equivalent, and both were inversely correlated with moderate-level physical
activity but not high-level physical activity. Therefore, children who spend
less time in sedentary behaviors will spend more time in moderate-level activity,
such as playing, while not necessarily participating in high-level activity,
such as sports. Data from the Bogalusa Heart Study indicate that increased
time spent watching television, using the computer, and playing video games
was not associated with decreased levels of high-level physical activity.25 Other data have also shown that television viewing
has only a weak, if any, association with high-level activity, such as brisk
walking, jogging, and running.26, 27
Therefore, the findings that less sedentary children have increased moderate-level
physical activity is important, because children spend a significantly greater
proportion of their time in moderate-level activity compared with high-level
activity, and moderate-level activity is particularly difficult to assess
by questionnaire. Therefore, increased levels of moderate activity may account
for the lower amounts of weight gain observed in children who limit television
viewing.28
In this study, high-level but not moderate-level physical activity was
associated with improved self-esteem scores. Positive associations between
physical activity and self-esteem in adolescents have been reported by Ferguson,7 Butcher,9 and Sherrill10 and their colleagues. Page and Tucker29
demonstrated that adolescents who rarely exercise are more likely to experience
loneliness, shyness, and feelings of hopelessness. In contrast, no relationship
was observed between physical activity levels and anxiety. In adults, exercise
must be prolonged and fairly strenuous to reduce anxiety.30, 31
However, increases in lactate levels from exercise may actually exacerbate
anxiety.32
Although surveys such as the Youth Risk Behavior Surveillance System
suggest that approximately half of adolescents participate in regular, vigorous
activity,33 studies using heart rate monitors
and doubly labeled water suggest that such reports overestimate physical activity.1, 2 Because questionnaires can be unreliable
in assessing physical activity in children, Saris34
and Rowlands et al35 have recommended an objective
assessment of activity in children, using an accelerometer, a heart rate monitor,
or doubly labeled water. Accelerometers have been extensively tested and validated
in children.36, 37 Investigation
using motion detectors with children demonstrated a high correlation (r = 0.86-0.88) between readings and observed physical activity,
independent of sex.38 In addition, significant
correlations exist between motion detector activity measurements and total
and sedentary energy expenditure.39
Although only a limited number of children were studied, the patterns
and levels of physical activity described herein are comparable to those of
other larger studies.1, 2 Increased
numbers of children and prospective studies are needed to provide understanding
of causal relationships between physical activity and psychosocial variables,
especially among subgroups of children such as minorities or children who
are obese. In a cross-sectional study, it is not possible to determine the
degree to which self-efficacy affects physical activity or the degree to which
physical activity affects self-efficacy. Nevertheless, these results provide
a conceptual framework for understanding physical activity levels in healthy
children, as the relationships of physical activity levels to psychosocial
variables and self-esteem were significant and consistent.
In conclusion, this study demonstrates that healthy children aged 10
to 16 years rarely engage in vigorous physical activity. Computer use is a
sedentary behavior that is becoming increasingly common and is associated
with lower levels of physical activity. To be most effective, interventional
efforts to increase physical activity should primarily target decreasing television
and computer time and increasing self-efficacy. In addition, increased levels
of physical activity are an important component in the development of self-esteem
in children.
AUTHOR INFORMATION
Accepted for publication March 16, 2001.
This study was supported by a Nestlé Nutrition Grant for Young
Investigators, sponsored by the Child Digestive Health and Disease Foundation,
Houston, Tex.
From the Childhood Weight Control Program, Division of Pediatric Gastroenterology
& Nutrition, Department of Pediatrics, Robert Wood Johnson Medical School,
University of Medicine & Dentistry of New Jersey, New Brunswick.
Corresponding author and reprints: Richard S. Strauss, MD, Childhood
Weight Control Program, Division of Pediatric Gastroenterology & Nutrition,
Department of Pediatrics, Robert Wood Johnson Medical School, University of
Medicine & Dentistry of New Jersey, One Robert Wood Johnson Place, CN
19, New Brunswick, NJ 08903-0019 (e-mail: strausrs{at}rwja.umdnj.edu).
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