Abstracts
OBJECTIVE:
To assess the association between malalignment of the knees (genu valgum) and variables of physical fitness among schoolchildren.
METHODS:
We analyzed data collected between the years 2000 to 2009. The sample comprised 1,141 schoolchildren of both sexes aged 06 to 18 years. To participate in the research, the students must meet the following criteria: age between 6 and 18 years and a full assessment of physical fitness, including measurement of genu valgus in at least one of the semester assessments. Postural evaluation (valgus) was determined by the intermalleolar distance, in centimeter. Body Mass Index (BMI) determined through the growth curves of the World Health Organization. Physical fitness variables (strength of upper and lower limbs, agility, speed and flexibility), were taken according to CELAFISCS standardization.
RESULTS:
Among male students it was found a prevalence of 23.2% obese, 44.4% overweight and 32.4% eutrophic. Among females, the values were: 30.9% obese, overweight 39.5% and 20.6% eutrophic. When analyzing the prevalence of valgus according to the BMI classifications it was, found a significant positive association in both sexes. Association was found between genu valgum and upper limbs strength only in crude analysis. The other variables, agility, speed and flexibility were not associated even when the analysis was adjusted.
CONCLUSION:
there was a positive association between malalignment of the knees, body mass index and physical fitness among schoolchildren.
Genu Valgum; Physical Fitness; Child
OBJETIVO:
Verificar associação entre o mau alinhamento de joelhos (geno valgo) e variáveis de aptidão física em estudantes.
MÉTODOS:
Foram analisados dados coletados entre 2000 a 2009. A amostra foi composta por 1.141 estudantes de ambos os sexos, de 6 a 18 anos. Para participar da pesquisa os estudantes deveriam atender os seguintes critérios: ter entre 6 e 18 anos e uma avaliação completa da aptidão física, incluindo a medida de geno valgo. O valgismo foi determinado pela distância intermaleolar, com régua em centímetros. Já para a classificação do Índice de Massa Corporal (IMC) usaram-se as curvas de crescimento da Organização Mundial da Saúde e as variáveis de aptidão física analisadas (força de membros inferiores e superiores, agilidade, velocidade e flexibilidade) seguiram a padronização CELAFISCS.
RESULTADOS:
No sexo masculino foi encontra uma prevalência de 23,2% de obesos, 44,4% com excesso de peso e 32,4% eutróficos. Entre o sexo feminino, 30,9% eram obesas, 39,5% com excesso de peso 39,5% e 20,6% eutróficas. Quando analisada a prevalência de valgismo de acordo com as classificações do IMC, foi encontrada associação positiva e significativa em ambos os sexos. Foi encontrada associação entre geno valgo à força de membros superiores apenas na análise bruta. As demais variáveis não apresentaram associação.
CONCLUSÃO:
Houve associação positiva entre mau alinhamento dos joelhos, índice de massa corporal e aptidão física em estudantes.
Geno valgo; Aptidão física; Criança
Introduction
Data from around the world have demonstrated increasing prevalence of obesity, not only among the adult population but also among young adults and adolescents.1 This increase is strongly associated with two main factors, among other causes: low levels of physical activity and increased intake of highly calorific foods.2,3
Regular practicing of physical activity may positively influence the levels of physical fitness.4 However, biomechanical and/or postural abnormalities such as knee misalignment seem to be one of the possible causes that may limit individuals' engagement in physical activities, given that in addition to the specific local alterations, these may affect other joints and limit the capacity for exercise.5
One of the deviations that most affect children and young adults is genu valgum. This knee misalignment is defined as displacement of the knees in relation to the proximal axis of the body, and it is more prevalent among girls. In cases of high degrees of valgus, this may directly influence performance relating to neuromotor variables of physical fitness, such as speed and agility, and also anthropometric variables like body adiposity.6
Some hypotheses have suggested that overweight and obese individuals would have greater likelihood of presenting postural deviation (genu valgum).7,8 On the other hand, other authors have suggested that higher degrees of genu valgum may have implications for maintaining a physically active lifestyle, thereby increasing the chances of presented greater-than-expected weight.9
The objective of the present study was to analyze the association between genu valgum, body mass index and physical fitness among students at public schools.
Methods
The present study forms part of the Mixed Longitudinal Growth and Development Project of Ilhabela, which has been developed by CELAFISCS since 1978. In this, the impact of the growth and development process on physical fitness variables among children in the municipality of Ilhabela (São Paulo, Brazil) is studied.
This project makes semestral assessments, always in April and October, and includes anthropometric, metabolic, neuromotor, nutritional and, more recently, physical activity level measurements. To make up the sample for the present study, a database of more than 3,500 children and adolescents of both sexes who participated in evaluations between 2000 and 2009 was analyzed. Among these subjects, 1,141 met the inclusion criteria used, i.e. they were between 6 and 18 years of age and a complete assessment of physical fitness, including measurements of genu valgum, were available. This project was approved by the Ethics Committee of the Universidade Federal de São Paulo, under protocol n# 0056/10.
Knee misalignment (genu valgum) was assessed with the students in an upright standing position, with observation in the posteroanterior direction, using a rule marked out in centimeters (cm). The intermalleolar distance was measured in cm as recommended by Heath and Staheli.10
Body mass measurements were obtained using a digital scale with precision of 100 grams, with the individual wearing as little clothing as possible. Height was measured using a stadiometer, in cm, and was calculated as the average of three measurements. To calculate the body mass index (BMI), the above two measurements were used and the subjects were classified as eutrophic, overweight or obese, in accordance with the criteria proposed by the World Health Organization.11
Lower-limb strength was measured by means of the vertical impulse test, without aid from the upper limbs (cm), and three attempts were made. To measure upper-limb strength, the hand grip test was used with a dynamometer (kg). The variable of agility was measured using the "shuttle run" test (seconds), with two attempts. For the speed test, running over a distance of 50 meters (seconds) was used, with a single attempt. Flexibility was estimated (cm) using the "sit and reach" test.12
All the measurements and tests followed the standardization of CELAFISCS13 and took into consideration the best result from each test. The reproducibility and objectivity values for each measurement made between the years ranged from 0.96 to 0.99 for body mass, 0.97 to 0.99 for height, 0.51 to 0.97 for upper-limb strength, 0.62 to 0.92 for lower-limb strength, 0.58 to 0.89 for agility, 0.61 to 0.91 for flexibility and 0.58 to 0.92 for speed, respectively.
Statistical analysis
The descriptive analyses were detailed by means of absolute numbers and proportions for categorical data. Bivariate analyses between the physical activity level and independent variables were conducted using chi-square tests for heterogeneity (categorical variables) and for linear trend (ordinal variables). To analyze the physical fitness variables, increasing terciles were created because classification criteria existed for the variables used in the present study.
Analyses adjusted for possible confounding factors were performed by means of Poisson regression with robust adjustment of variance.14 The variables were selected by means of the "bottom-down" method.15 Variables with p values < 0.20 were retained in the final analysis model. The significance level used was p < 0.05. All the analyses were conducted by means of the Stata version 10.0 statistical package.
Results
The data for the present study was supplied by 1141 individuals who fulfilled the inclusion criteria. The mean age of the sample was 11.16 ± 2.65 years (boys 11.25 ± 2.74 and girls 11.09 ± 2.57). The mean BMI was 18.17 ± 3.27 kg/m2 (boys 17.92 ± 3.19 kg/m2 and girls 18.37 ± 3.31 kg/m2).
After adjusting for age and sex, the prevalence of obesity among the girls was 45% (95% CI: 1.21 - 1.74) greater than the prevalence of eutrophic individuals, while the prevalence among the boys was 34% greater (95% CI: 1.08 - 1.66) (Table 1).
Table 2 presents a description of the sample for all the independent variables and their associations with genu valgum. The prevalence of genu valgum encountered was 56.6% (95% CI: 53.7 - 59.4). Among females, the prevalence was 59.2% and among males, 53.6%. Among the girls, 20.6% were classified as eutrophic, 39.5% as overweight and 30.9% as obese. Among the boys, the values were 32.4% eutrophic, 44.4% overweight and 23.2% obese.
Analysis on associations with the degree of genu valgum showed that individuals with better performance in the lower-limb strength test presented lower prevalence of knee misalignment (p ≤ 0.001).
Table 3 shows the crude and adjusted analyses on the association between genu valgum and the independent variables. After adjustment for confounding variables, genu valgum was seen to be associated with age and BMI, with prevalence in the obese group that was 40% (95% CI: 1.22 -1.60) greater than among the eutrophic individuals.
An association was found between genu valgum and upper-limb strength was only found in the crude analysis. The other variables (agility, speed, lower-limb strength and flexibility) did not present any association even when the analysis was adjusted (Table 3).
Fig. 1 presents a correlation between the degree of genu valgum (percentiles) and BMI. The proportion of the individuals classified in the percentile ≥ 75 was greatest among the obese subjects (p < 0.001). The lowest BMI (eutrophic individuals) presented a significant association with lower degree of genu valgum, i.e. the greater the degree of valgus was, the greater the obesity was; and reciprocally, the lower the degree of valgus was, the lower the degree of adiposity was.
Association between degree of genu valgum and body mass index among students in Ilhabela, SP.
Discussion
The Longitudinal Growth, Development and Physical Fitness Project among students in Ilhabela has provided an important original line of approach on posture that has sought to correlate postural deviation with motor performance and anthropometric, neuromotor, metabolic and physical activity characteristics. The results found in the present study showed that there was a significant association between genu valgum and physical fitness variables among students of both sexes in Ilhabela. In addition to the present study, other authors9,16,17 have also undertaken research projects among students in Ilhabela, showing correlations between physical fitness and the intermalleolar and intercondylar distances among students in Ilhabela.
A study that analyzed 274 students of both sexes aged 7 to 18 years found a significant association between the degrees of genu valgum and the physical fitness variables (body mass, agility and speed).9 In the same study, the prevalence of genu valgum found was 68.6%, and the authors observed that the young people who presented greater degrees of valgus had deficits of 10% in speed tests.
Martinelli et al.18 found that the prevalence of genu valgum was 87% among overweight children of both sexes aged 5 to 9 years. These authors did not find any statistical difference between the sexes. According to Gomes et al.,19 the prevalence of genu valgum varied over the years, with a relationship with different developmental stages.
According to Cardoso et al.,5 Gomes et al.,19 MacMahon et al.20 and Arazi et al.,21 in addition to knee alignment variations (valgus, varus or neutral)with age among normal children, the prevalence of genu valgum is greater during infancy, especially between the ages of 2 to 6 years. These authors stated that high degrees of genu valgum might have implications for maintaining a physically active lifestyle among children and adolescents. Through this, the chances that such children would present greater-than-expected weight would be higher. This hypothesis was supported by the findings from the present study.
Joao et al.22 measured the angling of the knees using a goniometer and the distance between the malleoli using a measuring tape, in a study on 79 children aged 7 to 10 years. These authors observed that the group of obese subjects presented greater prevalence of valgus knee in the two methods of evaluation.
A literature review study demonstrated that valgus and varus knee deformities may give rise to lower-limb dysfunction that has important consequences for activities of daily living, such as walking, sitting down and getting up, and going up and down stairs.23,24
It is extremely important to emphasize that the results from the present study and from other studies conducted so far9,16,24,25 only show a relationship between the intermalleolar and intercondylar distances and the obesity and physical fitness variables in children and adolescents.
According to some authors,23,26 obese adolescents have been shown to present localized orthopedic alterations, particularly in the lower limbs, such as genu valgum. Jannini et al.23 conducted a cross-sectional study among eutrophic and obese adolescents. They concluded that obesity may cause damage to the osteoarticular system at the beginning of adolescence.
According to Calvete,27 obesity causes mechanical overload on the locomotor apparatus and postural misalignment with ante-riorization of the center of mass, thus leading to functional alterations in the lower limbs and increased mechanical need for adaptation to the new corporal regime. Yaniv et al.28 conducted a study among young athletes and found that there were greater postural alterations among older athletes than among younger ones, which may have indicated that the occurrences of changes to the alignment of the lower limbs resulted from sports practice. However, these authors made it clear that further studies using different methods would be needed in order to obtain a broader view regarding the causes of axial deformity.
According to Matsudo6 and Garcia et al.,9 genu valgum was more prevalent among girls, which could be in physiologically lighter cases, but in cases of greater intensity and during adolescence there would be greater implications regarding anthropometric and neuromotor fitness, and particularly in relation to adiposity and running for 50 m.
We consider that the present study has certain limitations: there was a lack of criteria for classifying genu valgum; this was a cross-sectional cohort study that did not allow a cause-effect relationship to be established; and no control was made for biological maturity and age, which is an important factor given that postural deviations of the lower limbs undergo modifications with the passing of the years.
Conclusion
Within the limitations of a cross-sectional study, the present findings confirm the hypothesis of a positive association between knee misalignment, body mass index and physical fitness among students. Further studies with appropriate designs that might show a possible cause-effect relationship between the variables analyzed in the present study are needed.
REFERENCES
-
1Wang Y, Lobstein T. Worldwide trends in childhood overweight and obesity. Int J Pediatr Obes. 2006;1(1):11-25.
-
2He Q, Wong T, Du L, Jiang Z, Yu TI, Qiu H, et al. Physical activity, cardiorespiratory fitness, and obesity among Chinese children. Prev Med. 2011;52(2)109-13.
-
3Singhal A, Kennedy K, Lanigan J, Fewtrell M, Cole TJ, Stephenson T, et al. Nutrition in infancy and long-term risk of obesity: evidence from 2 randomized controlled trials1-3. Am J Clin Nutr. 2010;92(5)1133-44.
-
4Kristensen PL, Moeller NC, Korsholm L, Kolle E, Wedderkopp N, Froberg K, et al. The association between aerobic fitness and physical activity in children and adolescents: the European youth heart study. Eur J Appl Physiol. 2010;110(2):267-75.
-
5Cardoso ALS, Tavares A e Plavnik FL. Aptidão física em uma população de pacientes hipertensos: avaliação das condições osteoarticulares visando a benefício cardiovascular. Rev Bras Hipertens. 2008;15(3):125-32.
-
6Matsudo V. Lesões e alterações osteomusculares na criança e no adolescente atleta. In: De Rose Júnior D. Esporte e atividade física na infância e na adolescência. Porto Alegre: Artmed; 2ª ed, 2009. p. 197-209.
-
7Cicca LO, Joao SMA e Sacco ICN. Caracterização postural dos membros inferiores de criancas obesas de 7-10 anos. Fisioter Pesqui. 2007;14(2):40-6.
-
8Wearing SC, Hennig EM, Byrne NM, Steele Jr, Hills AP. The impact of childhood obesity on musculoskeletal form. Obes Rev. 2006;7(2):209-18.
-
9Garcia N, Matsudo SM, Matsudo VKR. Relação entre aptidão física e geno valgo em crianças e adolescentes. In: Anais XXIII Simpósio Internacional de Ciências do Esporte. São Paulo, Brasil, 2000, p.142.
-
10Heath CH, Staheli LT. Normal limits of knee angle in white children-genu varum and genu valgum. J Pediatr Orthop. 1993;13(2):259-62.
-
11De Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. B World Health Organ. 2007;85(9):660-7.
-
12Wells KF, Dillon EK. The sit and reach a test of back and leg flexibility. Res Q Exerc Sport. 1952;23(1):115-8.
-
13Matsudo VKR. Testes em Ciências do Esporte. São Paulo: Centro de Estudos do Laboratório de Aptidão Física de São Caetano do Sul; 7ªed, 2005.
-
14Barros AJ, Hirakata VN. Alternatives for logistic regression in cross-sectional studies: an empirical comparison of models that directly estimate the prevalence ratio. BMC Med Res Methodol. 2003;3(1):21.
-
15Dumith SC. Proposta de um modelo teórico para a adoção da prática de atividade física. Rev Bras Ativ Saude. 2008;13(2):110-20.
-
16Oliveira AC, Andrade DR, Matsudo VKR, Oliveira LC. Relação entre geno varo e aptidão física em estudantes de baixo nível socioeconômico. R Bras Ci e Mov. 2009;17(1):7-14.
-
17Rezende LFM, Araújo TL, Santos M, Matsudo VKR. Does soccer lead to genu varum? In: American College of Sports Medicine. 57th Annual Meeting. Baltimore: Med Sci Sports Exerc; 2010.
-
18Martinelli AR, Purga MO, Mantovani AM, Camargo MR, Rosell AB, Fregonesi CEPT, et al. Análise do alinhamento dos membros inferiores em crianças com excesso de peso. Rev Bras Cineantropom Desempenho Hum. 2011;13(2):124-30.
-
19Gomes CTS, Keiserman LS, Kroeff MAH, Crestani MV. Variação das distâncias intermaleolar e intercondiliana nos jovens. Rev Bras Ortop. 1997;32(12):963-6.
-
20MacMahon EB, Carmines DV, Irani RN. Physiologic bowing in children: an analysis of the pendulum mechanism. J Pediatr Orthop B. 1995;4(1):100-5.
-
21Arazi M, Ogun TC, Memik R. Normal development of the tibiofemoral angle in children: a clinical study of 590 normal subjects from 3 to 17 years of age. J Pediatr Orthop. 2001;21(2)264-7.
-
22João SMA, Cicca LO, Cunha ACP. Avaliação postural do joelho de crianças obesas de 7 a 10 anos. In: Anais 13º Simpósio Internacional da Iniciação Científica da Universidade de São Paulo. Ribeirão Preto; 2005, p. 2090.
-
23Jannini SN, Dória-Filho U, Damiani D, Silva CAA. Dor músculo-esquelética em adolescentes obesos. J Pediatr. 2011;87(4):329-35.
-
24Gama AEF, Lucena LC, Andrade MM, Alves SB. Deformidades em valgo e varo de joelhos alteram a cinesiologia dos membros inferiores. In: X Encontro de Iniciação à Docência da Universidade Federal da Paraiba, Paraiba; 2007.
-
25Neves MC, Campagnolo JL. Desvios axiais dos membros inferiores. Rev Port Clin Geral. 2009;25:464-70.
-
26Gettys FK, Jackson JB, Frick SL. Obesity in pediatric orthopaedics. Orthop Clin North Am. 2011;42(1):95-105.
-
27Calvete AS. A relação entre alteração postural e lesões esportivas em crianças e adolescentes obesos. Motriz. 2004;10(2):67-72.
-
28Yaniv M, Becker T, Goldwirt M, Khamis S, Steinberg D, Weintroub S. Prevalence of bowlegs among child and adolescent soccer players. Clin J Sport Med. 2006;16(5):392-6.
Publication Dates
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Publication in this collection
Jan-Feb 2013
History
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Received
15 Sept 2011 -
Accepted
25 Oct 2011
