This is a quantitative, exploratory, cross-sectional study approved by the Research Ethics Committee of Universidade Federal dos Vales do Jequitinhonha e Mucuri UFVJM (Protocol: 2.773.418), with written informed head parent consent and participant assent. All methods were carried out in accordance with relevant guidelines and regulations in the manuscript. Data collection took place from July to December 2019. Pre-school children, that is, children from 3 to 5 years old, from public schools in a Brazilian municipality, were eligible.
Exclusion criteria were: preterm and low birth weight infants; infants with pregnancy and delivery complications; infants with signs of malnutrition or illness that interfere with growth and development; and infants who had been subject to an infectious process (such as fever, influenza, and diarrhea) in the previous 21 days.
The sample size was based on a pilot study with five children in each group, in which a minimum difference of 2.70 was found between the groups for Locomotor subtest standard scores of the TGMD2, with a standard deviation (SD) of 3.50. For sample calculation, a power of 90%, and an alpha error of 5% were considered, with 20 participants thus being required for each group, totaling 40 subjects.
For the assessment of body composition, total body mass was measured and body fat mass was found using dual energy radiological absorptometry (DEXA) (Pediatric medium scan mode software, Lunar Radiation Corporation, Madison, Wisconsin, USA, model-DPX).
Weight and height measurements were taken during the study visits. The children’s weight was measured to the nearest 0.1 kg with an electronic scale. The standing height of the children was measured to the nearest millimeter with a wall-mounted stadiometer. The children removed their shoes and socks before stepping on the scale and were told to stand in an upright position when measuring height. Age-specific BMI was calculated as body weight (kg) divided by body height squared (m2) 16.
Considering the high correlation found between the amount of body fat mass and BMI (r = 0.90, p = 0.00), and according to studies on body composition and BMI 15, participants were classified into groups according to BMI, following World Health Organization (WHO) recommendations. The WHO reference curves by gender and age were considered, using the calculation software WHO Anthro version 3.2.2 16. Children with a BMI < 85 were considered eutrophic and allocated to Group 1, whereas children with a BMI ≥ 97 were considered overweight/obese and allocated to Group 2.
Sex, age, socioeconomic status, maternal education13, PA10, quality of the home environment and quality of the school environment14 were collected for control.
Sociodemographic variables were collected using a specific questionnaire. To verify the economic level of families, the Brazil economic classification criterion, from the Brazilian Association of Research Companies was used. This is a questionnaire that stratifies the general economic classification resulting from this criterion from A1 (high economic class) to E (very low economic class) 17.
The quality of the environment in which the child lives was assessed using the Early Childhood Home Observation for Measurement of the Environment (EC_HOME) 18. The EC_HOME is applied through observation and semi-structured interviews during home visits, standardized for children aged 3 to 5 years. The instrument contains 55 items divided into 8 scales: I-Learning materials, II-Language stimulation, III-Physical environment, IV-Responsiveness, V-Academic stimulation, VI-Modeling, VII-Variety, VII-Acceptance. For analysis, the sum of the raw scores of the subscales was used.
The quality of the school environment was assessed using the Early Childhood Environment Rating Scales (ECERS) 19, which contain inclusive and culturally sensitive indicators for many items. The scale consists of 43 items organized into 7 subscales (1-Space and Furnishings, 2-Personal Care Routines, 3-Language and Literacy, 4-Learning activities, 5-Interactions, 6-Program Structure, 7- Parents and staff). Each quality indicator was marked, considering its presence or absence in each collective environment (classroom), with the items scored from 1 to 7. The final score of the scale is given by the mean of the seven subscales. It is an ordinal, increasing scale, from 1 to 7, the interpretation of quality being 1: inadequate; 3: minimal (basic); 5: good; 7: excellent.
The PA level was measured using an accelerometer (Actigraph®- Model GT9X); for a period of 3 days, without including the weekend 21, for a minimum of 570 minutes a day 10, which is considered suitable for preschoolers 21. Accelerometers were initialized and analyzed using 5-second epochs. In all analyses, consecutive periods of ≥ 20 minutes of zero counts were defined as non-wear time 20, with a sampling rate of 60 Hz. The acceleration units were expressed in triaxial vector magnitude (VM). The accelerometer was positioned on the right side of the hip to capture accelerations and decelerations of the body and determine objective measurements of gross acceleration, intensity of physical activity, heart rate intervals and total time of suspension of use 20. Pediatric cutoff points validated for preschool children, with score values, classify as sedentary (0 to 819 counts / m), mild (820 to 3907), moderate (3908 to 6111) and vigorous (above 6612) 22. For this study, the child's mean time at these intensities was used. The classification adopted for “active” or “insufficiently active” was established according to the WHO, which considers an active child to be one who has a PA of at least 180 minutes/day, with a minimum of 60 minutes/day in moderate to vigorous PA 2.
In addition, information was gathered on environmental opportunities for active and sedentary behavior, such as the time of exposure to screens; the presence of internal (30 m2 per inhabitant) and external (backyard) physical space at home; and the presence of a playground at school, among other variables relevant to the study. The variable “time of exposure to screens” was classified considering the parents' report of the time in minutes that the child was exposed to a screen (television and cell phone) and later classified within the recommended limit (less than two hours) and above the recommended limit (two hours and over) according to the guidelines of the American Pediatric Association 23.
MC was measured using the Test of Gross Motor Development second edition (TGMD-2). The reference is based on a norm and criterion for the development of children between three and ten years old. It consists of 12 motor skills divided into two subtests, locomotor (run, leap, gallop, hop, jump, and slide) and object control (catch, strike, bounce, over and underhand throw, and kick). For each skill, specific motor criteria was observed, based on mature movement patterns referenced in the literature and by professionals in the field. The results obtained for each subtest were added and the raw scores were converted into normalized scores for sex and age with a mean of 100 ± 1524, validated for Brazilian children 25. For the study, the standardized scores described in Locomotor subtest standard scores (LS), Object Control subtest (OC) and Sum of the Gross Motor Quotient (GMQ) (which includes the LS and OC) were used. The reliability for TGMD2 showed intra-class correlation coefficients (ICC) of 0.895 for the LS, 0.925 for OC and 0.841 for GMQ.
All tests and measurements including body weight, height, assessment of gross MC, as well as questionnaires were applied by one trained examiner. The children were evaluated in the same places, following the order of previously defined evaluations, with an interval between collections of a maximum of 3 weeks.
The data were analyzed using the Statistical Package for the Social Sciences (SPSS version 2.2). First, the Shapiro-Wilk test was performed to assess data normality, followed by Levene's test to verify the homogeneity of the variance. Subsequently, the descriptive statistics of continuous variables were demonstrated as median (minimum and maximum) and mean (standard deviation), as appropriate. Subsequently, Chi-squared tests were applied to compare the proportion of eutrophic groups (G1) and overweight (G2). To verify differences between groups, the t-test for independent samples (for variables with normal distribution) or the Mann-Whitney test (for variables with non-normal distribution) was used.
Spearman's or Pearson’s correlation was performed to verify the relationship between body fat mass and gross motor competence variables, followed by the multiple linear regression model. Statistical significance was set at 5%. Since sex, age, maternal education, socioeconomic status, PA level, quality of the home environment and quality of the school environment could be confounding factors, the analysis was adjusted for these variables. A residual analysis showed a normal distribution and homogeneous variance in all regression models. The magnitude of the effect (d) was also verified.