Pediatric Exercise Science, 1991, 3, 28-42
A Developmental Analysis
of Gender Didferences
in Health Related Physical Fitness
Jerry R. Thomas, Jack K. Nelson, and Gabie Church
Data for the analysis were the health related fitness scores, anthropometric
measures, and physical activity information from the National Children and
Youth Fitness Study. The subjects were 6,800 boys and 6,523 girls, ages 6
through 18. Multiple regression produced linear composites that were used
as covariates to evaluate physical and environmental characteristicsthat relate to gender differences. The distance runs, chin-ups, and sit-ups displayed
similar patterns in gender differences across age. Before puberty the important covariates are mainly physical, namely skinfolds. Following puberty
the major factors that reduce gender differences are skinfolds and the amount
of exercise done outside of school time.
Motor performances and fitness performances of boys and girls have been
compared in numerous studies. Thomas and French (19) comprehensively reviewed gender differences in motor performance across age. Most fimess performances of boys improve linearly from age 6 through 17-18. For girls there is a
linear increase from age 6 to about 14 or 15 (15). Boys score higher on tests of
strength, endurance, running, and jumping (4, 5, 12). Gender differences are
smaller in preschool and early elementary years. However, the increased size
and strength of boys provides a distinct advantage in most fitness measures after
puberty (10).
Thomas and French (19) suggested that environmental factors are primarily
responsible for gender differences in most motor performance tasks prior to
puberty. For example, parents and teachers expect certain types of sex role behaviors, and boys and girls are treated as though they should perform motor tasks
differently (18). From a physiological basis, the faster skeletal maturation in girls
prior to puberty suggests that their motor performance should actually be better.
The fact that it is not argues for a sociocultural explanation.
J.R. Thomas is with the Dept. of Exercise Science and Physical Education at
Arizona State University, Tempe, AZ 85287. J.K.Nelson is with the Div. of Teacher
Education at the University of Idaho, Moscow, ID 83843. G. Church is with the Dept.
of Experimental Statistics at Louisiana State University, Baton Rouge, LA 70803.
Gender Differences in Physical Fitness
- 29
Hall and Lee (8) reported evidence that differences in AAHPERD Youth
Fitness Test (1) scores between boys and girls in Grades 3,4, and 5 were smaller
when girls were given equal opportunity to learn and perform fitness activities.
Findings from the National Children and Youth Fitness Study I and II(16,
17) show that boys consistently outperform girls on all fitness measures except
flexibility from ages 6 through 18. Environmental influences on gender differences prior to and following puberty are unclear. It can be argued that if parents
and teachers consider gender differences in fitness and motor performance as
being biological (18), differences in treatment will be perpetuated. On the other
hand, not all of the gender differences in physical performance prior to puberty
can be attributed to environmental influences. Few studies have quantified the
comparative influences of physical growth and environment on motor performance differences. In a study on gender differences in throwing performance of
kindergarten children, Nelson et al. (14) reported that physical variables accounted for a significant portion of the variance. When physical variables were
not considered, the girls' performance was only 57% of that of boys. However,
when throwing performance was adjusted for physical variables, the girls' relative performance increased to 69 % of that of the boys.
This study evaluated the contributions of physical and environmental variables, measured in the National Children and Youth Fitness Study I and 11, in
explaining gender differences in health related physical fitness test performance
across ages 6 to 18. Specifically, this study focused on the mile run (or half
mile), sit-ups, chin-upslpull-ups, and sit-and-reach as these are influenced by
physical characteristics of height, weight, waist size, and skinfolds, and such
environmental variables as activity patterns and influences associated with the
school, community, and home.
Method
This study was a secondary analysis of data from the National Children and
Youth Fitness Study (NCYFS) initiated by the Office of Disease Prevention and
Health Promotion of the U.S. Public Health Service. The first part of the study
dealt with children in Grades 5 through 12 (essentially ages 10-18) and the
second phase included children in Grades 1 through 4 (ages 6-9).
In both parts of the NCYFS, the major emphases were to determine by
normative survey the health related physical fitness status of American children
and youth, to describe patterns of participation in physical activity in the schools
and community, and to examine the relationship of the activity patterns and the
influence of school, home, and community on the measured fitness performance.
Thus the NCYFS (I
and 11) involved fitness testing, anthropometric measurements, and a questionnaire survey of children (NCYFS I), parents, and teachers (NCYFS I . ) . Reports of NCYFS Phases I and I1 have been published in the
January 1985 and NovemberlDecember 1987 issues, respectively, of the Journal
of Physical Education, Recreation and Dance (JOPERD). The methodology is
described in detail in these two reports. Consequently, we will provide only a
limited description of the measurements of the variables used in this study.
Subjects
In this study, NCYFS I and 11data on 13,323 boys and girls 6 to 18 years of age
30
-
Thomas, Nelson, and Church
were used. Children younger than 6 and older than 18 were excluded. Table 1
provides means and standard deviations for height and weight and the numbers
of boys and girls at each age level. A total of 6,800 boys and 6,523 girls comprised the samples for this study.
Fitness Variables
This study considered four fitness measures: sit-and-reach, sit-ups, chinning,
and a distance run. All subjects were tested in the same manner in the sit-andreach and in the sit-ups. For the chinning performance, the younger children
(6-9 yrs) were tested on a modified pull-up test, and the distance run for the 6and 7-year-olds was a half mile as opposed to the 1-mile run for older subjects.
A team of trained testers administered the items with assistancefrom the teachers.
Most of the testing was done on a one-to-one basis. The measures used are
standard physical fitness field tests. Information pertaining to the validity and
Table 1
Demographic Data of Subjects
Height (in.)
Age
Gender
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
Boys
Girls
N
M
Weight (Ib)
SD
M
SD
Gender Differences in Physical Fitness
- 31
reliability of each test is provided in measurement texts such as Johnson and
Nelson (11) and in the quality control procedures described in the original
references.
Sit-and-Reach. The NCYFS used the sit-and-reach test from the health
related physical fitness test battery of the American Alliance for Health, Physical
Education, Recreation and Dance (2). This test requires an apparatus for measurement that was supplied by the NCYFS. From a sitting position with stockinged feet against the apparatus and keeping the knees straight, the child reaches
forward as far as possible. The measurement is in inches.
Bent-Knee Sit-ups. The subject lies on an exercise mat with arms crossed
and flat against the chest; knees are bent and a partner holds the feet in place.
The subject curls up to touch the forearms to the thighs and returns to the down
position as many times as possible in 60 seconds.
Chin-ups. The NCYFS supplies a door frame chin-up bar for this test.
In chin-ups the palms are facing the subject. The maximum number of correct,
continuous repetitions constitutes the score.
Modified Pull-ups. This test, which was given to the younger children
(ages 6-9), requires an apparatus that includes a rack and an adjustable bar. The
subject begins in a supine position, with only the heels in contact with the floor,
and pulls up as many times as possible to a level 7 to 8 inches below the bar.
Mile WalWRun. The mile run was the only test that was administered in
groups (of six or less), with partners assigned to cross off the number of laps and
record the time in minutes and seconds that was called out as the partner's runner
crossed the finish line. For younger children (ages 8-9), the counting of laps was
done by a second test administrator.
Half-Mile WalWRun. For children 6 and 7 years of age the half-mile waW
run was used. A test administrator kept track of the number of laps and recorded
the finishing times.
Physical Growth Variables
In addition to height and weight, other physical characteristics included waist
circumference, body mass index (Quetelet's Index), and skinfold thickness
(6,13). In Part I of the NCYFS, two skinfolds were taken: the triceps and subscapular. For the younger children the medial calf was also measured. Thus three
sums were considered in our study: triceps and subscapular, triceps and medial
calf, and the sum of all three skinfold measures.
The skinfold measurements in the NCYFS were taken by the trained field
staff specialists and are described in the Summary Reports, JOPERD, 1985 and
1987 (15, 16). Lange calipers were used with three measures taken at each site.
Interrater reliability was established both prior to and during field work. The
correlation coefficients for sum of skinfolds were high, ranging from .93 to .98
during training and between .93 and .99 in the field.
Environmental Variables
The NCYFS also endeavored to gather information that might shed some light
on the status of the measured fitness. In Part I the students fdled out a survey on
frequency, duration, and seasonality of exercise, sports, and games provided
through their physical education classes, other school programs, community organizations, and home or neighborhood. In the NCYFS-11, information was also
32
- Thomas, Nelson, and Church
obtained from the parents as to their activity habits and the extent to which they
engaged in physical activity with their children. The parents were also asked to
evaluate the activity levels of their children and the amount of time their child
spent watching television.
The reader is referred to the Summary Reports, JOPERD, 1985 and 1987
(15, 16), for a comprehensive discussion of the information that was gathered
about physical activity habits in the school, community, and home that might
affect the measured fitness status of the children. While neither of the NCYFS
studies verified the self-report data on physical activity of childrenlparents, most
values were within normal ranges. In addition there was moderate agreement
between parents' and teachers' evaluations of children's degree of physical
activity.
This study included only those environmental items that should logically
help explain gender differences in fitness performance. Thus items such as
"teacher beliefs about fitness testing" and "percent of students receiving fitness
awards" were not included. Examples of the types of information gathered
through the survey of students, parents, and teachers are shown in Table 2. Phase
Table 2
Variables Used in Analysis
Type of variable
Fitness:
Sit and reach (in.)
Bent knee sit-ups (no. in 60 sec)
Chin-ups (no. completed)
Modified pull-ups (no. completed)
Mile walklrun (min & sec)
Half-mile walklrun (min & sec)
Biological:
Height (in.)
Weight (Ibs)
Body mass index
Waist circumference
Sum of triceps & subscapular skinfolds (mm)
Sum of triceps & medial calf skinfolds (mm)
Sum of triceps, subscapular, & calf skinfolds (mm)
Age level
All
All
10-18
6-9
8-18
6-7
All
All
All
All
All
6-9
6-9
Environmental(examples of types of information obtained):
Amount of time spent in P.E. - wkslyear, dayslwk, minlwk, etc.
No. &types of P.E. activities
Outside of school (e.g., community) activities as to no. and frequency of participation
Fitness testing practices in school
Amount of time engaged in high-intensity activities in P.E. and outside of school
Ratings of child's activity by parents and teachers
Activity level of parents
Gender Differences in Physical Fitness
- 33
I1 had data on many more environmental variables than did Phase I. Very little
of the information in the two parts of the NCYFS was the same, thus it was not
possible to compare various environmental influences on fitness across all ages.
Analysis
Intercorrelations and backward selection multiple regression was calculated for
each fitness measure using linear composites of physical and environmental variables as predictors. Each linear composite was used as a covariate adjustment in
a subsequent ANCOVA model to evaluate physical and environmental characteristics that might influence gender differences. Unadjusted (ANOVA) and adjusted (ANCOVA) effect sizes were calculated and plotted to illustrate the
comparativeperformances of boys and girls and any reductions in gender differences when physical and environmental influences were taken into consideration.
Results
Intercorrelationswere calculated within age level among all the fitness, physical,
and environmental variables listed in Table 2. Since each age level had very large
Ns, it seemed more appropriateto set an absolute level of r that had some meaning
rather than using a standard level of alpha (e.g., -05 or .01); we selected r = .lo,
as this accounted for at least 1% of the variance.
Within each age level, four backward selection multiple regressions were
calculated, one for each fitness measure using physical and environmental variables as predictors (gender was not included in the regression models). Predictors
were dropped out of the equation according to the least contribution to l?, with
the process stopping when all remaining predictors had a semipartial r of 0.10
or greater. Some predictors were highly related to other predictors (e.g., sum of
three skinfolds and sum of two skinfolds). In these instances only one predictor
was used in the multiple regression procedures.
Multiple Regression
Mile Run. Although significance may not be a meaningful assessment
with such large numbers of subjects at each age level, a linear composite was
develo d at every age which was significantly (p<.01) related to the distance
run.
(variance accounted for by the linear composite) ranged from 0.20 to
.36, with the exception of an @= . l l for 10-year-olds. There was a tendency for
the R~ to be larger at 13 to 18 years of age (.27 to .36) than at 6 to 12 years of
age (only one was above .30).
The sum of skinfolds was the only physical variable significantly contributing to the prediction of the mile run. It was the most important characteristic for
prediction at every age level. The standardized regression coefficients (r) ranged
from .28 to .58. The positive coefficients mean that children 6 to 18 years of age
with large skinfolds run the mile (or half-mile) more slowly.
Environmental variables that contribute to the relation are in three general
categories: (a) Intensity of exercise-from 10 to 18 years of age, at least one
reflection of intensity of exercise (sweating and breathing hard, top five highintensity physical education activities, or number of other high-intensity physical
activities) was always related to mile-run performance (r ranged from - .06 to
.37). A negative loading reflects a positive relationship, high intensity, and lower
lr
34 - Thomas, Nelson, and Church
"-A
-
mile-run time. (b) Organized activities-at 7, 8, and 9 years of age, the number
of community activities was related to distance run performance (r = - .08 to
-.15), while at 11, 12, and 14 years of age the total number of organized
activities of high intensity was related to mile-run performance (r = - .06 to
- .07). In both instances, more activities was positively correlated to better performance. (c) Physical education-the relation of physical education to distancerun performance varies by age. At 6 to 7 years of age, having a physical education
specialist was related to improved performance (r = - .10 to - .12). At 6 to 9
years of age, however, enrollment and amount of physical education was related
to poorer performance (r = .09 to .20). Thus, with younger children, just having
physical education was not enough; it had to be taught by a specialist. At 12 and
at 14 to 18 years of age the amount of physical education was positively related
to the mile run (r = - .07 to - .14). At these ages physical education is nearly
always taught by a specialist.
Sit-and-Reach. This measure of lower back flexibility was inconsistent
in its relation to the physical and environmental variables assessed in the NCYFS
studies. No significant relationships were found for 5 of the 13 ages (6,7,9, 12,
17 years of age) and the R2s were very low (.02 to .lo) at the other age levels.
The regression coefficients were low and varied with age and the measure. In
view of the very low P s , little meaning could be attached to the small and
inconsistent relationships of the characteristics.
Sit-ups. This measure of abdominal strength and endurance was significantly related to a linear composite of physical and environmental variables at
all age levels. The R2s were moderate, ranging from .09 to .27. There were no
consistent age related changes in R2.
Sum of skinfolds was the most important predictor (r = - .23 to - .44) in
the linear composite at 12 of the 13 ages, and was second at age 11. At the
younger ages of 6 to 9 years, weight had a significant regression coefficient (r
= .09 to .17). However, around the onset of puberty at 10 to 12 years of age,
no other physical variables besides skinfolds were important. After the onset of
puberty (for most children), ages 13to 18 years, weight again becomes important
(r = .13 to .31), with height and body mass index occasionally being included.
Basically, heavier children with a smaller sum of skinfolds can do more sit-ups.
This probably reflects a more muscular body build.
Environmental variables that were predictive of better sit-up performance
were physical education (amount and intensity) and community sport activities
(amount and intensity). Although the standardized regression coefficients were
not large (r = .08 to .28), at each age (except 6 yrs) several of the environment
variables were important.
Chin-ups (Modified Pull-ups for Ages 6-9). This test reflects arm and
shoulder strength and muscular endurance and was significantly related to a linear
composite of physical and environmental characteristics at every age. ranged
from .08 to .47 and increased across age.
Sum of skinfolds was the best predictor at every age (r = - .15 to - .77)
and also became more important with increased age. Weight is a second physical
characteristic related to chin-up performance (r = .14 to .45). Finally, height is
related to chin-up performance in one way at ages 6 and 8-12 (r = - .08 to
-.23), and in another way at ages 14 and 15 (r = .08 to -17). Basically, for
younger and mostly prep~bertal~children,
better performance isas
Gender Differences in Physical Fitness
- 35
a short but muscular body build. For the older children there was a tendency for
taller but more muscular ones to perform better.
Beginning at about 8 years of age and continuing through high school,
environmental variables that are positively related to chin-up performance are
those that reflect high-intensity exercise. Occasionally a few other environmental
characteristics are included, but they do not show up regularly or with high
loadings.
Gender Differences
In order to evaluate gender differences, we calculated four ANOVAs for each
age, one for each health related physical fitness test. In Table 3 under the "unadjusted" columns, the means for boys and girls and the F ratios are reported by
age and fitness test. Also included is an effect size (ES), which represents the
standardized difference between boys and girls (mean for boys minus mean for
girls, divided by the pooled standard deviation) (20). Effect size can be judged
by absolute size: .2 = small, .5 = moderate, .8 = large.
To evaluate how the linear composites of predictors established in the
Multiple Regression section might influence gender differences, we calculated
ANCOVAs by age and fitness test using the linear composites as covariates for
each test. These results are reported under the "adjusted" columns in Table 3
and include the adjusted means for boys and girls, adjusted Fratios, and adjusted
ES based on the adjusted means and pooled standard deviations. Figure 1 presents
a clearer picture of the differences between unadjusted and adjusted ES across
age. Curves above 0 indicate better performance by the boys while curves below
0 represent better performance by the girls.
Mile Run. Unadjusted differences (difference between the means, F ratios, and ES) generally became larger, with boys performing better with increasing age. Absolute differences in performance reached 2 minutes (ES=0.90) at
11 years of age and 3 minutes (ES= 1.36) at 15 years of age. Adjustments for
the linear composite of covariates reduced the differences at every age level,
with the largest reductions at 6 to 8 years and at 13 to 18 years. Reductions were
smallest around puberty (see Figure 1).
Sit-and-Reach. Unadjusted gender differences for the sit-and-reach were
significant, with girls showing more hamstring and lower back flexibility than
boys at every age. The differences increase from about 1 in. (ES= -0.50) in
early childhood to about 2 in. at puberty (ES= - 1.0) but are reduced slightly at
17 and 18 years of age (ES= -0.60). Slight adjustments are made by use of the
linear composite as covariates in ANCOVAs at 7, 8, 9, and 16 years of age.
However, these adjustments are so minor that they lack any meaning.
Chin-up (Modified Pull-ups for Ages 6-9). Unadjusted values for pullups are not significantly different for boys and girls at 6 years of age, but beginning at age 7 the differences become reliable and continue to increase steadily
across childhood and adolescence. Absolute differences between boys and girls
go from one pull-up (ES=0.21) at age 7 to four chin-ups (ES= 1.25) at age 13
to nine chin-ups (ES=2.43) at age 18. Significant adjustments are made using
the linear composite of covariates beginning at 7 years of age and continuing to
18 years of age. The adjustments are nearly to 0 ES for 7- and 8-year-olds.
Sit-ups. Unadjusted values for sit-ups are not significantly different for
boys and girls at 6 or 7 years of age. Differences become significant at 8 years
Table 3
Health Related Physical Fitness Tests
Unadjusted
Age
Test
Mile (112 mile)
Sit-and-reach
Pull-ups (mod.)
Sit-ups
Mile (112 mile)
Sit-and-reach
Pull-ups (mod.)
Sit-ups
Mile
Sitand-reach
Pull-ups (mod.)
Sit-ups
Mile
Sitand-reach
Pull-ups (mod.)
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
Mile
Sit-and-reach
Boys
M
Girls
M
F
.J'
Adjusted
ES
Boys
M
Girls
M
$
F
ES
-g
12
13
14
15
16
17
18
Pull-ups
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
Mile
Sitand-reach
Pull-ups
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
Mile
Sitand-reach
Pull-ups
Sit-ups
Mile
Sit-and-reach
Pull-ups
Sit-ups
38 - Thomas, Nelson, and Church
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Unadjusted
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-1.25- 1 5 0 4 . 1 . , . I . l . , . , . 1
5
7
9
11
13
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19
Age
Figure 1 - Unadjusted effect sizes and adjusted effect sizes (adjusted for linear
composites of covariates) at ages 6 to 18 years for (a) mile (or half-mile) run; (b) sitand-reach; (c) chin-ups (or modified pull-ups); and (d) sit-ups. (cont.)
61
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40 - Thomas, Nelson, and Church
of age and increase steadily until 17 years of age. The absolute differences go
from one sit-up (ES=0.16) at age 8 to six sit-ups (ES=0.64) at age 13 to ten
sit-ups (ES=0.97) at age 17. Significant adjustments are made using the linear
composite of covariates beginning at 8 years of age and continuing through 18
years of age. The adjustments are nearly to 0 ES for 8- and 9-year-olds.
Discussion
Three of the health related physical fitness measures (mile run, chin-ups, and
sit-ups) reflect similar patterns in the development of gender differences. Figure
1 shows that uncorrected effect sues are small when children enter school. The
differences between boys and girls increase gradually during elementary school.
After puberty, performance differences increase faster on tasks involving
strength, power, and size.
Figure 1 also shows gender differences after adjusting for numerous environmental and physical characteristics measured in the NCYFS, Phases I and 11.
Adjustment factors in the mile run, pull-ups, and sit-ups follow the same general
patterns. Prior to puberty, covariates of importance are generally physical-mainly skinfolds but also height and weight. Following puberty, the major
factors that reduce gender differences are skinfolds and the amount of exercise
outside of school time.
As children get older, the influence of activities outside of school is greater.
For example, in the mile run the number of high-intensity activities, particularly
outside of physical education, is related to mile-run performance from ages 9
through 18. In every instance boys report more high-intensity activity. Although
the absolute differences in high-intensity activities stay the same, there is a steady
decrease in the number reported for both sexes after puberty. The same pattern
occurs for chin-ups and sit-ups. These effects are reinforced by other environmental characteristics. Boys report more activities that cause them to sweat and
breathe hard beginning at about 9 or 10 years of age and continuing throughout
adolescence. Sweating and breathing hard on a more regular basis relates to
increased performance on the mile run, chin-ups, and sit-ups.
Other environmental characteristics likely related to amount and intensity
of exercise outside of school time occasionally come into play. In the mile run,
sit-ups, and chin-ups, total amount of outside activity or amount of exercise as
reflected by kilocalories expended often predicted better performance. Whenever
these characteristics were significantly adjusted for gender differences, boys reported more of the characteristics, such that an adjustment reduced the gender
differences.
The physical variable reflected by skinfolds is an important factor in all
three health related fitness tests after puberty. Skinfold differences between boys
and girls become increasingly greater, reflecting the influence of hormonal differences, that is, boys add muscle and girls add fat (3). Thus, unadjusted effect
sizes increase up to and above 1.0 in the mile run and sit-ups and are even larger
(above 2.0) in chin-ups. Physical and environmental adjustments still result in
reduced effect sizes, but the combination of girls having more fat and exercising
less often and less intensely is clearly reflected by the large effect sizes, unadjusted or adjusted.
Gender Differences in Physical Fitness
- 41
Sit-and-reach performance is entirely different from the other three measures. Girls' performances are better at all ages and increasingly so after puberty.
Few of the physical or environmental characteristics measured in the NCYFS
studies related to sit-and-reach performance, and meaningful adjustments in gender differences were never made. Apparently the gender differences are accounted for by factors not measured in this study.
The results suggest there are gender differences regarding the nature of
activities engaged in outside of school. Compared to girls, boys report that they
participate in more high-intensity activities from about age 9 or 10 on. It could
be speculated that some of the factors influencing gender differences may be
attributed to differential encouragement, practice opportunities, and reinforcement patterns of boys and girls in and outside the school setting, as has been
suggested by several authors (4, 7, 9, 17, 18). However, these factors were not
measured in this study. Similarly, it is likely that several physiologic variables
other than size and fat are gender related, such as hemoglobin concentration and
testosterone levels (3), that could help to explain age and gender differences.
Overall, in view of the relatively small percent of variance accounted for in the
analyses, it appears that a number of factors, perhaps both environmental and
physical, account for gender differences in fitness performance that were not
measured in this study.
References
1. American Alliance for Health, Physical Education, Recreation and Dance. AAHPER
Youth Fitness Test Manual. Reston, VA: Author, 1976.
2. American Alliance for Health, Physical Education, Recreation and Dance. AAHPERD Health Related Physical Fitness Test Manual. Reston, VA: Author, 1980.
3. Brooks, G.A., and T.D. Fahey. Exercise Physiology: Human Bioenergetics and its
Applications. New York: Wiey & Sons, 1984.
4. Corbin, C.A. A Textbook of Motor Development. Dubuque, IA: Brown, 1973.
5. Espenschade, A.S., and H.M. Eckert. Motor Development. Columbus, OH: Merrill,
1967.
6. Fohlin, L., C. Davies, U. Freyschuss, B. Bjarke, and C. Thoren. Body dimensions
and exercise performance in anorexia nervosa patients. In: Pediatric Work Physiology, J. Borms and M. Hebbelinck (Eds.). New York: Karger, 1978, pp. 102-107.
7. Greendorfer, S.L. Gender differences in physical activity. Mot. Skills: Theory Into
Practice 4933-90, 1980.
8 . Hall, E.G., and A.M. Lee. Sex differences in motor performance of young children:
Fact or fiction? Sex Roles 10:217-229, 1984.
9. Housner, L.D. Sex-role stereotyping: Implications for teaching elementary physical
education. Mot. Skills: Theory into Practice 5: 107-116, 1981.
10. Hunsicker, P., and C. Reiff. Youth fitness report, 1958-1965-1975. J. Phy. Ed.
Rec. 48(1):31-33, 1977.
11. Johnson, B.L., and J.K. Nelson. Practical Measurementsfor Evaluation in Physical
Education (4th ed.). New York: Macmillan, 1987.
12. Milne, C., V. Seefeldt, and P. Reuschlein. Relationship between grade, sex, race,
and motor performance in young children. Res. Q. 47:726-730, 1976.
13. National Center for Health Statistics. Basic data on anthropometric measurements
42
- Thomas, Nelson, and Church
and angular measurements of the hip and knee joints for selected age groups, 1-74
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Acknowledgment
This secondary analysis of the NCYFS Study I and I1 was prepared under U.S.
Government contract #282-85-0060, Department of Health & Human Services, Public
Health Service.