30 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 HEIGHT, WEIGHT, BODY FAT, STATIC STRENGTH AND EXPLOSIVE POWER OF GIRLS AGED 10-14 TESTED WITH ”EUROFIT” TEST VI[INA, TE@A, TELESNA MA[^OBA, STATI^NA IN EKSPLOZIVNA MO^ DEKLET MED 10. IN 14. LETOM STAROSTI IZMERJENO Z ”EUROFIT” TESTOM Janusz Maciaszek Wiesł ław Osiń ński Abstract The aim of the study is a multifaceted analysis of the relations- hips between height, weight and body fat with static strength and explosive power, determined in accordance with the Eu- rofit test. The subject sample consisted of 1,574 girls 10 – 14 years of age. Body height, weight, the thickness of five skinfolds, static strength and explosive power were measured. The logarithm of the sum of five skinfolds was computed and accepted as a measure of fatness. The subjects were divided into three groups on the basis of this measure: lean, average and fat. Pearson correlation, partial correlation, linear, non–linear regression, analysis of variances and student’s t-test were used for statisti- cal analysis. Body fat is the only parameter, which significantly affects both static strength and explosive power in every age. Body fat de- termined explosive power (r = -0.33 to r = -0.45) more than static strength (r = 0.17 to r = 0.30). The relations are linear in some age groups and non-linear in others. Curvilinear rela- tionships between body fat and both static strength (14-year- olds) and explosive power (11- and 14-year-olds) were obser- ved. In this instance, the explosive power is determined by body fat to a greater extent (D = 21.3% and 17.4%) than sta- tic strength (D = 6.0%), as indicated by higher values of the coefficient of determination. Analysis of variance showed a high level of significance (p≤0.01) of the differences in all age groups. This means that body fat is a factor, which differentia- tes between levels of static strength and explosive power. The above observations confirm earlier results indicating the need for using multifaceted methods of data analysis to study the relations between somatic parameters and physical fitness. Key words: physical fitness, somatic parameters, girls, Eurofit Izvle~ek Namen {tudije je kompleksna analiza odnosov med telesno vi{ino, te`o, ma{~obo in stati~no ter eksplozivno mo~jo, opre- deljenimi v skladu z Eurofit testom. Vzorec je sestavljalo 1.574 deklet med 10. in 14. letom starosti. Izmerjene so bile telesna vi{ina, te`a, debeline petih ko`nih gub, stati~na in eksplozivna mo~. Mero debelosti predstavlja lo- garitem vsote petih ko`nih gub. Na osnovi te mere so bila de- kleta razdeljena v tri skupine: suhe, povpre~ne in debele. Za analizo podatkov so bile uporabljene korelacijska analiza, par- cialna korelacija, linearne in ne-linearne regresija, analiza va- riance in t-test. Telesna ma{~oba je edini parameter, ki statisti~no zna~ilno vpliva na stati~no in eksplozivno mo~ v vsaki starosti. Telesna ma{~oba je bolje opredeljevala eksplozivno mo~ (r = -0.33 do r = -0.45) kot stati~no mo~ (r = 0,17 do r = 0,30). Odnosi so linearni v nekaterih starostih in ne-linearni v drugih – med te- lesno ma{~obo in stati~no mo~jo pri 14. letnicah ter med te- lesno ma{~obo in eksplozivno mo~jo pri 11. in 14. letnicah. V tem primeru je bila eksplozivna mo~ bolj opredeljena s tele- sno ma{~obo (D = 21.3% in 17.4%) kot stati~na mo~ (D = 6.0%), na kar ka`e vi{ji koeficient determinacije. Analiza va- riance je pokazala visoko statisti~no zna~ilnost (p≤0,01) razlik med skupinami, kar ka`e, da je telesna ma{~oba dejavnik, ki razlikuje ravni razvitosti stati~ne in eksplozivne mo~i. Doblje- ni rezultati ka`ejo na potrebo po uporabi ve~ metod analize podatkov za ugotavljanje odnosov med morfolo{kimi parame- tri in telesno pripravljenostjo. Klju~ne besede: telesna pripravljenost, morfolo{ki parametri, dekleta, Eurofit (Received: 19. 07. 2001 – Accepted: 14. 12. 2001) Contact address Wiesław Osiński University School of Physical Education in Poznań ul. Krolówej Jadwigi 27/39 61-871 Poznań Poland Fax: +48 061 8355211 E-mail: Osinski@awf.poznan.pl 31 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 INTRODUCTION The problem of the effect of somatic features on sta- tic strength and explosive power of humans has been touched upon, among others, in the works of Beu- nen et al. (1983), Osiński (1988), Malina et al. (1995), Oja and Jürimäe (1997). Beunen et al. (1983), while studying Belgian boys, proved a similar, negative ef- fect of body fat on static strength (hand grip) and ex- plosive power (vertical jump). The similarity between the effect of body fat on static strength and explosive power was particularly visible after the elimination of the effect of height and weight. A study of girls carried out by Malina et al. (1995) indicated stronger, nega- tive relations between body fat and explosive power (vertical jump) than between body fat and static strength (hand grip). In the work of Osiński (1996) the values of coefficient of determination for the relation between body fat and explosive power (vertical jump) were three times higher than the respective values for the relation between body fat and static strength (tri- al on the leg-back dynamometer). Oja and Jürimäe (1997), who determined explosive power on the ba- sis of the standing broad jump, noted a significantly higher coefficient of variation in groups of girls than in groups of boys. Malina and Reyes (1994) observed that the differences in static strength and explosive power between the lean body mass and the fat (cal- culated per unit of weight) vary significantly, depen- ding on the age of the subjects. Among studies one can find works in which no signi- ficant relations between static strength and explosive power and height, weight and body fat were found (Raudsepp, & Jürimäe, 1996b). In other works no sig- nificant correlation was found between functional strength, determined on the basis of the time of han- ging on a bar, and body fat (Raudsepp, & Jürimäe, 1996a). A study by Copley (1987) did not prove a re- lation between static strength measured using a dyna- mometer and body weight. Results of other studies indicate significant straight-line relations between ex- plosive power (standing broad jump) and static strength (hand grip) with somatic features (Malina et al., 1995; Benefice, & Malina, 1996; Raudsepp, & Jürimäe, 1998). In the majority of the studies the analyses of relations between body fat and strength are based on straight-line methods. The partial corre- lation method and in particular non-linear regression analysis are seldom applied. Belgian studies indicate that the level of strength does not always change pro- portionally to the increase in body fat (Beunen et al., 1983). It has been proven that these relations are of- ten non-linear (Osiñski, 1996; Bober, 1996; Macias- zek, 1999). Thus, it is difficult to determine clearly the relations between strength and body fat. The aim of the study is a multifaceted analysis of the significance of height, weight and body fat for static strength and explosive power determined in accor- dance with the Eurofit test (1993). METHODS Subjects The sample consisted of girls from primary schools in Poznań 10, 11, 12, 13 and 14 years of age. The age categories were made according to the recommen- dations of Malina and Bouchard (1991) and Eurofit (1993). In total 1,574 girls were studied. Detailed in- formation is presented in Table 1. Procedures Anthropometric measures were taken in a standing, straight position, except the skinfold on the calf, which was measured while sitting. Body height, weight and the thicknesses of five skinfolds (biceps skinfold, tri- ceps skinfold, subscapular skinfold, calf skinfold and suprailiac skinfold) were measured. Then the loga- rithm of the sum of five skinfolds was computed and used as a measure of body fat. The subjects were divided into three groups on the basis of this body fat measure: a) the level of 15 cen- tiles was the top limit for lean individuals, b) the ran- ge from 25 to 75 centiles was used for individuals with medium, c) the level of 85 centiles was the lowest va- lue for the group of the fat. The individuals with body fat 15 - 25 and 75 - 85 centiles were excluded from the analysis. The aim of the exclusion was to obtain groups of distinctly different individuals. The method of division presented, was used earlier in the studies of Garn and Clark (1976) and Chrzanowska (1992, 1993). Hand-grip and standing broad jump (from the Euro- fit test) were used to determine the static strength and explosive power. The relationship between height, weight, body fat, static strength and explosive power was calculated by zero order correlation, partial cor- relation and non-linear regression analysis. Differen- ces between the groups classified as lean, medium and fat were analysed with analysis of variance and post-hoc two-group differences with student’s t-test. Age 10 years11 years12 years13 years 14 yearsTotal Num-ber 255 334 302 326 357 1,574 Table 1. The number of studied girls by age groups 32 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 RESULTS The analysis of the relations between somatic parame- ters and static strength started with determining the value of correlation coefficient (Table 2). The strongest relations are between static strength and height. The correlation coefficients have values from r = 0.36 to r = 0.48. Weight has a similar effect on static strength (from r = 0.35 to r = 0.55). The lowest (statistically significant) values of correlation coefficients were no- ted for the relations between the thickness of skin- folds and static strength (from r = 0.17 to r = 0.30). The cases of relation between somatic parameters and explosive power are also frequent (Table 3). The rela- tions between the height and explosive power are sig- nificant at the ages 10, 11 and 14 years, but the va- lues of correlation coefficients are low (from r = 0.13 to r = 0.15). Weight defines explosive power to a stronger degree but negatively (from r = –0.15 to r = –0.22). The effect of weight on the results of long jump isn’t statistically significant only for 12 year-old girls. The effect of the thickness of fat on the explosi- ve power is the strongest. In every age group the in- crease in body fat results in a decrease in explosive power. The values of the correlation coefficient ran- ge from r = –0.33 to r = –0.45. Table 4 presents the relations between static strength and the thickness of the skinfolds, where the effect of height and weight (individually and simultaneously) has been eliminated. The picture of linear relations between static strength and the thickness of skinfold, presented above, changes when height or weight are partialised. After the elimination of the effect of height the relation between the thickness of fat tissue and static strength, with the exception of 11 year-old girls, is significant, but the values of correlation are lower (from r = 0.13 to r = 0.25). After the elimination of weight, the relation (except in the group of 10 year olds) is negative and ranges from r = –0.17 to r = –0.34 (p≤0.01). Thus, with the same weight, the in- crease in body fat results in a decrease in static strength. Interesting results were obtained when the relations between body fat and static strength were studied, af- ter the elimination of the effects of both height and Variables /Age 10 years11 years12 years13 years14 years Height 0.48** 0.36** 0.47** 0.46** 0.40** Weight 0.44** 0.35** 0.55** 0.48** 0.46** Body fat 0.30** 0.17** 0.24** 0.20** 0.21** Table 2. Correlation between static strength and height, weight, body fat ** - p ≤ 0.01 * - p ≤ 0.05 Variables /Age 10 years11 years12 years13 years14 years Height 0.13* 0.15** 0.12 0.03 0.13** Weight -0.15* -0.18** -0.09 -0.21** -0.22** Body fat -0.45** -0.43** -0.33** -0.40** -0.40** Table 3. Correlation between explosive power and height, weight, body fat ** - p ≤ 0.01 * - p ≤ 0.05 Age 10 years11 years12 years13 years14 years Height constant 0.18** 0.10 0.13* 0.13* 0.25** Weight constant -0.08 -0.17** -0.34** -0.30** -0.23** Both variables constant 0.07 -0.08 -0.30** -0.21** -0.10 Table 4. Second order partial correlation between body fat and static strength ** - p ≤ 0.01 * - p ≤ 0.05 Age 10 years11 years12 years13 years14 years Height constant -0.52** -0.49** -0.39** -0.41** -0.41** Weight constant -0.54** -0.48** -0.43** -0.38** -0.38** Both variables constant -0.46** -0.35** -0.36** -0.34** -0.30** Table 5. Second order partial correlation between body fat and explosive power ** - p ≤ 0.01 * - p ≤ 0.05 33 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 weight. In four age groups the correlation coefficient has a negative value, whereas this value is statistically significant for 12 and 13 year-old girls (r = -0.30 and r = -0.21). Thus, the positive effect of body fat on sta- tic strength, proved on the basis of correlation, is on- ly apparent. Then the relations of explosive power were analysed in a similar way, i.e. using the partial correlation met- hod (Table 5). In each case the relation between body- fat and explosive power was negative (p≤0.01), that is with an increase of thickness of fat tissue the stan- ding broad jump result decreases. The highest values of the partial correlation coefficient were noted after the elimination of weight (from r = -0.38 to r = –0.54), therefore an increase of body fat with the same weight affects the level of explosive power very negatively. The elimination of the effects of weight, height or both variables at the same time, in the study of the relations in question, did not affect significantly the values of correlation coefficients. The values of partial correla- tion coefficients ranged from r = -0.30 to r = –0.54. Another step of the analysis of relations of body fat with static strength and explosive power was determi- ning the regression equations and a graphic presen- tation of this relation. For groups of girls 10 to 13 years old, the significant relations between body fat and sta- tic strength are sufficiently well described by a straight line (Fig. ). The increase in thickness of skinfolds is re- lated to increased static strength. In a group of the ol- dest of the studied girls (14 year-old), in the range of high body fat values, the curve is broken and with a further increase in thickness of skinfolds there is a drop of static strength (D = 6.0%). The value of coef- ficient of determination for the analysed regression equations ranges from D = 2.7% to D = 8.9%. Figure 2 shows regression lines, which present the changes in the explosive power (standing broad jump), depending on the body fat in individual age groups. At the ages of 10, 12 and 13 years the rela- tion is described by straight lines which show a syste- matic decrease of explosive power with an increase in skinfold thickness. Coefficient of determination amounts here to D = 20.5%, D = 11.4% and D = 10 years y=2,203+0,0706*x D=8,9% Log 8 10 12 14 16 18 20 100 135 170 205 240 11 years y=10,058+0,0458*x D=2,7% Log 14 15 16 17 18 19 20 21 22 100 135 170 205 240 12 years y=7,330+0,0790*x D=5,9% Log 14 16 18 20 22 24 26 28 100 135 170 205 240 13 years y=11,934+0,0679*x D=3,8% Log 18 20 22 24 26 28 30 100 135 170 205 240 14 years y=-62,824+0,930*x-0,0023*x^2 D=6,0% Log 4 10 16 22 28 34 100 135 170 205 240 Fig. 1. Regression curves for the relations between static strength measured by hand grip (kg) with the fatness in girls aged 10–14. 34 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 16.3%, respectively. In the groups of 11 and 14 year olds, the curve, which best describes the relations is a parabola (D = 21.3% and D = 17.4%). From this analysis a conclusion can be made that the optimal body fat to be able to perform an effective standing broad jump is average to close to medium. Then the level of static strength and explosive power of girls in groups with different degree of body fat was analysed. The basic statistical description is presen- ted in Table 6. As a result of the analysis of variance it was found that the value of the F test has a high le- vel of relevance (p≤0.01) in all age groups. This means that body fat is a factor, which does differentiate the levels of static strength and explosive power. For static strength, the largest differentiation is noted between lean and fat girls (t-test from 3.4 to 4.6, p≤0.01). Lean and medium girls differ in terms of sta- tic strength at the age of 12, 13 and 14 (t-test from 2.0 to 3.5, p≤0.01 or p≤ 0.05). The smallest differences were noted between medium and fat girls (for 10 and 13 year old, p≤ 0.05). The variation of the level of explosive power, due to the level of body fat is, even greater than in the case of static strength (from F = 11.40 to F = 27.53, p≤0.01). The differences were noted in all the age groups between the fat and lean girls (t-test from 16.5 to 28.7, p≤0.01) and between the fat and medium. Only for girls aged 11 and 14 no differences in the ex- plosive power are noted between lean and medium. The variation of the explosive power between lean and fat girls aged 10, 13 and 14 is 28.7 cm, 28.2 cm and 28.1 cm, respectively, which is over 16%. The graphic picture of the variation expressed in cen- tiles of the level of static strength (Figure 3) and explo- sive power (Figure 4) of girls in different fractions of body fat indicates how well groups of the lean and fat girls are distinguished. Fat girls have better results in static strength than lean or medium girls. The differen- 10 years y=230,246-0,5094*x D=20,5% Log 100 110 120 130 140 150 160 170 180 190 100 135 170 205 240 11 years y=24,764+1,8807*x-0,0066*x^2 D=21,3% Log 90 100 110 120 130 140 150 160 170 100 135 170 205 240 12 years y=223,955-0,3698*x D=16,3% log 130 140 150 160 170 180 190 200 100 135 170 205 240 13 years y=249,870-0,4930*x D=16,3% Log 120 130 140 150 160 170 180 190 200 210 100 135 170 205 240 14 years y=51,358+1,8224*x-0,0066*x^2 D=17,4% Log 100 110 120 130 140 150 160 170 180 190 100 135 170 205 240 Fig. 2. Regression curves for the relations between explosive power measured by standing broad jump (cm) with the fatness in girls aged 10–14. 35 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 Table 6. Level of hang grip (kg) and standing broad jump (cm) in individual groups of body fat with the as- sessment of relevance of differences between lean, medium and fat girls Age Lean (L) Average (A) Fat (F) Value Values of t-test (years) of N χ SD N χ SD N χ SD F test L-A A-F L-F HAND GRIP 10 33 12.6 3.5 102 13.7 4.2 34 16.2 4.1 7.4** 1.1** 2.5** 3.6** 11 34 16.0 4.2 137 17.6 5.6 46 19.6 4.5 4.8** 1.6** 2.0** 3.6** 12 35 17.9 5.5 116 21.4 5.5 37 22.5 4.8 7.1** 3.5** 1.1** 4.6** 13 43 21.8 4.7 125 23.8 5.8 45 26.4 6.3 6.9** 2.0** 2.6** 4.6** 14 38 23.9 5.6 116 27.3 5.5 37 27.3 5.2 5.3** 3.4** 0.0** 3.4** STANDING BROAD JUMP 10 35 154.1 19.1 106 145.2 17.1 38 125.4 27.2 19.2** 8.9** 19.8** 28.7** 11 38 152.2 30.7 149 154.7 16.6 51 135.7 14.8 27.5** 2.5** 19.0** 16.5** 12 35 168.3 16.3 116 162.0 16.5 37 149.2 21.4 11.4** 6.3* * 12.8** 19.1** 13 43 174.8 21.7 125 163.2 17.9 45 146.6 28.6 18.8** 11.6** 16.6** 28.2** 14 38 172.6 16.9 116 168.9 19.9 37 144.5 30.3 19.0** 3.7 ** 24.4** 28.1** ** - p ≤ 0.01 * - p ≤ 0.05 01 0 55 55 31 67 49 36 63 54 30 64 49 36 70 46 36 20 30 40 50 60 70 80 90 100 10 years 11 years 12 years 13 years 14 years Centiles Fat Average Lean 01 02 0 15 56 64 21 72 26 52 65 19 57 52 16 51 69 30 40 50 60 70 80 90 100 10 years 11 years 12 years 13 years 14 years Centiles Fat Average Lean Figure 4. Level of standing broad jump (explosive power) of girls by age groups qualified for different body fat groups Figure 3. Level of hand grip (static strength) of girls by age groups qualified for different body fat groups 36 Maciaszek, J., Osiński, W. (2001). Height, weight, body fat, static strength and explosive power of girls aged… KinSI 7(1–2), 30–37 ces noted, however, are not as large as in the case of variation in explosive power, where the group of fat girls have much lower results than girls from the lean group or from the medium group. DISCUSSION The study, in particular the application of correlation, partial correlation, non-linear regression analysis, and analysis of variance, as well as determining the centi- le level of factors of physical fitness; made it possible to determine relations between the level of static strength and explosive power and height, weight and the thickness of skinfolds. The analyses of relations have shown how big a mi- stake can be made in drawing premature conclusions only on the basis of the correlation coefficient. Cor- relation coefficients indicate that the increase in height, weight and thickness of skinfolds positively af- fects static strength of girls 10 to 14 years of age (p≤0.01). However, the thickness of skinfolds is not the main and direct determinant of the level of static strength. A high level of body fat usually coincides with high total weight, and the weight in turn depends to a large extent on the mass of muscle tissue, which plays a basic part in static strength trials (Raudsepp, & Jürimäe, 1997). Strong positive relations between sta- tic strength and body fat were also observed in other studies (¯ak, 1991; Benefice, & Malina; 1996; Kim, & Tanaka, 1997). However, as a result of our own stu- dies, we found that the „pure« effect of body fat on static strength, after the elimination of height and weight variables, is negative. Thus, in the study of re- lations between the thickness of skinfolds and the le- vel of static strength, elimination of the effect of weight is a significant condition of an adequate analy- sis. Other scholars have also pointed out a similar mechanism (Beunen et al. 1983; Malina et al., 1995). Explosive power is determined by somatic parame- ters even to a larger extent. The strongest parameter with a negative effect (p≤0.01) is the thickness of body fat. Osiński (1996) has indicated the significance of body fat for the level of explosive power. In the study of young people in the city of Kraków it was also found that the strongest relations are those between the amount of body fat and explosive power and that they are always negative (Żak, 1991). In the adopted method of assessment of explosive power, due to the need to move the whole body in space, body fat is on- ly an unnecessary burden (Oja, & Jürimäe, 1997). This study not only confirms the observations made in other works (Osiński, 1988; 1995; 1996; Pate, Slentz, & Katz, 1989), but also extends the knowledge on the linear and non-linear relations shown by the results of the assessment of static strength and explosive power measured in accordance with the instructions of the popular Eurofit test. The relations between the thick- ness of the skinfolds and elements of physical fitness are not always clear, uniform and independent of age. The relations in question are linear in some age groups and non-linear in others. In spite of additional com- plications resulting from the introduction of quadra- tic equations, the precision of matching the regres- sion curve to empirical data is multiplied, thus the reasoning becomes more reliable (Ambro`i~, 1999). As a result of such statistical analyses one can say that low body fat is not always the factor, which facilitates carrying out a physical exercise. Claessens et al. (1998) observed that body fat correlates with the distinguis- hed factors of fitness related to health only in the area of average fitness results. However, body fat does not affect results on the high (>P75) or low (