EFFECTS OF A SMALL-SIDED SOCCER PROGRAM ON HEALTH PARAMETERS IN OBESE CHILDREN

ABSTRACT Introduction: Childhood obesity is increasing and, as a consequence, it generates health complications resulting from sedentary behavior and low levels of physical fitness. There are few studies involving children, metabolic and cardiorespiratory profiles, and soccer. Objective: The purpose was to measure the effects of a 12-week recreational small-sided soccer program on cardiometabolic risk and individual responses to cardiometabolic risk factors in overweight or obese boys. Methods: Thirteen boys aged 8-12 years (34.9±11.6% body fat) participated in a 12-week recreational small-sided soccer training program with two 80-minute sessions per week at intensities over 80% of the maximal heart rate. Anthropometric characteristics, cardiorespiratory fitness, metabolic profile, individual responses to peak oxygen uptake (VO2peak), maximal workload (Wmax), fasting blood glucose, insulin, HOMA-IR, LDL-C, HDL-C, TC, and TG were measured both pre- and post-training. Results: Considering the individual responses of the participants, recreational soccer training was effective in improving variations in maximum power and exhaustion time, as well as promoting at least one beneficial change in cardiometabolic risk factors in 84% of the overweight or obese children. There were no differences between pre- and post-program anthropometric characteristics, metabolic profiles, or VO2peak values. Conclusion: Twelve-week recreational small-sided soccer programs were able to improve maximal power and anaerobic capacity and maintain cardiometabolic risk factor levels in overweight and obese boys. Level of evidence I; High-quality prospective study (all patients were enrolled at the same stage of disease, with >80% of patients enrolled) .


INTRODUCTION
The global obesity epidemic has been considered a major public health concern, mainly due to the increased risk of several serious chronic diseases, such as diabetes, hypertension, cancer, and dispinea. 1 Childhood obesity arises from a combination of factors, including insufficient physical activity (PA). 2 Because of that, group sports have emerged as a potential intervention to increase the PA. 3,4 However, little is known about the benefits of group sports on cardiometabolic risk factors (high blood pressure, lipemia, glycemia, insulin resistance, and low physical activity and fitness) and health-related physical fitness (cardiorrespiratory and muscular fitness) in children with overweight or obesity.
Inadequate physical activity has been linked to an increased risk of childhood obesity, 2 and soccer is one of the most popular sports in the world, and it can improve body composition, 3,5 biochemical markers 3,4 handgrip strength, 6 and cardiorespiratory responses. [3][4][5][6][7] Likewise, soccer training is considered all-in-one training with broad-spectrum fitness and can provide an important alternative for the treatment of childhood obesity. 8 Obesity has multifactorial causes, and individual responses to training programs should be considered even when exercise is performed in groups. In the era of personalized medicine, interindividual differences in the magnitude of response to an exercise training program (individual response) have received increasing scientific interest. [9][10][11][12] Individuals under similar stimulus may achieve different benefits after an exercise training program and are considered responders (R), while those whose responses remain unchanged or worsen are considered non-responders (NR). 11 For this reason, the aim of the present study was to measure the effects of a 12-week period recreational soccer program on cardiometabolic risk factors (fasting lipemia, fasting blood glucose, fasting insulin, homeostatic model assessment for insulin resistance (HOMA-IR), VO 2 peak, and maximal workload (Wmax) factors and individual responses in boys with overweight or obesity.

MATERIALS AND METHODS
Thirteen boys aged between 8 and 12 years were recruited for this quasi-experimental study investigating the effects of a 12-week recreational small-sided soccer program. All subjects performed only physical education at school and were instructed to maintain their daily habits during the intervention. The study was approved by the University Research Ethics Board (Case Project ID #: 53943116300005347) and was conducted in compliance with the standards set by the Declaration of Helsinki. Boys and their legal guardians were informed of the experimental protocol and the potential risks and provided written informed consent prior to participation.

Inclusion and exclusion criteria
The study included boys with overweight or obesity defined by the criteria: body mass index Z-score (BMI Z-score) ≤ 2 standard deviation (SD) were classified as overweight (four boys) and BMI Z-score > 2 SD were classified as obese (nine boys) 13,14 and who were enrolled in the school system. Boys who had some incapacity to perform physical exercise or who used medication that could influence the study results were excluded.

Anthropometric Measures and Maturity Status
Body mass, height, and sitting height were assessed using a digital scale and a stadiometer (Urano PS 180A, 0.1 kg and 0.01-m resolution; Rio Grande do Sul, Brazil), respectively. These values were used to calculate the BMI using the following equation: body mass (kg)/height 2 (m). A total of eight skinfolds (mm) were measured: triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh, and medial calf (Skinfold Caliper Mitutoyo-CESCORF, Porto Alegre-RS, Brazil). 15 Landmarks for each skinfold and waist-circumference measurement were in accordance with previously described procedures. 15 The equations proposed by Slaughter et al. 16 were used to estimate the body fat and fat free mass percentages. The sitting height was used to estimate years of peak height velocity according to Mirwarld et al. 17

Cardiorespiratory Fitness
An incremental exercise test was performed, using the McMaster All-Out Progressive Continuous Cycling Test. 18,19 The test began at 25 W and had 25-50-W increments every 2 min, according to the participant's height, while maintaining a cadence between 60 and 80 rpm. Measurements of expired VO 2 and VCO 2 were made continuously using calibrated metabolic equipment (Quark CPET, Cardio Pulmonary Exercise Test, COSMED-Italy). Peak was considered the greatest oxygen uptake (VO 2 ) value in the whole protocol. The participants were verbally encouraged during the test to achieve their maximal performance. To be considered an exhaustive effort, each participant had to satisfy at least two of the following criteria upon termination of the cycle ergometer test due to volitional exhaustion: (1) VO 2 plateau, defined as an increase in VO 2 of less than 2.1 mL . kg -1. min -1 accompanied by an increase in exercise intensity. 20 (2) At the end of the test, the heart rate was 95% of the predicted maximal heart rate. [208 -(0.7 x age)] = HRmax, 21 (3) respiratory exchange ratio (RER) ≥ 1.0, 22 (4) despite strong verbal encouragement, inability to maintain a cycling cadence above 60 rpm. 18 Heart rate was measured using a heart rate monitor (Polar, S610 USA). Participants should have demonstrated overt signs of extreme physical exertion, such as facial flushing and grimacing, sweating, hyperpnea, and unsteady gait, at the end of the test. 22 The Wmax was considered as the workload correspondent to the last stage completed of the incremental exercise test. W max was considered an indicator of muscular fitness.

Metabolic measures
For the biochemical analysis, fasting blood glucose, fasting insulin, triglycerides (TG), total cholesterol (TC), HDL cholesterol (HDL-C) and LDL cholesterol (LDL-C) were collected after 10 to 12 hours of fasting. An 8 mL sample of blood was collected by venipuncture and stored in tubes with specific anticoagulant gel (EDTA). After this procedure, the samples were centrifuged at 3.500 rpm for 10 min, and the aliquots of plasma were stored at -80°C for posterior analysis. Blood glucose, TG, TC, and HDL-C were determined by enzymatic colorimetric tests (Cobas C111, Roche, Diagnostics, Basel, Switzerland). The fasting insulin was evaluated by kits for humans (DRG International, Springfield, USA) and determined by an enzyme linked immunosorbent assay (ELISA). The insulin resistance was estimated using the homeostasis model assessment of insulin resistance: HOMA-IR is an abbreviation for [fasting blood glucose (mmol . L -1 ) fasting insulin (uU . ml -1 )] 22.5. The LDL-C was estimated using the equation by Friedewald: (LDL-C: CT HDL-C TG 5).

Responders and non-responders' classification
The percentage of responders and non-responders was obtained according to previous studies, considering Δ% effect (% of the after minus the before value). 9,10,12 To consider acceptable clinical and individual effects, we used the Δ% values obtained in previously published studies with public and metabolic parameters similar to the present study, defining cut off points such as: TG (the cut-off points − 10.1 mg . dL -1 , R>10%), TC (change of the cut points − 7.7 mg.dL -1 , R>5%), HDL-C (change of the cut-off points 4.2 mg . dL -1 , R>10%), LDL-C (change of the cut-off points − 12.4 mg . dL -1 , R>10), and HOMA-IR (change of the cut-off points − 1.0, R>30%). 12

Recreational Small-Sided Soccer Training Program
Thirteen boys participated in a 12-week recreational small-sided soccer training program with two sessions per week. The training lasted 90 minutes and was divided into the following sections: warm-up (10 minutes) with playful games; technical drills (15 minutes) to learn specific fundamentals (pass, kick, ball control, etc.); small-sided soccer games (20 to 40 minutes) with adapted games beginning with [2 vs. 2, 3 vs. 3, 4 vs. 4, 5 vs. 5] and its variations with changes in the size of the court to give the game dynamics; and a cool-down (5 minutes). For the main part, there was an increase in the volume of free game time, with intervals of 1 to 3 minutes for recovery every 5 minutes of game. During the first four weeks, there were 20 minutes of small-sided soccer games, increasing to 30 minutes the following four weeks and then to 40 minutes the last four weeks. The intensity of training was monitored at the end of each activity (warm-up, technical drills, small-sided soccer games) using a heart rate monitor. During small-sided soccer games, boys were monitored to maintain a heart rate of over 80% of their HRmax obtained in the maximal incremental exercise test. All participants had to complete 80% of the training sessions. Those subjects with three consecutive absences did not have their data computed. All participants were instructed not to change their regular physical activity habits during the experiment.

Statistical analysis
Data normality and data homogeneity were verified through Shapiro--Wilk and Levene's tests, respectively. Paired T-tests were used to compare the pre-test with the post-test results. The data are presented as mean standard deviation.Measures of the effect size were calculated by Cohen´s d test, and the magnitude of the effect size was classified according to the following criteria: d < 0.2 was considered "trivial, " 0.2-0.59 was considered "small, " and 0.6-1.19 represented "moderate, " 1.2-1.99 was considered "high", 2.0-3.9 was considered "very high" and > 4 constituted "close to perfect". 23 A significance level of 0.05 was adopted for all statistical tests, and the Statistical Package for the Social Sciences (SPSS) version 20.0 was used.

RESULTS
Anthropometric characteristics pre-and post-training are described in Table 1. A higher W max and an increased time to exhaustion in cardiorespiratory fitness test were significant after 12-week period. No significant differences were found between pre-and post-recreational program for fasting blood glucose, fasting insulin, HOMA-IR, TC, TG, LDL-C, HDL-C and VO 2 peak .. The data are described in Table 2. Figure 1 depicts individual responses for cardiometabolic risk factors. In this study, 46% boys were considered responders for CT; 38% for LDL-C; 23% for HDL-C, TG and HOMA-IR, respectively. Figure 2 shows the individual responses for each participan on HOMA and lipemic profile.

DISCUSSION
Recreational soccer training was effective after 12 weeks in improving maximum power and exhaustion time, as well as promoting at least one beneficial change in cardiometabolic risk factors in 84% of children with overweight or obesity, when individual responses were taken into account.The percentage of individuals considered responders was 46% for TC, 38% for LDL-C, 23% for HDL-C, TG, and HOMA-IR, respectively. Understanding individual responses is important due to the complexity of obesity treatment, and we can propose a beneficial approach to controlling childhood obesity as there is a lack of studies reporting the effects of individual and group sports interventions on cardiometabolic risk factors in preschool boys with overweight or obese pubescents.
We found a moderate and significant effect size in the time to exhaustion and maximum load in the maximum cycle ergometer test, indicating a greater tolerance to fatigue. Children showed significant gains with an increase of 1 min 21 sec in the total test time and reached a maximum load greater than 20w compared to the pre-training period. The answers can be linked to peripheral improvements. The activities performed by soccer training, such as sprints, kicking, and changes of direction, are related to mitochondrial adaptations, muscle capillarization, enzymatic activity, and neuromuscular adaptations, movements that create power and improve peripheral adaptations that seem to precede central adaptation. 24 Table 1. Anthropometric measures pre-and post-recreational soccer training program.

Variables
Pre   The increase in anaerobic metabolic pathway and muscular fitness is in accordance with the literature, where it has been seen that soccer intervention stimulates and increases the resistance of children by 22% after six weeks, while activities of low-moderate intensity and without training structure seem not to induce positive adaptations. 25 In the present study, we found an increase of 29% in Wmax achieved during cardiopulmonary exercise testing. In a similar group to the present study (children with obesity), after six months of training, Faude et al. 26 also found a 7% increase in Wmax achieved after soccer training, whereas the group that performed aerobic exercise increased 6%. These responses seem to be independent of the weekly training frequency since both the present study and Faude et al. 26 led to increased muscular fitness with two and three times a week.
In the present study, no significant differences among pre-and post-recreational small-sided soccer programs were found for HOMA-IR, lipemia, and VO 2 peak average. It is important to note that boys already had lipemia values considered normal for their age prior to soccer training. In that regard, obesity is a progressive, chronic inflammatory process and the results indicate that a recreational soccer program was able to prevent changes in cardiometabolic risk factors.
In relation to individual response, our findings indicate that 23% of boys were responders to HOMA-IR and improved insulin sensitivity, indicating that interventions with high exercise intensity (85%HRmax) can contain the progress of the inflammatory process. 3,9,12 Regarding body fat, subjects who showed greater adiposity reductions were those who improved insulin sensitivity and HOMA-IR, indicating that interventions with high exercise intensity can improve body composition, promoting health benefits. 3,27 For children with overweight or obesity, poor cardiorespiratory fitness is related to poor physical fitness values, high rates of chronic diseases, and mortality. 28 There were no significant differences in cardiorespiratory fitness measured by VO 2 peak before and after the soccer program. A possible explanation is that even with a high intensity close to the anaerobic threshold, the soccer program duration and weekly frequency may have been insufficient to improve health indicators more effectively. 2 Seabra et al. 4 found a 11.3% increase in VO 2 peak in boys (11 years) and Vasconcellos et al. 3 found an increase of 31% in adolescents (13 years) with intervention three times a week.
In relation to the children's responses to VO 2 peak, the results are still controversial because, many factors, such as chronological age, biological maturation, body composition, as well as genetic and environmental factors, can influence cardiorespiratory fitness, 29 and we are not aware of studies that have evaluated individual cardiorespiratory responses (responders and non-responders) in children after participating in a recreational soccer program.
This study presents strengths, such as a small 12-week soccer recreational program, twice a week, that could improve anaerobic capacity and present beneficial responses for the control of obesity. In addition, it highlights that some individuals need a greater load or training volume to reduce cardiometabolic risks. However, the study has some limitations, such as the absence of a control group that could bring more effective responses regarding training responses and the relatively small sample size, in which even after performing a sample calculation, the study sample loss was significant and limited the answers found.
It was concluded that twelve weeks of small-sided recreational soccer programs were able to improve maximal power, anaerobic capacity, and maintain cardiometabolic risk factor levels in overweight and obese boys.