Gender Differences in Fundamental Movement Patterns, Motor Performances, and Strength Measurements of Prepubertal Children

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1 Pediatric Exercise Science, 1995, 7, O 1995 Human Kinetics Publishers, Inc. Gender Differences in Fundamental Movement Patterns, Motor Performances, and Strength Measurements of Prepubertal Children Lennart Raudsepp and Mati Paasuke The purpose of this investigation was to examine the gender differences in kinematics of running at maximal speed and overhand throwing, motor performances, and muscle strength in prepubertal children. Sixty 8-year-old children (33 boys and 27 girls) participated in this study. There were no sex differences with respect to the running kinematics, but in overhand throwing kinematics, motor performances, and muscle strength the boys surpassed the girls <.05). However, in sit and reach and balance the girls surpassed the boys. Nonsignificant correlations (r = ) were found between the majority of variables. These results indicate gender differences in overhand throwing kinematics, motor performances, and muscle strength in prepubertal children. Gender differences in motor development appear during the whole of the child's development process. Examining these differences is an important question in many practical settings, especially in the fields of physical education and youth sport. It appears that gender differences in motor performance are explained by the interaction of environmental and biological factors (7, 17, 29). Previous studies have demonstrated that body composition is a factor that affects the performance of various measures of physical fitness and motor performance (16, 31). Numerous research studies involving prepubertal children have found body fatness to be inversely related with different motor performance tasks (15, 26). In general, if biological variables (age, height, weight, body fatness) were used in predicting motor performance, an average of only 30% of the performance variance would be explained. This finding emphasizes the plausibility of other factors contributing to the motor performance in prepubertal children (15). The developmental curves of the majority of motor performance tasks have relatively similar trends. Across the preschool and elementary school years, small gender differences appeared in motor performance in favor of boys. During puberty and throughout adolescence, gender differences increase (3,6,8). Moms et al. (22) have reported that age was generally related more to motor performance than to gender. Developmental aspects and gender differences of fundamental movement patterns are usually examined on the basis of movement kinematics (4, 10, 13, Lennart Raudsepp and Mati Pisuke are with the University of Tartu, 18. ~likooli Street Tartu EE 2400 Estonia.

2 Gender Differences , 21, 24, 28). Running and overhand throwing developmental %patternshow certain differences. The kinematics of running resembles the adult running pattern already by the age of 5-6 years (4, 8, 21). Research results have revealed that gender differences in running kinematics were associated with the movement of the swing leg (10). Gender differences in overhand throwing kinematics appear already in early preschool years, and these differences are both qualitative and quantitative. Halverson et al. (13) reported that boys not only participated more in organized throwing activities than girls but also remembered practicing overhand throwing more frequently than girls. The majority of motor development studies have reported separately gender differences in motor performance variables and fundamental movement patterns. The purpose of this study is to examine the gender differences in both fundamental movement patterns, motor performances, and strength measurements in the same prepubertal children. Subjects Methods The subjects were 60 healthy 8-year-old elementary-school children of whom 33 were boys and 27 were girls. Children and their parents were informed about the nature of this study, and written consent from each child's parents was obtained. Kinematic Characteristics Two testing sessions were required to complete testing of the given subjects in running and overhand throwing. In the first session the kinematics of running at maximal speed was recorded. The distance of running was 20 m. During data recording each child was first videotaped while standing on the running course holding a meter stick that served as a linear scale. In order to locate joint centers, markings were placed on the joint centers of the limbs. Three trials of each child were recorded with the help of a Panasonic videocamera located to the left of the child. The camera objective was placed perpendicular with the running course. The distance between the camera and the child was 20 m. In a second session the kinematics of overhand throwing was recorded. From a standing position each child performed three trials with a tennis ball (weight 150 g). The child's task was to throw as far as possible. Two-dimensional videotape analysis was employed to obtain the kinematic characteristics. The videotape data were processed by a computer program that provided frame-byframe stick figure computer graphics. The 40 ms frame-by-frame interval was used in data analysis. Motor Performances Characteristics All children participated in two introductory classes during a 3-day period prior to the evaluation of motor performances and muscular strength. During this time the children were taught the proper technique of each exercise. In addition, an

3 296 - Raudsepp and Paasuke instructor explained the motor performance and muscular strength tests, which the children practiced. Five tests were used from the EUROFTT test battery (9): standing long jump, 10 x 5 m shuttle run, sit and reach, Flamingo balance test, and plate tapping. Additionally, 30-m sprint running was used to evaluate the maximal running speed. The results were recorded with a stopwatch at the accuracy of 1.0 s. A seated two-hand medicine ball (weight 1 kg) pushing test was used to evaluate upper body motor performance. Each child was asked to sit on the floor with both feet stretched forward on the floor. The child held the medicine ball against the chest and under the chin, then pushed the ball upward and outward to the maximum distance. There were three trials and the furthest distance from the chest perpendicular to the floor, to the point of ball contact with the floor was recorded. The results were recorded with a metal tape measure at the accuracy of 1 cm. Maximal Muscular Strength In laboratory conditions the maximal muscular strength of various muscle groups was recorded. A 10-min warm-up period was used. All children were rested and motivated to produce maximal effort. The maximal muscular strength characteristics were recorded in the isometric muscular work regimen with the help of dynamometric chairs. Twenty-one randomly selected boys and girls participated in a pilot study to evaluate the reliability of muscular strength tests. The second testing session was carried out 5 days after the initial tests. Significant test-retest correlations (r = in boys and r = in girls) were found. Maximal isometric two-leg extension strength (referred to as total legs strength) was recorded with the knee angle of 110" and hip angle of 120" on a leg dynamometric chair. The subjects were told to produce on command maximum force against the force platform placed under their feet. Maximal isometric knee extension strength was recorded with the knee and hip angles equal to 90" and 1 lo0, respectively. An experimental knee extensors dynamometric chair was used. The force produced by isometric voluntary contractions of the right knee extensor muscles was recorded with a strain gauge. An elastic strap was placed around the distal part of the ankle above the malleoli and connected to the strain. Maximal isometric ankle plantarflexion strength was recorded using ankle plantarflexion dynamometric chair, where the subject sat with the right leg mounted inside a metal frame and the foot strapped to an aluminum plate. The knees were kept at a right angle, while the ankle joint was dorsiflexed by 20". Maximal strength of plantarflexor muscles was recorded during maximum isometric voluntary contraction by pushing the foot plate. Maximal isometric strength of back muscles was recorded using the back dynamometer. The subjects stood on the platform with the knees fully extended and the head and trunk erect. The handbar was grasped using a pronated (right hand) grip and supinated (left hand) grip. The handbar was positioned across the thighs and, without leaning backward, the subjects pulled it straight upward using the back muscles.

4 Gender Differences Statistical Analysis Means and standard deviations were calculated for all recorded characteristics. The statistical significance of the differences between mean values was tested by Student's t test for unpaired values. Pearson product-moment correlations were used to determine the relationships between recorded variables. Forward stepwise multiple regression analysis was performed with the anthropometric variables as the independent variables for selected kinematic, motor performances, and strength measurements. Statistical significance was set at p <.05. Results The means and standard deviations of body height, body weight, and body mass index (BMI) of boys and girls are presented in Table 1. There are no significant differences between boys and girls in height, and BMI, but boys were significantly heavier than girls. Table 2 summarizes the kinematic parameters of running. Although boys surpassed girls significantly in running speed, there were no significant differences Table 1 Anthropometric Parameters Parameter M SD M SD Height (cm) Weight (kg) * BMI (kgm2) Note. BMI = body mass index. *p <.05. Table 2 Kinematic Parameters of Running Parameter M SD M SD Running speed (mls) * Stride length (cm) Support phase time (s) Air phase time (s) Loss of horizontal speed (rn/s)

5 298.- Raudsepp and Paasuke Table 3 Kinematic Parameters of Overhand Throwing Parameters M SD M SD Throwing result (m) * Horizontal ball velocity (mls) " Angle of ball release (degrees) " Throwing time (s) OO * Swing phase time (s) h Throwing phase time (s) " Table 4 Motor Performance Parameters Parameter M - SD 30 m running (s) * Standing long jump (cm) * Two-hand ball pushing (cm) " 10 x 5 m shuttle run (s) Plate tapping (s) * Sit and reach (cm) * Balance (x) " regarding stride length, duration of support and air phases, and loss of horizontal velocity during the support phase. The kinematic parameters of overhand throwing are presented in Table 3. The distance thrown and all other recorded parameters are significantly different between genders in favor of boys. Table 4 displays the mean motor performance parameters. The boys surpassed the girls significantly in 30-m running, plate tapping, two-hand pushing of ball, and standing long jump parameters. However, sit-and-reach flow and balance resulted in significant differences in favor of girls. There was no significant difference in 10 x 5 m shuttle run results. The maximum muscular strength parameters are presented in Table 5. The maximal muscular strength in all measurements is considerably higher in boys than in girls. Correlations between anthropometric and selected kinematic, motor performances and muscular strength variables are presented in Table 6. Body height

6 Gender Differences Table 5 Maximal Muscular Strength Parameters Parameter (kg) M SD M SD Two-leg extension * Knee extension * Ankle plantarflexion * Back muscles * Table 6 Correlation Coefficients Between Anthropometric and Selected Kinematic, Motor Performances, and Muscular Strength Parameters Parameter Height Weight BMI Height Weight BMI 30 m running (s) Standing long jump (cm) Two-hand ball pushing (cm) Balance (x) Plate tapping (s) 10 x 5 m shuttle run (s) Sit and reach (cm) Two-leg extension (kg) Knee extension (kg) Stride length (cm) Throwing result (m) Note. BMI = body mass index. *p <.05. was significantly associated with standing long jump, two-hand ball pushing, knee extension, and running stride length in boys, and with balance and stride length in girls. Body weight correlated significantly with two-hand ball pushing in boys and with knee extension in both boys and girls. Body mass index was significantly associated with 10 x 5 m shuttle run in both boys and girls and with balance and stride length in girls. Forward stepwise multiple regression analysis (Table 7) revealed that in boys the anthropometric parameters accounted for the largest amount of variance in knee extension strength (60%) and in two-hand ball pushing (53%), whereas in girls variance in balance (52%) and in stride length (41%) was accounted for

7 300 - Raudsepp and Paasuke Table 7 Forward Stepwise Multiple Regression Analysis Summary Parameter R2 F P R2 F P 30 m running (s) Standing long jump (cm) Two-hand ball pushing (cm) Balance (x) Plate tapping (s) 10 x 5 m shuttle run (s) Sit and reach (cm) Two-leg extension (kg) Knee extension (kg) Stride length (cm) Throwing result (m) R2 = coefficient of determination. by the anthropometric variables. For the most of the test results in both boys and girls, 10-30% variance was accounted for by anthropometric parameters. Discussion The results of this study provide evidence for gender differences in overhand throwing kinematics, motor performance, and maximal muscular strength in prepubertal children. Regarding the running kinematic pattern, gender differences were not found. As in many previous studies, the significant advantage of boys in overhand throwing kinematics (13, 28), as well as in the majority of motor performance parameters (8, 12,19,20) and maximal muscular strength (I I), was confirmed. The literature on motor development implies that children have mastered the fundamental movement patterns by the age of 5 or 6 years (6, 8). When examining the maximal speed running kinematic parameters in 8-year-old boys and girls, it became evident that the general characteristics of running did not differ. This finding has not been supported by previous studies (4, 20) because boys and girls have been studied separately. Only Fortney (10) has examined the gender differences in maximal speed running kinematics in 2- to 6-year-old children, and the results revealed that gender differences in parameters were associated with the movement of the swing leg. The results of the current study do not support these findings because the movement of different body segments was not studied. The greater running speed of the boys in the present study is in agreement with Cratty (3, who suggested that boys tend to run about 0.1 m/s to 0.3 m/s faster than the same-aged girls. Regarding the kinematics of overhand throwing, it became evident that clear gender differences appeared between 8-year-old boys and girls. These results

8 Gender Differences support the findings of earlier studies (13, 23, 28) that found similar gender differences in overhand throwing. The throwing distance and horizontal ball velocity are the two more frequently studied kinematic parameters of overhand throwing. In the present investigation boys surpassed girls in horizontal ball velocity by 3 m/s. These data supported other studies (13,28) that examined sex differences in ball velocities. The throwing distance differences found in the present study are closely related with the horizontal ball velocity differences and with other kinematic parameters. One common explanation for developmental differences between sexes is that girls do not have the same amount of experience in overhand throwing as boys (13). The studies examining the motor performance parameters or motor fitness (18) in children have been conducted either in longitudinal or in cross-sectional perspective more frequently on adolescents (2) and do not include the preadolescent years, with the exception of Branta et al. (3) and Haubenstricker et al. (14). From the results of the present study, it appeared that 8-year-old boys significantly surpass same-aged girls in movement speed and lower body explosive strength variables. These findings are not surprising because most motor development studies (3, 6, 22) have reported that gender differences in speed, strength, and explosive strength appeared in preschool years. It is also not surprising that girls surpass boys in balance and flexibility tasks. It seems that in these motor performance tasks, girls surpass boys in most age groups (6, 14). For example, Cratty (5) reported that sex differences in favor of girls in static balance appeared already in 2- to 3-year-old children. The studies examining muscular strength of prepubertal children (1 1, 27) have primarily focused on the trainability of a given ability. The general finding in the present study concerning muscular strength results is that 8-year-old boys significantly surpass same-aged girls. These data are not fully comparable with other studies (1 1) because different muscular work regimens were used. In regard to the correlation analysis, our results demonstrate that in general only low to moderate zero-order correlations were found between the variables. These results reflect an agreement with theoretical expectations and previous research (15, 31). Our results demonstrate that only few significant connections between biological variables and movement kinematics were found. Only stride length of running was significantly associated with body height in both boys and girls (r =.53 and r =.66, respectively). Silva et al. (30) reported that neither height nor weight was found to be related to fundamental motor skills among seven-year-old children. It might be that among preschool and elementary school children, factors other than biological count for gender differences found in motor skills (25). In our study, low or moderate correlations (r =.20-.SO) were found between the majority of motor performances and anthropometric measures. These findings are consistent with the results of previous studies (8, 28, 31). Our study also indicated that the body mass index, as an option to the skinfold measures (I), was significantly associated only with shuttle run in both boys and girls. The magnitude of the relationship between body mass index and other motor performances and maximal muscular strength variables was quite low. As expected, the higher body mass index was found to be associated with poorer performances, especially in the tests requiring movement of the body weight (30-m running,

9 302 - Raudsepp and Paasuke shuttle run, standing long jump). These findings are consistent with those in younger children and youth (15, 16). In order to consider anthropometric measurements differences between sexes as an acceptable explanation for gender differences in movement kinematics, motor performances, and maximal muscular strength variance, stepwise multiple regression analysis was used. Considering that all three anthropometric measurements predicting movement kinematics, motor performances, and muscular strength in children, an average of only 30% of the variance would be explained. Using a similar experimental approach on a study of 7- to 12-yearold boys and girls, a coefficient of determination ranging from 2M5% was found (15, 31). Therefore, these results reflect the plausibility of other factors contributing to the movement kinematics and motor performances of prepubertal children. In regard to sex differences revealed from regression analysis results, boys had higher coefficients of determination that predicted knee extension strength (60%) and medicine ball pushing (53%). For girls, coefficients of determination that predicted muscular strength variance were lower (2628%). These findings indicate that the significant gender differences in maximal muscular strength may be partly explained by the differences of biological variables. In summary, the results of this study indicate gender differences in overhand throwing kinematics, motor performances, and maximal muscular strength variables. In these characteristics 8-year-old boys significantly surpass same-aged girls, except in flexibility and balance tasks. Gender differences were not found in running kinematics. Furthermore, only low to moderate correlations were found between movement kinematics, motor performances, muscle strength, and anthropometric characteristics in both boys and girls. Lastly, sex differences in anthropometric measures are not an acceptable explanation for the differences in overhand throwing kinematics, motor performances, and muscle strength in prepubertal children. References 1. American Alliance for Health, Physical Education, Recreation and Dance. The AAHPERD Physical Test Program. Reston, VA: Author, Beunen, G.P., R.M. Malina, M.A. Van't Hof, J. Simons, M. Ostyn, R. Renson, and D. Van Gemen. Adolescent Growth and Motor Performance: A Longitudinal Study of Belgian. Champaign, IL: Human Kinetics, Branta, C., J. Haubenstricker, and V. Seefeldt. Age changes in motor skill during childhood and adolescence. Exerc. Sport Sci. Rev. 12: , Brown, E.W. Biomechanical Analysis of the Running Patterns of Three to Ten Years of Age. Unpublished doctoral dissertation, University of Oregon, Cratty, B.J. Perceptual and Motor Development in Infants and Children. New York: Macmillan, DeOreo, K., and J. Keogh. Performance in fundamental motor tasks. In: A Textbook of Motor Development, C.B. Corbin (Ed.). Dubuque, IA: Brown, 1980, pp Eaton, W.O. Childhood sex differences in motor performance and activity level: Findings and implications. In: Normalities and Abnormalities in Human Movement, B. Kirkcaldy (Ed.). Basel, Switzerland: Karger, 1989, pp

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