More than one third of American teenagers today do not partake in
daily physical activity (National Center for Health Statistics, 2005;
Paluska & Schwenk, 2000). Furthermore, adolescent participation in
vigorous physical activity (defined by the CDC as physical activity for
at least 20 minutes on 3 or more days per week that induces sweating and
heavy breathing) declined over a ten-year period from 1993 to 2003
(Adams, 2006). In addition, adolescent participation in physical
education (PE) classes (a potentially significant source of regular
exercise for adolescents in the United States) dropped substantially
from 42% to 28% between 1991 and 2003 (Centers for Disease Control and
Prevention, 2006). These trends are concerning, since adolescence is an
important period for establishing life-long physical activity patterns
(Telama et al., 2005).
Physical inactivity accounts for 3.9% of worldwide deaths annually,
and accounts for a larger proportion of the disease burden in developed
countries such as the United States (Murray & Lopez, 1996). For
young people, increased rates of non-communicable diseases, including a
doubling in the number of overweight adolescents in the past 20 years,
are due in large part to sedentary lifestyles (Centers for Disease
Control and Prevention, 2006; Council on Sports Medicine and Fitness,
2006). Regular physical activity is a critical component of a healthy
lifestyle in adolescents because it can prevent the onset of serious
medical conditions including cardiovascular disease, obesity,
hypertension, and type 2 diabetes (Dehghan, Akhtar-Danesh, &
Merchant, 2005; Penedo & Dahn, 2005). In addition, regular physical
activity may be important to psychological well-being. A significant
amount of data suggest that physical activity is inversely related to
depressive symptoms and may help to mitigate the negative effects of
mood disorders in adolescents and adults (Paluska & Schwenk, 2000;
The World Health Organization estimates that mood disorders are the
second largest contributor to the global disease burden behind
cardiovascular conditions (National Institute of Mental Health, 2001).
Depression, currently the fourth leading cause of loss of productive
life-years globally, is expected to be the second leading cause by 2020,
surpassing tuberculosis, malaria, war, and HIV (Murray & Lopez,
1996). Kessler and Walters (1998) estimate that 33% of females and 20%
of males age 15 to 24 years in the United States have been depressed at
some point in their lives and suggest the problem is growing. Data from
recent birth cohorts indicates that the prevalence of depression is
highest among adolescents age 15 to 24 years declining monotonically
with age (Cross-National Collaborative Group, 1992). Depression is
occurring earlier than ever before in the United States (Cross-National
Collaborative Group, 1992).
Participation in physical activity and the associated effects on
mood are not well understood in rural adolescent populations. Physical
inactivity, however, is an acute problem among rural adult populations
and rural adolescents are at greater risk for psychological disorders
(Parks, Housemann, & Brownson, 2003; Peden, Reed, & Rayens,
2005). We know of only one published study that provides information on
the physical activity and PE class participation of rural adolescents
(Springer, Hoelscher, & Kelder, 2006). The study analyzed nationally
representative data from the Center of Disease Control Data Youth Risk
Behavior Survey in 2003. Results indicated that youth living in the
southern United States and in urban settings had lower physical activity
participation rates compared to youth in the western United States and
in rural settings.
There is also a lack of published studies on the effect of physical
activity on depressive symptoms in adolescents (Motl, Birnbaum, Kubik,
& Dishman, 2004). Only 2 published studies on this association used
non-clinically depressed samples and controlled for known confounders,
including socioeconomic status (SES) and some measure of general health
(Motl et al., 2004; Steptoe & Butler, 1996). One study employed a
longitudinal design and found that naturally occurring changes in
physical activity were negatively related to changes in depression
scores among 4,594 U.S. adolescents over a 2-year period (Motl et al.,
2004). The relation remained significant when the effect of confounding
variables such as gender and socioeconomic status was controlled for.
Another study found a positive relation between an index of sport and
vigorous activity and psychological well-being among 5,061 adolescents
in the United Kingdom, independent of the effect of gender, social
class, health status and use of hospital service (Steptoe & Butler,
1996). To date, no studies of the association between physical activity
and depressive symptoms have studied adolescents in U.S. rural settings.
The limited studies on the exercise pattern and mood disposition of
rural adolescents suggest that more empirical research on this topic is
The objectives of the present study were to 1) determine the
percentage of students in a medium-sized town (population 50,723) in
rural northwestern U.S. who exercised at or above the CDC recommended
level for adolescents; 2) report the percentage of students who achieved
this level of exercise through public high school PE classes; and 3)
confirm or refute the presumptive correlation between exercise and mood
state in a normative population of 9th and 10th grade high school
students adjusting for SES, self-reported health status, grade, age,
gender, and race.
Participants were 852 9th and 10th grade students from three public
high schools located in a rural area in northwestern U.S. The
students' average age was 14.8 years (SE = 0.024). Eighty-five
percent of the sample consisted of Caucasian students, 2.0% consisted of
Native American students, 0.85% consisted of African-American students,
2.0% consisted of Asian Pacific Islander students, 3.5% consisted of
Hispanic students, and 6.7% described their race as 'other.'
These proportions are within 1.5% of the estimated proportions of
Caucasian, Native American, African-American, Asian Pacific Islander,
and Hispanic youths between the ages of 10 and 19 in the county where
the study took place (US Census Bureau, 2004). Almost half (49.6%) of
the participants were freshmen (n = 423). Fifty-seven percent (57%) of
participants surveyed were female (n = 485).
All 9th and 10th grade students from the three high schools were
invited to participate. Parental consent and student assent were
obtained. The survey response rate was 47%. Twenty-four surveys (2.7%)
were excluded from the analysis due to incomplete data.
Zip code was used to classify the socio-economic status of
participants. Based on zip code, 52.1% of participants lived in an area
with a 'medium' median household income ([micro] =$37,197),
25.5% lived in an area with a 'high' median household income
([micro] = $42,403), and 22.4% lived in an area with a 'low'
median household income ([micro] = $27,547).
A 23-item questionnaire was designed to assess the physical
activity habits, mood, basic demographic information, and general health
state of 9th and 10th grade high school students. The first ten items of
the instrument comprised the Children's Depression Inventory
Short-Form (CDI-S;Kovacs, 1985). The CDI-S measures depressive symptoms
in children and adolescents ages 7 to 17 years. CDI-S raw scores range
from 0 to 20. Previous research suggests that the CDI-S is
psychometrically sound, with high internal consistency (Kovacs, 1992;
Mather & Cartwright-Hatton, 2004). In a non-clinical sample,
test-retest reliability coefficients for the CDI-S were acceptable,
ranging from 0.74 to 0.77 (Smucker, Craighead, Craighead, & Bean,
1986). Results from the CDI-S have been shown to be comparable to the
27-item long-form CDI from which it is derived (Kovacs, 1992). The CDI
long-form has shown good test-retest reliability, high concurrent
validity, and high internal consistency in clinical and non-clinical
samples (Brooks & Kutcher, 2001). In this study the Cronbach's
alpha coefficient for the CDI-S items was 0.84.
Four multiple-choice questions from the Center for Disease Control
2005 Youth Risk Behavior Survey (CDC YRBS) were used to assess the level
of vigorous and moderate physical activity of the students in the last
seven days and over the last 3 months (Gunbaum et al., 2004). The
definitions for vigorous and moderate physical activity used in this
study are based on national guidelines provided by the CDC (Gunbaum et
al., 2004). A single multiple-choice question from the YRBS was used to
assess participation in a PE class ("In an average week when you
are in school, on how many days do you go to physical education (PE)
classes?") The test-retest reliability for the nationally
administered YRBS as a self-report measure has been well established.
Previous research has shown that the YRBS physical activity items used
in this study, including the item on PE class participation, have
excellent test-retest reliability (Brener, Collins, Kann, Warren, &
Williams, 1995; Brener, et al., 2002;
Lowry, Wechsler, Kann, & Collins, 2001). In addition, previous
research suggests the YRBS definitions of vigorous and moderate physical
activity correlate well with physiological indicators of fitness,
suggesting construct validity (Prochaska, Sallis, Sarkin, & Calfas,
2000). In adolescents, the YRBS question on vigorous physical activity
has been shown to be highly correlated with actual vigorous exercise as
measured by an accelerometer even when the question is administered
independent of the other YRBS questions (Troped, et al., 2004). Overall,
self-reported physical activity levels by adolescents appear to be
reliable (Sallis, 1991).
Two multiple-choice questions modified from a previous study on the
association between physical activity and mood in adolescents were used
to assess the general health status of the students (Steptoe &
Butler, 1996). The first item asked respondents, "How many times in
the last 3 months have you been sick, injured, or felt sick for a period
of at least 2 days where your regular routine was interrupted?" The
second item asked respondents, "How many times in the last 3 months
have you been to the doctor's office, hospital, or any other
medical facility because you were unwell, sick, or injured?" Three
open-ended items (grade, age, and zip code) and two multiple-choice
items (gender and race) asked for respondents' demographic
information. The final question asked for respondents' weight and
height and was open-ended.
The principal investigator administered the survey in each
classroom using a standardized script of instructions and procedures.
Students had access to a tape measure and scale at all three high
schools to obtain their weight and height if necessary.
The proportion of males and females that exercised vigorously at or
above the CDC recommended level was compared using a logistic regression
analysis controlling for school, grade, race, SES, and the interaction
term gender by grade. Due to the low ethnic diversity in our population
the race of the participants was categorized as Caucasian or
'other', and this dichotomous variable was included in the
model. The proportion of males and females enrolled in daily PE classes
was also compared with the same variables using a logistic regression
analysis. Only variables with p values less than .05 were considered
significant and maintained in each model. The Hosmer-Lemeshow Chi-Square
test was used to evaluate each model's goodness-of fit.
The relationship between physical activity and CDI-S raw score was
evaluated using a multiple regression model. The response variable was
the CDI-S raw score. Physical activity and health were treated as
continuous variables. For highly correlated variables (i.e. the physical
activity questions and the health questions) only one variable was
included in the model. As a result, moderate physical activity
participation was described for the sample but excluded from the
analysis. Other variables included in the model were school, gender,
race, grade, and socioeconomic group. All possible two-way interaction
terms were initially included in the model.
Vigorous physical activity participation
On average, males and females exercised vigorously for 4.27 (SE =
0.126) and 3.34 (SE = 0.102) days per week, respectively (Table 1). 74%
of males and 60% of females reported exercising vigorously three or more
days in a week. 54.2% of female 10th graders and 74.7% of male 10th
graders met the CDC recommended level of exercise (Table 2).
Logistic regression analysis showed that only gender and grade
level were associated with adequate weekly vigorous exercise. Female
10th grade students exercised the least (see Table 2). After controlling
for grade, the odds of males exercising at the CDC recommended level
was, on average, 1.88 times greater than for females (OR = 1.88, 95% CI
= 1.40 - 2.53, Wald [chi square] = 4.17, p < .001). Ninth-grade
students were 1.35 times more likely to meet the recommended exercise
level compared to 10th grade students after controlling for the gender
effect (OR = 1.35, 95% CI = 1.01 - 1.82, Wald [chi square] = -2.05, p
< .05). The proportion of students that exercised at the CDC
recommended level was not significantly related to school, race, or SES.
The Hosmer-Lemshow statistic ([chi square] = 3.7, p = 0.15) indicated
the logistic regression model fit the data adequately.
PE class participation
Sixty-six percent of all students surveyed did not take a daily PE
class. Only 19.2% of females surveyed were enrolled in a daily PE class
compared to 45.8% of the males surveyed. Only 16.7% of 9th grade females
were enrolled in a daily PE class (Table 2). In contrast, 41.3% of 9th
grade males had a daily PE class.
Logistic regression analyses showed that race, grade, and gender
were all associated with enrollment in PE classes. After controlling for
grade and race, the odds of males being enrolled in a PE class was, on
average, 3.69 times greater than for females (Wald [chi square] = 8.28,
p < .01). Other factors that affected the probability of enrollment
in a PE class were grade level (Wald [chi square] = 2.24, p < .05)
and race (Wald [chi square] = 2.20, p < .05). Ninth-grade students
were, on average, 1.42 (95% CI = 1.05, 1.93) times more likely to be
enrolled in PE than 10th grade students. Caucasian students were, on
average, 1.60 (95% CI = 1.05, 2.43) times more likely to enroll in PE
compared to other races, controlling for gender. The proportion of
students taking a daily PE class did not differ significantly by school
or SES. The Hosmer-Lemeshow statistic ([chi square] = 0.604, p = 0.896)
indicated the logistic regression model fit the data adequately.
Seventy-five percent of the students reported being sick three or
fewer times in the past three months. The mean number of interruptive
events of illness in the past 3 months was 2.29 (SE = 0.082) for females
and 1.56 (SE = 0.082) for males (see Table 1). The median value for
interruptive events of illness was between 1 and 3 events at all three
Correlations were calculated among health status and physical
activity variables. Significant correlations were found among the
following variables: vigorous exercise completed over a week and
vigorous exercise completed over three months (r = .733, p < .01);
moderate exercise completed over seven days and over three months (r =
.649, p < .01); and events of illness over three months and clinic
visits over three months (r = .452, p < .01).
Depressive Symptoms (CDI-S scores)
CDI-S raw scores range from 0 to 20. The mean depression score for
all respondents in this study was 2.81 (SE = 0.111) (Table 1). Overall,
75% of CDI-S scores were below 4.00. The proportion of participants
scoring above the suggested clinical cutoff of eight points was 9.8%
(Schneider-Jamner, Spruijt-Metz, Bassin, & Cooper, 2004). The mean
raw score was 2.89 for females (SE = 0.14) and 2.69 (SE = 0.18) for
The multiple regression model used to explain variation in the
CDI-S depression score included the following variables: gender, school,
events of illness in the past three months, days of vigorous physical
activity in a week, and the interaction terms school by events of
illness, school by days of vigorous physical activity, and school by
gender. This model accounted for approximately 27% of the variation in
the mood score of students ([F.sub.11,839] = 29.5, p < .001) (see
Table 3). SES, grade level, race, and all other two way interaction
terms were not significant.
Each day of vigorous physical activity was inversely related to
mood. This relationship was not different between two of the high
schools, but had a significantly lower slope at the third high school
(see Table 3). At two of the three schools, females had lower mood
scores than males after adjusting for health status and physical
activity. At the third school, however, there was no difference between
males and females ([beta] = 0.04, p = 0.90). The number of events of
illness was positively associated with mood scores at all three schools
after controlling for gender and physical activity ([F.sub.1,839] =
140.65, p < .001); however, the relationship between health events
and mood was significantly different for the different schools (F2,839=
6.13, p < .001).
Approximately thirty-four percent (33.8%) of the participants did
not meet the CDC weekly recommended level for vigorous exercise of 20
minutes per day for at least 3 days in a week at the time of the survey.
Of the 66.2% of individuals that did meet the recommended level, only
43.1% were enrolled in a PE class at their high school (also see Table
2). The percentage of students taking part in some form of physical
activity and the overall percentage of students enrolled in a PE class
in this study were consistent with data collected at the national and
state level for the 2003 YRBS (Grunbaum et al., 2004; Idaho Department
of Education, 2003).
Males were more likely than females to exercise vigorously and
participate in daily PE in this study, a finding consistent with
previous studies in rural and non-rural adolescents (Gordon-Larsen,
McMurray, & Popkin, 2000; Springer et al., 2006). Ninth graders were
more likely than 10th graders to exercise vigorously and participate in
daily PE. Data from one recent study suggests older adolescents are less
likely to participate in all forms of physical activity than their
younger peers (Gordon-Larsen et al., 2000). Our results may be a
manifestation of this trend. It appears that adolescent choices on
physical activity participation are correlated with a number of
interrelated psychosocial factors such as self-efficacy (i.e.,
confidence in one's ability to be physically active) and influences
of family and friends on physical activity (Strauss, Rodzilsky, Burack,
& Colin, 2001). These factors may explain the developmental
differences reported here.
Additionally, the differences between the two grade levels may be
due to differences in curriculum requirements. For instance, schools may
require students in higher-grade levels to devote more time to academic
work. To the best of our knowledge, the requirements for both grade
levels were very similar in all three schools we studied. A systematic
analysis of curriculum requirements and psychosocial factors associated
with physical activity is beyond the scope of this study. However, such
information is very important for future studies focusing on
developmental differences in physical exercise.
Exercise patterns developed during adolescence often carry over
into adulthood, highlighting the importance of introducing young people
to regular physical activity (Telama et al., 2005). Participation in
free PE classes in the public school system is one way to ensure that
young people achieve the recommended level of exercise regardless of
their socioeconomic status, and perhaps develop a liking for physical
activity that remains with them later in life. The results of this study
suggest that certain groups of rural adolescents (females, 10th grade
students, and nonCaucasian students) are not enrolling in PE in numbers
equal to their peers. Particular attention should be given to female
participation since physical activity interventions administered through
PE classes have shown promise in increasing physical activity
participation rates in females (Schneider-Jamner, Spruijt-Metz, Bassin,
& Cooper, 2004). The percentage of females enrolled in a PE class in
this study was surprisingly low (19.2%), especially for 9th graders
Of the females that exercised at or above the CDC recommended level
for vigorous exercise, only 27.7% were enrolled in PE, compared to 59.6%
of males. This suggests that more female students achieve the CDC
recommended activity level by exercising outside of school compared to
male students. This finding suggests that females of lower socioeconomic
groups, who may not be financially able to enroll in extracurricular
activities outside of the school curriculum, may be at a disadvantage
for meeting the CDC recommended level of exercise. A trend suggesting
fewer of the females in the lower socioeconomic group met the CDC
recommended level of exercise was observed in this study. However, this
difference was not statistically significant when gender and grade level
were included in the logistic regression model, and this socioeconomic
disparity was not apparent in the male students.
The lack of a relationship between SES and exercise in this study
may have been due to the method we used to classify the socioeconomic
status of individuals. The zip-code data we used probably does not
capture true SES well in a medium-sized town. A more thorough
investigation into the relationship between SES and exercise in female
adolescents is critical, given the low enrollment of females in free PE
classes in this study, and findings from other studies that suggest
adolescents from lower socioeconomic backgrounds have significantly
higher rates of physical inactivity compared to wealthier individuals
(Gordon-Larsen et al., 2000).
Among the physical benefits of exercise, several studies have
demonstrated a positive association between physical activity and mood
in adolescents (Motl et al., 2004; Steptoe & Butler, 1996). To the
best of our knowledge, this is the first study to corroborate this
association in a rural sample of non-clinically depressed adolescents.
Although a cross-sectional study design was used to collect data on the
level of physical activity and mood of the students, thus limiting the
causal interpretation of the relationships detected in the study, the
data of this study corroborates the previously published association
between activity and mood. Individuals who exercised more had lower
scores on the depression index. Most students in this study (90.2%) had
mood scores within the normative range; however, those who exercised
regularly had moderately lower scores on the CDI-S, indicating a lower
tendency for depressive symptoms, a finding consistent with other
studies (Allison et al., 2005; Delahanty, Conroy, & Nathan, 2006;
Yeung, 1996). Also consistent with previous studies were the findings
that only vigorous exercise was associated with mood and that a greater
number of interruptive events of illness was correlated positively with
mood scores that reflected increased depression (Steptoe & Butler,
Interestingly, the mean raw mood score for females was not
statistically different from males (Table 1). However, after adjusting
for health events, school, and physical activity, females had, on
average, lower depression scores than males. The relationship between
mood and exercise among females highlights another reason to further
investigate the low level of exercise in females reported in this study.
Replication of the current finding is necessary. More data on physical
health, physical activity, academic curriculum and mental health status
of adolescents may help us understand the possible gender differences on
the relations between mood and exercise.
The response rate in this study was only 47%, and proportionately
more females participated in the survey. Although response bias from
students refusing to participate may have skewed the results of this
study, it is unlikely that it had a large effect, given that the level
of activity reported by the students and the mean CDI-S scores were
consistent with other surveys and with national averages (see Tables 1
and 2) (Gunbaum et al., 2004; Kovacs et al., 2003). Furthermore, the PE
class participation of 9th and 10th grade students reported in this
study was within 5% of the actual 2005 school district enrollment rates
for females and within 3% for males, suggesting the sub-sample of
students was representative of the school population.
Although self-reported levels of physical activity and mood are
reliable, they can be biased by a number of factors, including the
setting in which the survey was administered and culturally acceptable
perceptions of physical activity and depression (Sallis, 1991).
Respondents may have overestimated the amount of time they participated
in physical activity. To determine the consistency of responses provided
by the students, correlations between 7 day and 3 month vigorous and
moderate physical activity questions and between the two health status
items were obtained and were significant. Internal consistency for the
10 CDI-S items as determined by a Cronbach's alpha coefficient was
high (.80) and consistent with the range of alpha coefficients (.71 to
.89) obtained in previous research with the CDI-S (Kovacs et al., 2003).
Health status in our analysis was determined by one self-reported
item measuring the number of events of illness. The reliability and
validity of this item is unknown. However, the finding that events of
illness were significantly associated with increased depression scores
was consistent with previous research (Steptoe & Butler, 1996).
Further, as with the similar physical activity variables, the two health
status items were significantly correlated. All of these findings
indicated that students responded consistently on similar questions.
Furthermore, of the individuals that claimed to attend a PE class, 92.7%
claimed to exercise vigorously at least three days per week over the
last three months. The latter suggests that students were consistent in
responding to the exercise questions on the survey.
Finally, the small number of items used to measure physical
activity and illness is another limitation of the study. Although we
believe the items are good measures of the variables that we are
interested in, future studies should include a larger number of items,
In summary, 26.9% of our respondents reported no participation in
adequate vigorous or moderate physical activity. Of particular concern,
rural female adolescents reported significantly lower levels of vigorous
physical activity and lower daily PE class participation compared to
males. Females also had, on average, higher scores on the depression
index, which appeared to be due, in part, to lower exercise levels. High
school curricula that encourage physical activity programs and PE
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Acknowledgements: We would like to thank all participating students
as well as the faculty and staff from each of the three participating
high schools for their willingness to engage in the study. We would also
like to thank the administrators of the school district for their
cooperation. This project was supported by a faculty start-up grant
awarded to Dr. Sophie St.-Hilaire from the Office of Research at Idaho
State University and a faculty research grant awarded to Dr. Maria Wong
from the WeLEAD program at Idaho State University.
Sophie St-Hilaire, Maria M. Wong, and Teri Peterson
Idaho State University
Century High School
Author info: Correspondence should be sent to: Maria Wong, Ph.D.,
Dept. of Psychology, Idaho State U., Stop 8112, Pocatello, ID 83209.
TABLE 1 Mean Values for Selected Variables
Overall Male Female
M (SE) M (SE) M (SE)
Age 14.81 (0.024) 14.84 (0.038) 14.79 (0.031)
CDI-S score 2.81 (0.111) 2.69 (0.183) 2.89 (0.138)
Vigorous PA (a) 3.74 (0.081) 4.27 (0.126) 3.34 (0.102) ***
Moderate PA (b) 3.29 (0.073) 3.32 (0.111) 3.27 (0.095)
Events of illness (c) 1.98 (0.059) 1.56 (0.082) 2.29 (0.082) ***
Abbreviations: PA, physical activity; M, mean.
(a) Physical activity for at least 20 min that made them sweat/
breathe hard on 3 or more of past 7 days. (b) Physical activity for
at least 30 min that did make them sweat or breathe hard for at
least 30 min on 5 or more of past 7 days. (c) Events of illness in
past 3 months for at least 2 days that interrupted their regular
*** Independent samples t-tests comparing male and female showed
that the two groups were significantly different on vigorous
physical activities (t(850)= 5.76, p < .001) and events of illness
(t(849)= 6.17, p < .001). The two groups were not significantly
different on age (t(850)= 1.19, p = .23), CDI-S scores (t(850)=
.91, p = .36) and moderate physical activity (t(850)= 0.28, p =
TABLE 2 Percentage of Students Participating in Various Physical
Activity Related Behaviors at CDC Recommended Amounts
9th Grade 10th Grade 9th Grade
Vigorous PA (c) 73.5 74.7 66.7
Moderate PA (d) 38.1 36 30.8
Daily PE (e) 41.3 50.6 16.7
Daily PE and 39.15 49.4 15
vigorous PA (f)
Female Idaho (a) U.S. (b)
Vigorous PA (c)
54.2 66.4 64.6
Moderate PA (d)
36.3 29.5 25.5
Daily PE (e)
21.5 29.5 32.2
Daily PE and
vigorous PA (f) 18.3 -- (g) 41.9
Abbreviations: PA, physical activity; PE, physical education class.
(a) Data reference: Idaho Department of Education, 2003. (b) Data
reference: Centers for Disease Control, 2004. (c) Physical activity
for at least 20 min that made them sweat breathe hard on 3 or more
of past 7 d. (d) Physical activity for at least 30 min that did make
them sweat or breathe hard for at least 30 min on 5 or more of past
7 d. (e) Enrolled in a daily physical education class. (f) Enrolled in a
daily physical education class and vigorous physical activity on 3
or more of past 7 d. (g) This proportion was not available for Idaho
TABLE 3 Parameter Estimates for Significant Variables in the
Parameter B SE T
-.588 .073 -8.029 **
Vigorous PA (a)
.928 .094 9.928 **
Events of illness (b)
-1.965 .574 -3.421 **
School = C
-.021 .663 -.031
School = H .039 .323 .121
School C*Female -1.001 .389 -2.570 **
School H*Female -1.054 .338 -3.116 **
School P*Female .412 .098 4.199 **
School C*Vig PA (a)
.087 .107 .806
School H*Vig PA (a) -.246 .131 -1.881
School C*illness (b)
-.506 .145 -3.487 **
School H*illness (b)
Note. Dependent variable is total CDI-S mood score. Adjusted
[R.sup.2] = 0.27. Abbreviations: PA, physical activity; [beta], beta
coefficient of association. (a) Physical activity for at least 20
min that made them sweat breathe hard on 3 or more of past 7 d. (b)
Events of illness in past 3 months for at least 2 days that
interrupted their regular routine. (c) This parameter is set to 0
because it is redundant. ** p < 0.01