META-ANALYSIS OF QUANTITATIVE DIFFERENCES OF ANTHROPOMETRIC CHARACTERISTICS AND MOTOR ABILITIES OF CHILDREN AGED 6 AND 7 YEARS

Meta-analysis carried out for the purposes of investigating motor abilities and morphological characteristics showed diff erences between boys and girls ages 6 and 7 years old. Th e analyses were carried out for 5 anthropometric and 7 motor variables, and the sample taken for analysis was 1000 respondents for each variable respectively. Th e results showed that boys were taller and heavier and the girls had more body fat. Th e investigation of motor skills showed that boys are better at the variables used to assess coordination in young children (Obstacle course backwards, 20-m dash and Standing long jump), while girls achieved better results in the variable which is used for estimating fl exibility (Standing bend forward). In other motor variables there were signifi cant diff erences between boys and girls, which confi rms the results of previous studies of the quantitative gender-related diff erences and points to possible solutions for an improvement of coordination in girls and fl exibility in boys.


INTRODUCTION
Organized physical activities for children start from the earliest period in pre-school institutions.Working with children in kindergarten is conducted by A or B model of Rulebook on basic principles of preschool program (2006), and physical activities are conducted by implementing diff erent forms of work.Positive eff ect on the children can be seen through the proper growth and development of intellectual, emotional and motor skills, acceptance of certain norms of behavior, desirable habits, etc.
Th e planning and programming of physical activity of children are aff ected by various factors, some of which are: age, frequency of body activities practicing, living conditions, the size and equipment of the space where the practice is performed, the scheduled time for exercise, place of residence, etc. Physical ac-Previous studies have shown that the biological growth and development of boys and girls is very similar in the preschool age (Bala, 1981;Bala, Jakšić, & Popović, 2009), but still there are some diff erences.In the morphological space, the most pronounced diff erence between boys and girls, 6 and 7 years old, appears in the variables used to evaluate the body height, body weight, forearm girth and chest girth (Bala, et al., 2009).Th e same research also identifi ed in the fi eld of motor abilities pronounced diff erences in older children, and that is precisely one of the reasons why the age of 6 to 7 years (± 6 months), as the oldest in kindergarten, was chosen.Statistically signifi cant diff erence in favor of boys appears in the variable used for estimating the coordination of the whole body (Obstacle course backwards) and in variables used for estimating the explosive power of the lower extremities and running speed in adults (Standing long jump and 20-m dash), which are used for coordination assessment in preschool children.On the other hand, girls showed better results in the variable used for estimating the fl exibility (Forward bend).
Another signifi cant reason why this age was chosen is that the parents are obligated to enroll their children in preschool institutions before starting school.Statutory obligation leads to the conclusion that children of that age are mostly in kindergartens, so one of the aims is to determine whether you need to make special programs in relation to gender.
Physical activity in various forms is included in daily and weekly kindergarten schedule, but in some cases there are diffi culties in its implementation (e.g.lack of exterior and interior space, devices, equipment, etc..).Development of motor skills can take place through spontaneous physical activity, but it is more eff ective to develop it through an organized physical activity within an institution (O'Neill et al., 2013; Logan, Robinson, Wilson, & Lucas, 2012) or through sport adequate for an age (Vandorpe, et al., 2012).

METHOD
Meta analysis is a quantitative process, which involves pooling and analysis of data from independent studies about the same problem of research in order to draw conclusions (Bruce, 1996).Th e process of research and selection of variables and calculation of the data is described in detail below.

Selection of studies
Studies in which the authors dealt with anthropometric characteristics and motor abilities of children aged 6 and 7 years (±6 months) were considered for this study.Th e oldest research dating is from 1981 when the motor development of children of that age started being followed in our country.Although the morphological space of preschool children was being explored long before the motor, for this study we didn't accept studies before the reference year.All used research was conducted on the territory of the Republic of Serbia.
Diff erent bibliographic sources were used for data collection: dissertations, monographs, collections of papers and articles published in scientifi c journals.In total 29 published papers were examined, and this study included 11 documents.
A large number of papers where the author dealt with the structure of motor and morphological areas were excluded from the study, because the authors did not identify the basic descriptive characteristics of variables used.Th e authors have studied various problems, such as: the connection of motor and morphological variables (Bala, et al., 2009); connections of motor or morphological variables with cognitive abilities, certain patterns of behavior and some social factors (Bala, & Katić, 2009 Sabo, 2003).All papers dealing with these problems have been used, if the shown tables of the basic descriptive characteristics were separately for boys and girls.Papers in which the authors dealt with the application of some treatment were taken into account, but only the results from the initial measurement were used.In a research conducted by Sabo (2003) children were divided by gender and by years of attending kindergarten in the three groups.Th is study determined the arithmetic mean for these diffi cult to comply with in the morphological space, because the authors worked by the recommendation of the International Biological Program.
Motor behavior of preschool children was examined by applying diff erent tests.All used papers had at least seven motor tests that are commonly used for pre-school children.Minor diff erences in research appear in the application of the Forward bend test and Sit-ups for 60-s, which is about to be discussed.Table 1 shows the aggregate information from applied research for each variable.three groups, and this result was added to the results from other studies for each gender separately.

Th e choice of variables
Th e application of diff erent measuring instruments in research causes the rejection of certain variables for this study.Care has been taken so to use the same measuring instrument in all surveys for assessing certain variables.Th is criterion was not During data collection, it was observed that there's more papers on morphological characteristics than motor skills, as can be seen from the presented in Table 1.As already mentioned morphological characteristics are studied signifi cantly longer than the motor behavior of preschool children.In addition, morphological space was studied by much more researchers, and in addition to doctors there are also and physical education teachers, and also should not be left out that motor testing is much more complex to implement (implemented during more than 1 day), which leads to loss of respondents during treatment or measurement.

Calculating the eff ect size
Calculating the eff ect size for each variable was performed according to the formula for two independent groups (Cohen, 1988).
m A -the arithmetic mean of variable for boys; m B -the arithmetic mean of variable for girls; σ -standard deviation in the population.
Given that there is a diff erence between the standard deviations of groups of respondents, we used the standard deviation in the population (Cohen, 1988).Th is value is calculated as: σ A -standard deviation of the variable for boys; σ B -standard deviation of the variable for girls.

RESULTS
Th e obtained values for the size of the eff ect, the mean and standard deviation for each variable are shown in Table 2. Also shown are the minimum and maximum values of the variables for a more detailed interpretation.Th e obtained values for the size of the eff ect can be classifi ed into three categories: small diff erences up to 0.20, mid diff erence up to 0.50 and a big diff erence up to 0.80.Such categorization must be considered carefully because it refers to a broad array of social sciences (Cohen, 1988, Valentine & Cooper, 2003), particularly in the research which determine the progress of some group of respondents aft er certain treatment, so the eff ect size of 0.1 can be signifi cant.Legend: M-mean; SD -standard deviation; Min -minimum value; Max -maximum value; d -eff ect size.
Growth and development of preschool children are very dynamic, so a big diff erence between the children can occur even in 6 months.Th e diff erence of the minimum and maximum values is somewhat expected because for this study the data were collected from several diff erent studies, and the children were 6 and 7 years old (± 6 months).
Motor behavior of children, measured by the variables shown, mostly depends on the age, and it is believed that motor development is faster than morphologically, especially if children regularly perform physical activity (Bala, et al., 2009).Here we should point to another phenomenon, which refers to tests conducted.For this study we took into account the variables that were formed on the basis of the results from the same tests.An exception was made for the tests used to evaluate repetitive strength of the torso and fl exibility.In fi ve studies conducted, the fl exibility assessment was performed by seated forward bend and in two other studies (Bala, 1981;Sabo, 2003) by deep forward bend on the bench.Means taken from these studies showed no signifi cant diff erences compared to the values of the remaining fi ve studies.Repetitive strength of the torso was estimated by variable Sit-ups for 60-s.In fi ve studies data were collected using a test where the children put their hands on chest and touched the opposite shoulders, and in one study (Sabo, 2003) kids were placing a bat on their napes.Th e minimum value in this research for the variable Sit-ups for 60-s was in the survey which used a bat.It is assumed that the inappropriateness of the test according to the age was the reason for the lowest average result in this study, so certain tests should be modifi ed according to the age as suggested by Bala, Stojanović and Stojanović (2007).
We notice that the result for the eff ect size in certain variables have a negative sign.Th is phenomenon means that the results were higher in girls than in boys group.Common for all three variables that assess subcutaneous fatty tissue is that the values are higher for girls.Variables used to evaluate running speed (20-m dash) and coordination (Obstacle course backwards) also have a negative sign, but that means that boys performed better, and that they crossed the given distance faster.Th ese two variables in addition to the above skills in young children also evaluate coordination (Bala, et al., 2009).
If we take into account the three categories listed above, the variables: Arm plate tapping and Sit-ups for 60-s can be put into the fi rst category, and there is little diff erence between the groups of respondents in these variables.Th e second category includes variables: Body height, Body weight, Abdominal skinfold, Subscapular skinfold and Bent-arm hang, while the other variables fall into the third category, because for these the biggest diff erence was found between the respondent groups formed according to gender.

DISCUSSION
Skinfolds, which are considered in this study provide information on the subcutaneous fatty tissue, and the results indicate that girls have slightly higher values than boys.Th is result was obtained in all surveys that were taken into account, in which the authors dealt with the diff erences in subcutaneous fatty tissue in boys and girls.To this must be added the other two anthropometric variables, which show that the boys are a little taller and heavier than girls.Dimensionality and voluminosity factors and subcutaneous fat factor are mostly under infl uence of genetic predisposition and environmental factors, especially diet, the volume and intensity of physical activity.One must not forget the fact that boys at birth, on average, are slightly longer, wider and heavier, which probably refl ects the future growth and development, and bigger diff erence considering gender (Sabo, 2003).
When it comes to motor behavior in young children it was observed that almost all potential motor skills are interrelated, so we oft en speak about general motor factor (Bala, 1981) or a twodimensional model where the fi rst factor practically acts as a general, while the other factor, the fl exibility, stays aside (Bala, & Popović, 2007).Th e existence of a general motor factor leads to the conclusion that in the execution of movements in preschool children the whole body participates.
Th e analysis results show that there is a certain diff erence in the motor behavior of boys and girls.Th is is primarily related to the variables used for evaluating the coordination, which are: 20-m dash, Obstacle course backwards and Standing long jump.Th ese tests are used for evaluating completely diff erent motor skills in adults, but in small children are used to evaluate coordination (Bala, et al., 2009).Performing these tests for preschool children is very insecure and is a complex process that requires refl ection and organization of movements and motion.Th is claim is confi rmed by examining the diff erence between children and adults in tests which include jumps, and authors among others conclude that children have worse jumping technique (Harrison, & Gaff ney, 2001).
Result for the size of the eff ect in variable which is used for estimating fl exibility (Forward bendhyperextension) shows that girls are signifi cantly better than boys.Th ese fi ndings suggest that physical activity levels of boys and girls during the day diff er in intensity and scope, which has an impact on some morphological characteristics, but also in the content, so it directly aff ects the motor behavior.Boys practice games where there is more running and jumping as opposed to girls.
Very little diff erence between boys and girls appear in variables used for evaluating the speed of alternative movements (Arm plate tapping), repetitive strength of the torso (Sit-ups for 60-s) and the static strength of the arms and shoulders (Bent-arm hang).Th is could support the general conclusion that physical activity in kindergarten and school sport can be performed by the same program for boys and girls, respectively, and the obtained diff erences are not big enough to conduct separate programs of physical activity for boys and girls.Th is greatly facilitates the work of teachers and trainers in the preparation and implementation of physical activity.
Th is research does not include the analysis of balance skills, and the main reason for that is that the authors opt for diff erent tests or do not deal with the aforementioned motor skills at all.Balance is a motor skill important for maintaining adequate posture and movement, and in some studies with small children it was confi rmed that boys perform better during tests (Mickle, Munro, & Steele, 2011).
Yet in this study, but also in other studies in which authors deal with examining the quantitative diff erences of motor behavior in boys and girls, we came to the same conclusion that boys have better coordination, and that girls are more fl exible.If we want to develop coordination among girls and fl exibility in boys, it could be carried out in groups formed according to gender.Certainly, this separation should not be made during the entire activities but only in the last part.Conducting exercises to develop coordination and fl exibility does not require high energy consumption, so the goals and objectives of the fi nal part of the activities can be bet.Another way is to draw the attention of parents and provide advices so skills could be developed through various exercises inside the family.

CONCLUSION
Tracking morphological and motor space and comparison of boys and girls must be carried out regularly because there is a noticeable diff erence between children of the same age during two diff erent periods.Today's children are taller and heavier and their motor skills are signifi cantly worse ( Runhaar et al., 2010) .Th is phenomenon is probably caused by the change in diet, daily content activities, system of values etc.Also, obese children have poorer motor skills than children of normal weight (Lopes, Stodden, Bianchi, Maia, & Rodrigues, 2012) which is probably due to a smaller or larger scale and intensity of physical activities.
Meta analysis of prospective studies of motor abilities and morphological characteristics of children should be directed to check these results on a larger sample of subjects obtained from a number of research papers.Research should be extended to the study of the diff erences between boys and girls in the structure of motor and morphological space to determine whether diff erent authors come to similar conclusions.For the development of science and practice a research could be conducted to determine if there is a development of fl exibility and coordination if separate exercises are being used for boys and girls in the fi nal part of the activity.

Table 1 .
Basic data of the sample variables

Table 2 .
Indicators of basic descriptive characteristics and eff ects size