Body composition and physical fitness of undernourished South ...

European Journal of Clinical Nutrition (2005) 59, 877–883

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ORIGINAL COMMUNICATION Body composition and physical fitness of undernourished South African rural primary school children MA Monyeki1*, LLJ Koppes2, HCG Kemper2, KD Monyeki3, AL Toriola4, AE Pienaar1 and JWR Twisk2,5 1

School for Biokinetics, Recreation and Sport Science, North West University, Potchefstroom Campus, Potchefstroom, South Africa; 2VU University Medical Center, Institute for Research in Extramural Medicine (EMGO), Amsterdam, The Netherlands; 3Chronic Disease of Lifestyle Unit, Medical Research Council, Tygerberg, South Africa; 4Sports and Physical Rehabilitation Science, Tswane University of Technology, Pretoria, South Africa; and 5VU University Medical Center, Department of Clinical Epidemiology and Biostatistics, Amsterdam, The Netherlands

Objective: The purpose of this study was to determine the relationships between the body composition characteristics, body mass index (BMI), sum of skinfolds (SSF), % body fat (%BF), fat-free mass (FFM) and waist-to-hip ratio (WHR), and nine physical fitness items in undernourished rural primary school children in Ellisras, South Africa. Design: A cross-sectional study. Setting: The study consisted of 462 boys and 393 girls who were aged 7–14 y. Measurements: Five body composition measures were assessed: BMI, SSF, %BF, FFM and WHR. Nine physical fitness test items were assessed: standing long jump, bent arm hang, sit-ups, 10 5 m shuttle run, 50 m sprint, 1600 m run, flamingo balance, sit and reach, plate tapping. Results: BMI was highly correlated with FFM (r ¼ 0.7, Po0.001). In line with findings from Western countries, regression coefficients (B) showed that children with higher BMI or SSF performed worse in bent arm hang (girls, B ¼ 0.84, Po0.001, and B ¼ 0.06, P ¼ 0.02, respectively) and in 1600 m run (B ¼ 6.68, Po0.001). BMI was significantly associated with flamingo balance (B ¼ 0.26, P ¼ 0.04). WHR was positively associated with bent arm hang (B ¼ 9.37, P ¼ 0.03), and inversely with sit and reach (B ¼ 7.48, P ¼ 0.01). In contrast, significant relationships were found between BMI and standing long jump (B ¼ 0.74, P ¼ 0.04), sit and reach (B ¼ 0.51, Po0.001), flamingo balance (B ¼ 0.26, P ¼ 0.04) and plate tapping (B ¼ 19, P ¼ 0.01). SSF was significantly associated with sit and reach (B ¼ 0.04, P ¼ 0.03). Significant inverse associations were found between FFM and bent arm hang (girls, B ¼ 0.06, P ¼ 0.05), 1600 m run (girls, B ¼ 2.33, P ¼ 0.003) and 50 m run (boys, B ¼ 0.11, P ¼ 0.006). FFM was significantly associated with standing long jump (boys, B ¼ 0.99, Po0.001; girls, B ¼ 0.73, Po0.001), flamingo balance (B ¼ 0.17, Po0.001), and with sit and reach (boys, B ¼ 0.59, P ¼ 0.03). Conclusion: In the present study in undernourished children, body composition was significantly related to physical fitness, but not always in the expected direction. It is therefore important to note that in this population, BMI should not be interpreted as a measure of fatness/overweight, but rather as an indicator of muscle mass. Sponsorship: Financial support was received from the Vrije Universiteit, Amsterdam, The Netherlands, and the University of the North, Sovenga, South Africa.

European Journal of Clinical Nutrition (2005) 59, 877–883. doi:10.1038/sj.ejcn.1602153 Published online 25 May 2005 Keywords: Ellisras rural children; body composition; physical fitness; anthropometry

*Correspondence: MA Monyeki, School for Biokinetics, Recreation and Sport Science, North West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa. E-mail: [email protected] Guarantors: MA Monyeki, HCG Kemper, LLJ Koppes and JWR Twisk. Contributors: All authors jointly played a critical role in the development and finalisation of the manuscript. HCGK provided

critical inputs in the writing of the paper. JWRT and LLJK played a role in statistical analyses, the interpretation of the results and writing of the paper. ALT and KDM are collaborators of the Ellisras Longitudinal Study and commented on drafts of the paper. AEP commented on drafts of the paper. Received 29 April 2004; revised 8 March 2005; accepted 10 March 2005; published online 25 May 2005

Body composition and physical fitness of undernourished South African children MA Monyeki et al

878

Introduction Body composition is an important indicator of health status in children and adolescents (Norgan, 1990; Immink et al, 1992; Rolland-Cachera, 1995; Hills & Byrne, 1998; Malina et al, 1998; Bunc, 2001; Deurenberg et al, 2003). In the last decades, information about the relationships between body composition and physical fitness in children from developed countries has been published (Malina, 1975, 1994; Beunen et al, 1983; Malina et al, 1995, 1998). These studies revealed that excessive fatness has a negative impact on performance tasks in which the body is projected through space, as in long jump, sprint, and on tasks in which the body must be lifted in space as in bent arm hang. In contrast with developed countries, little is known about the relationship between body composition and physical fitness in children and adolescents of developing countries like South Africa. This relationship is relevant for public health because in developing countries low fatness can be seen as a result of undernutrition (Spurr, 1988; Malina et al, 1991; Parizkova, 1991), and undernutrition likely is an important risk factor for general health outcomes. Previous studies in developing countries assessing the relationship between body composition and physical fitness were done in chronically undernourished adult males (Viteri, 1971; Barac Nieto et al, 1978; Martorell et al, 1992) and children (Malina & Little, 1985; Malina et al, 1998). In contrast with findings in well-nourished populations some of these studies indicated that body composition may have a positive relationship with physical fitness items. A study conducted by Be`ne`fice and Malina (1996) in rural Senegalese children living under chronic undernutrition revealed that the relationships between body composition and physical fitness (run, jump, throw and grip strength) were opposite while those in a study of South African urban children were generally similar to those in well-nourished children (Sloan, 1966; Pienaar et al, 1997). It is not clear whether or not the relationship between body composition and physical fitness of undernourished rural children in South Africa is similar to that in urban South African children or whether it is similar to that in rural Senegalese children. From a public health perspective, improvement of both nutritional status and physical fitness can be seen as an important tool for the improvement of the well-being of children and for the prevention of diseases. Although improvement of nutritional status is the most important, improving physical fitness can play an important additional role. As a result, it is important to investigate the determinants of physical fitness in undernourished children. Therefore, the purpose of this study is to determine the relationship between body composition and physical fitness in undernourished rural children in South Africa.

Subjects and methods Design of the study This study is part of the Ellisras Longitudinal Study (ELS) (Monyeki et al, 2000), which aimed at examining the European Journal of Clinical Nutrition

nutritional status and identifying the growth status of rural school children living in the Ellisras area. The present analyses are based on 462 boys and 393 girls (7–14 y old) who participated in the anthropometric assessments and physical fitness tests in 2001. The nature and scope of the study were explained to the children and their parents who gave informed consent. The Ethics Committee of the University of the North in South Africa approved the study.

Measurement of body composition Three indices of body composition were obtained from the anthropometric measurements that were performed in accordance with the protocol of the International Society for the Advancement of Kinanthropometry (ISAK) (Norton & Olds, 1996). A Martin anthropometer was used to measure height to the nearest 0.1 cm and a Schoenle electronic scale was used to measure weight to the nearest 0.1 kg. Body mass index (BMI) was calculated from weight and height (kg/m2). The sum of four skinfolds (SSF) was calculated using measurements taken at the triceps, biceps, subscapular and suprailiac. A Harpenden (John Bull) skinfold calliper with inter-jaw pressure of 10 g/mm2 was used to measure the thickness of four skinfolds to the nearest 0.2 mm. Circumferences of the waist (at umbilicus height) and hip (at the level of the greatest posterior protuberance of the buttocks that usually corresponds anteriorly to about the level of the symphysis pubis) were measured with a flexible steel tape to the nearest 0.1 cm. Waist-to-hip ratio (WHR) was used as an indicator of body fat distribution. More details regarding the study have been described elsewhere (Monyeki et al, 2000, 2003). Percentage body fat (%BF) was based on the sum of triceps and subscapular skinfolds (STSS) using the Equations (1a) and (1b) below of Slaughter et al (1988), which are internationally accepted for the use in children from different ethnic groups. Fat-free mass (FFM) was obtained by subtracting body fat mass from total body weight. Boysðall agesÞ %BF ¼ 1:21ðSTSSÞ 0:008ðSTSSÞ2 þ 1:7 ð1aÞ Girlsðall agesÞ %BF ¼ 1:33ðSTSSÞ 0:013ðSTSSÞ2 2:5

ð1bÞ

Measurement of physical fitness The physical fitness tests included bent arm hang, standing long jump, sit-ups, sit and reach, 10 5 m shuttle run, plate tapping and flamingo balance from European Test of Physical Fitness (EUROFIT, 1988), and 1600 m run and 50 m sprint from American Alliance for Health, Physical Education, Recreation and Dance (AAHPERD, 1980). The physical fitness tests were classified into five categories: three strength tests: (1) standing long jump (cm): the best out of three trials is recorded; (2) bent arm hang (s): a child has to hang as long as possible with its chin above a bar; (3) sit-ups:

Body composition and physical fitness of undernourished South African children MA Monyeki et al 0.16 (0.35) 2.01 (o0.0001) 2.35 (o0.0001) 0.35 (0.35) 0.000 (0.88)

0.011 (0.004)

0.29 (o0.001) 0.42 (o0.001) 0.56 (0.06)

2.8 (0.001) 0.6 (o0.001) Agecorrected gender difference, Boys minus girls (P-value)

Mean change per y (P-value)

(0.1) (0.6) (0.6) (0.5) (0.4) (0.5) (0.5) (0.5) 0.86 0.86 0.87 0.86 0.86 0.86 0.86 0.88 (8.4) (11.9) (6.6) (10.5) (14.8) (8.8) (7.4) (11.9) 27.6 29.6 26.8 27.4 28.8 25.7 25.1 29.5 (8.9) (6.5) (8.6) (9.4) (10.1) (10.1) (14.9) (4.5) 25.0 24.5 24.6 23.9 27.4 26.9 27.0 20.9 (1.5) (1.2) (1.3) (1.8) (1.7) (1.4) (1.1) (1.7) 13.7 14.0 14.4 14.9 15.2 15.9 15.8 16.2 (1.1) (2.0) (1.3) (1.2) (1.3) (1.6) (1.5) (1.2) 13.5 13.8 13.9 14.2 14.5 15.1 15.2 15.0 36 54 60 70 74 67 21 11 46 58 71 80 69 87 35 16 8 9 10 11 12 13 14

BMI: body mass index; SSF: sum of four skinfolds; WHR: waist-to-hip ratio; %BF: percent body fat; FFM: fat-free mass.

0.002 (0.15)

0.15 (0.12)

3.28 (o0.0001)

(3.4) (3.2) (3.6) (3.6) (4.3) (4.2) (6.6) (2.6) 12.8 13.1 12.9 12.7 14.4 14.0 14.1 11.0 (0.6) (0.5) (0.5) (0.5) (0.5) (0.5) (0.5) (0.5) 0.84 0.85 0.84 0.85 0.84 0.86 0.86 0.87

Boys Girls Boys Girls Boys Girls Girls Boys Age (y)

Boys

0.33 (0.19)

(3.2) (3.0) (2.7) (2.7) (4.3) (4.3) (3.6) (5.6) 17.2 18.9 21.4 24.0 26.3 29.9 31.3 28.8 (2.3) (3.2) (3.6) (3.2) (3.1) (4.2) (5.7) (4.7) 18.0 19.9 21.5 23.4 25.3 28.2 29.8 31.7 (5.5) (6.9) (4.4) (5.2) (8.7) (4.9) (5.2) (8.2) 16.8 17.8 16.7 15.6 17.5 15.4 15.7 18.6

Girls

Boys

FFM (kg) %BF WHR SSF (mm) BMI (kg/m2)

Tables 1 and 2 show the means and standard deviations for the body composition and the physical fitness variables, respectively. Significant gender and age differences were observed for most measures of body composition and for most physical fitness tests. The number of children classified as normalnourished and undernourished are presented in Table 3. Seventy-seven percent of the population was undernourished, while none of the children were classified as overweight. Table 4 shows the differences in physical fitness between normalnourished and undernourished children. The normalnourished children performed significantly better in sit and reach and plate tapping, while the undernourished ones performed significantly better than the

Number

Results

Table 1 Means and standard deviations ( ) of body composition characteristics of the 7–14 y old boys and girls

Statistical analysis Descriptive statistics (means and standard deviations) are provided. Differences between boys and girls (corrected for age) and differences between age groups (corrected for gender) were analysed with linear regression analyses. Correlations between body composition indicators (BMI, SSF, FM, FFM and %BF) were tested in gender stratified analyses, by partial correlation analyses, after adjustment for age. To study the relationship between body composition and physical fitness, linear regression analyses were used, corrected for age and gender. Possible effect modification by gender and age was investigated by adding interaction terms to the linear regression analyses. In the case of a significant gender interaction, stratified analyses were performed. In case of a significant age interaction, it is indicated in the Tables. All analyses were performed with SPSS version 11.

Girls

879 a child has to sit down on the gymnasium mat with back upright, hands behind the neck, knees bent at 901 and feet flat on the mat. Then the child has to lie down on his/her back, shoulders touching the mat and return to the sitting position with the elbows out in front so that they touch his/her knees. The number of correctly performed sit-ups in 30 s is recorded. Three tests measure running capability: (1) shuttle run (s): time taken to complete 10 5 m run; (2) 50 m run (s): time taken to complete a 50 m sprint; (3) 1600 m run (s): endurance run, time taken to run four laps of 400 m, One test measures balance (flamingo balance): standing on one leg on a metal beam for as long as possible and the number of times the child is unable to hold balance in 1 min is recorded. One item measures flexibility (sit and reach (cm)): a child has to push a bar forward with the fingers of both hands together while sitting with legs stretched. Furthermore, plate tapping (s) was used to measure speed of the arm; tap a plate 25 times with one hand interchangeably on the left and right sides of the other hand. The five-day test–retest reliability of the measurements was moderate to high (0.4– 0.8) (Monyeki et al, 2003).

European Journal of Clinical Nutrition


1.11 (0.001) 1.31 (o0.001) 0.54 (o0.001) 0.16 (0.20) 0.37 (0.01)

Boys/girls

Boys/girls

34/26 52/42 56/43 66/52 57/50 61/47 29/19 16/8

12/10 6/12 15/17 14/18 12/24 26/20 6/2 —/3

0.50 (o0.001)

7 8 9 10 11 12 13 14

Normalnoursihed (between 15th and 85th percentile)

0.22 (o0.001) 0.27 (o0.001) 5.1 (0.002) 10.8 (o0.001) 0.39 (o0.001) 0.39 (o0.001) 0.39 (0.06) 0.59 (o0.001) 0.22 (0.22) 1.02 (o0.001) 4.4 (o0.001)

2.13 (o0.001) 0.09 (o0.08) 0.34 (o0.001) 52.2 (o0.001) 0.33 (0.01) 1.60 (0.001) 3.22 (o0.001) 4.7 (o0.001)

Mean change pery (P-value)

Agecorrected gender difference, boys minus girls (Pvalue)

Age (y)

Undernourished (below 15th percentile)

normalnourished in bent arm hang, flamingo balance and 1600 m run. Table 5 shows the age-corrected correlations between all body composition indicators for boys and girls. BMI showed larger correlation coefficients with FFM than with SSF or %BF. Since the correlation coefficients between SSF and %BF are almost one, the relationships with the fitness items are only performed for SSF. Table 6 shows the results of the regression analyses regarding the relationships between the body composition indicators and fitness parameters. BMI and FFM showed significant positive relationships with standing long jump, and in girls significant inverse relationships with bent arm hang. No significant relationships were found with sit-ups. SSF and WHR showed significant although opposing relationships with bent arm hang, but not with standing long jump or sit-ups. For the relationship between WHR and bent arm hang a significant positive interaction with age was observed indicating that the association was stronger in the older children. With respect to the running parameters, BMI showed a positive relationship with 1600 m run in girls. No significant relationships were found for BMI with 10 5 m shuttle run and 50 m run, although the latter inverse relationship was close to significance. The positive interaction with age indicates that the inverse relationship was stronger in younger children. A significant inverse relationship was found between FFM and 1600 m run in girls, while FFM was inversely related to the 50 m run in boys. No significant relationships were observed for SSF and WHR with all three running parameters. BMI and FFM were found to have significant positive relationships with flamingo balance and sit and reach, and a significant inverse relationship with plate tapping. These significant inverse relationships were more pronounced in younger than in older children. SSF showed a significant positive relationship with sit and reach, which was stronger in the older children. A significant inverse relationship was found between WHR and sit and reach. Furthermore, an

36 54 60 70 74 67 21 11 46 58 71 80 69 87 35 16 7 8 9 10 11 12 13 14


Table 3 Number of children by age and gender who are undernourished, normalnourished and overweight on the basis of US reference data percentiles (Frisancho, 1990)a

a

5.9 (o0.001)

0.63 (0.005)

(4.5) (2.9) (3.6) (2.8) (2.4) (2.6) (2.9) (4.1) 24.2 21.2 20.3 19.0 17.3 16.9 17.0 18.1 (4.1) (3.3) (3.6) (3.9) (2.8) (2.9) (2.4) (2.2) 24.8 22.4 20.6 20.3 18.3 17.3 16.7 15.2 (5.1) (3.8) (4.6) (4.6) (5.1) (5.0) (4.2) (6.2) 14.4 16.5 15.6 15.8 16.9 17.8 17.6 19.5 (4.2) (4.8) (5.1) (5.1) (5.1) (4.8) (5.3) (5.2) 14.1 15.5 14.3 14.4 15.7 13.8 12.8 14.1 (5.9) (5.4) (5.6) (8.3) (4.9) (4.8) (4.5) (4.6) 12.0 10.3 10.9 10.5 9.3 10.2 8.9 9.3 (7.8) (5.5) (6.0) (5.1) (5.3) (4.6) (4.8) (5.1) 11.5 11.7 10.3 9.8 9.6 9.3 8.9 8.8 (1.1) (0.9) (0.9) (0.8) (1.1) (0.6) (1.8) (1.6) 10.5 10.1 9.9 9.8 9.4 9.1 9.3 9.0 (1.0) (1.1) (1.0) (0.8) (1.0) (0.9) (1.0) (0.7) 10.5 9.7 9.7 9.3 9.1 8.9 8.6 8.3 (42.8) (60.4) (65.1) (53.0) (50.3) (44.1) (83.1) (89.9) 546 528 522 510 498 510 504 528 (36.5) (32.5) (43.1) (39.6) (41.0) (40.4) (34.4) (56.7) 516 486 474 456 450 450 438 408 (3.1) (1.8) (1.7) (1.9) (1.7) (1.5) (1.3) (1.1) 24.3 23.3 22.6 22.8 22.1 21.9 21.6 21.5 (2.3) (1.8) (1.5) (2.2) (1.9) (1.6) (1.2) (1.2) 24.6 22.8 22.0 22.0 21.8 21.8 21.3 20.7 (6.2) (5.4) (6.5) (6.3) (6.6) (6.4) (7.0) (7.3) 14.8 15.3 16.0 17.0 15.0 16.9 13.8 11.4 (4.2) (6.3) (6.7) (5.8) (6.1) (4.4) (4.7) (6.1) 13.8 15.1 15.2 17.2 18.1 17.5 17.9 19.8 (3.7) (4.7) (7.8) (8.2) (4.9) (5.7) (4.3) (9.9) 2.9 3.8 4.6 5.8 4.6 4.7 4.3 5.3 (19.4) 3.6 (3.7) (14.7) 6.3 (6.6) (14.9) 7.1 (7.2) (14.6) 7.3 (7.5) (17.6) 7.6 (0.8) (15.5) 8.9 (8.4) (14.5) 11.2 (7.9) (16.5) 11.5 (10.1) 113.7 117.2 119.5 124.2 133.4 134.6 142.2 138.0 (14.9) (15.0) (16.2) (15.4) (15.3) (17.5) (14.1) (24.3)

Boys Girls Boys Girls Boys Boys Girls

111.2 117.0 125.6 131.9 137.3 140.9 149.1 151.6

Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Girls

Boys

1600 m run (s) Shuttle run (s) Sit-ups Bent arm hang (s) Standing long jump (cm) Number

Age

Table 2

Means and standard deviations ( ) of physical fitness characteristics of the 7–14 y old boys and girls

50 m sprint (s)

Flamingo balance

Sit and reach (cm)

Plate tapping (s)

880

None of the children were classified as overweight (above 85th percentile).


881 Table 4 Means (m) and standard deviations (s.d.) of physical fitness parameters for normalnourished and undernourished children, and the difference between these groups Normalnourished (n ¼ 197) Physical fitness item Standing long jump (cm) Bent arm hang (s) Sit-ups Shuttle run (s) 1600 m run (s) 50 m run (s) Flamingo balance Sit and reach (cm) Plate tapping (s)

m

s.d.

m

s.d.

P-value

130.67 4.50 14.99 22.47 503.39 9.46 10.81 16.64 18.95

17.64 5.77 6.88 2.15 65.93 1.01 5.45 5.47 3.56

128.53 6.86 15.3 22.42 485.01 9.55 9.98 15.37 19.64

19.47 7.59 7.1 1.9 54.69 1.14 5.36 5.01 4.11

0.17 o0.0001 0.55 0.74 o0.0001 0.31 0.06 0.002 0.03

Table 5 Correlation matrix of the body composition variables for boys (right/top) and girls (left/bottom)a

BMI SSF %BF FFM WHR

BMI

SSF

%BF

FFM

WHR

— 0.32* 0.32* 0.71* 0.49*

0.36* — 0.96* 0.22* 0.37*

0.37* 0.95* — 0.22* 0.37*

0.68* 0.07b 0.05b — 0.23*

0.31* 0.31* 0.32* 0.23* —

a

All correlation coefficients are adjusted for age. Correlations are not statistically significant. *Correlations are statistically significant (Po0.001). BMI: body mass index; SSF: sum of four skinfolds; %BF: percentage body fat; FFM: fat-free mass; WHR: waist-to-hip ratio.

b

inverse relationship was found between FFM and plate tapping, which was stronger in the younger children.

Discussion The results of this study in rural South African primary school children show that some of the relationships between body composition and physical fitness are in line, but that most are in contrast with the results of studies in Western countries and to what has been found in urban South African children (Sloan, 1966; Pienaar et al, 1997). Our findings, Table 6

BMI SSF FFM WHR

Undernourished (n ¼ 658)

however, resemble those from a study in rural Senegalese children (Be`ne`fice & Malina, 1996). In Western countries, it is expected that both BMI and the SSF have inverse relationships with performance tasks in which the body is lifted from the ground (as in long jump and bent arm hang) or moved forward (as in sprint). In the present study such a relationship was found for bent arm hang, where children with a high BMI or SSF were less able to hang for a longer time. This was found for 1600 m run also, where the children with high BMI were the slow runners. In contrast with the expectations, children with a higher BMI were able to jump further and to sprint faster. One reason for these differences may be that in Western countries BMI and SSF are indicators of overnourishment (Viteri, 1971; Barac Nieto et al, 1978; Malina & Little, 1985; Martorell et al, 1992; Malina et al, 1998), while in this South African population, there is no overnourishment. A second reason for the opposite findings between the present study and Western studies may be that BMI is an indicator of fatness in Western countries, whereas in a population like ours, a high BMI may indicate higher muscle mass (Malina & Little, 1985; Malina et al, 1998; Taylor et al, 1998). This is supported by the fact that BMI was highly correlated with FFM and that the relationships between physical fitness and BMI were more or less the same as the relationships between physical fitness and FFM.

Regression coefficients (b) for the relationship between measures of body composition and fitness performance controlled for age and gender Standing long jump (cm)

Bent arm hang (s)

Sit-ups

Shuttle run (s)

1600 m run (s)

50 m run (s)

Flamingo balance

Sit and reach (cm)

Plate tapping (s)

b

b

b

b

b

b

b

b

b

0.26*

0.51*

19*T þ

0.00 0.17**

0.04*T þ B 0.59* G 0.04 7.48*

0.02 0.12*T þ

0.74* 0.01 B 0.99** G 0.73** 8.17

B 0.30 G 0.84** 0.06* B 0.03 G 0.06* 9.37*T þ

0.03

0.03

0.02 0.07

0.01 0.00

2.42

0.45

B 0.90 G 6.68** 0.28 B 0.45 G 2.33** 28.57

0.04

Tþ

0.00 B 0.11** G 0.02 0.42

3.08

1.47

Tþ Denotes a positive interaction with age. **Po0.001; *Po0.05 (Only significant beta’s are indicated). BMI: body mass index (kg/m2); SSF: sum of four skinfolds (mm); FFM: fat-free mass (kg); WHR: waist-to-hip ratio.



882 The undernourishment found in the present study is based on the comparison made with the NHANES I and II reference populations (Frisancho, 1990). Comparable with findings by Norgan (1990), Ferro-Luzzi et al (1992) and Immink et al (1992), 80.3% of the boys and 73.0% of the girls fell below the 15th NHANES percentile for BMI. This could explain the apparently contradictory positive relationship between BMI and 1600 m run with the inverse relationship between BMI and 50 m run. The performance in 50 m run relies more on strength (ie, on a high muscle mass) than 1600 m run in which the performance relies more on lower weight than on muscle strength. These findings were consistent with a study conducted in the Zapotec population (Malina et al, 1998). Significant positive relationships were found for BMI and SSF with flexibility (ie, sit and reach). This is consistent with what was reported in a study by Corbin (1984) and may be explained by growth (as expressed by height in BMI) of the lower extremities and the trunk. Another explanation may be the fact that under-nourishment during growth, as is frequently found in our population, may result in anatomical and functional impairments (Malina & Bouchard, 1991). Furthermore, a strong inverse relationship between WHR and sit and reach was found. This relationship was in the expected direction, and can be accounted for by the fact that a big waist (belly) will make it difficult to bend forward. No similar studies were found to compare the present results with. An expected positive relationship was found between BMI and flamingo balance. The children with a high BMI were less able to hold balance. Although borderline significant, this relationship may indicate that balance is less affected by undernourishment than several other aspects of physical fitness. With regard to plate tapping (speed of the arm), an inverse relationship with BMI was observed. In contrast, in a study by Malina and Bouchard (1991) the opposite was found. Again our unexpected finding can be explained by the interpretation of BMI as not being an indicator of fatness but an indicator of muscle mass. The children with more muscle mass are the ones who reach the higher arm speeds. Although there are several significant relationships observed, the magnitude of most relationships are only moderate. It is therefore expected that besides body composition other factors may play a prominent role in defining the level of physical fitness. One factor that may be important here is that the attainment of good results on physical fitness tests requires a high degree of motivation, a sense of competition and ‘aggressiveness’, which are mostly lacking in these children who come from a rural environment where these attributes are not highly valued (Be`ne`fice, 1992, 1998b). Interindividual variation in maturation also may have affected the results because especially in the case of boys, early maturers tend to be stronger and better in physical fitness tests than late maturers (Malina, 1989). Unfortunately, no reliable data on maturation could be collected within the present study. European Journal of Clinical Nutrition

Compared with available EUROFIT, MOPER and AAHPERD reference data (AAHPERD, 1980; Leyten, 1982; Kemper & Verschuur, 1985; EUROFIT, 1992) and data from other studies in developed countries (Malina & Roche, 1983; Parizkova, 1996), the children in the present study performed poorly as compared with children in those studies. Studies conducted in developing countries such as Mozambique found that undernourished children performed better in physical fitness tests of cardio-respiratory fitness and flexibility, but performed poor in absolute strength, as compared to industrialised references (Prista, 2000). In contrast with this, however, standing long jump in rural Senegalese children (Be`ne`fice, 1998a) was better than that in children from the Czech Republic (Parizkova, 1996). Unfortunately, in these studies no other fitness items were compared. In conclusion, the present results on rural South African children were similar to those reported in rural Senegalese and Mozambican children, but were different from urban South African children and children from Western countries. In the present study in undernourished children, body composition was significantly related to physical fitness, but not always in the expected direction. It is therefore important to note that in this population, BMI should not be interpreted as a measure of fatness/overweight, but rather as an indicator of muscle mass.

Acknowledgements The cooperation of community leaders, school authorities, parents and children in the Ellisras area is greatly appreciated. We thank the field workers for their assistance in the collection of the data. The financial support from the University of the North and Vrije Universiteit are acknowledged. We are thankful to the director of the School for Biokinetic, Recreation and Sport Science, Professor DDJ Malan (North West University) and to Dr H van der Erve (Vrije Universiteit) for their support.

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