Journal of Childhood

Introduction
hildhood obesity has become a global epidemic, posing a multifaceted challenge to public health systems worldwide. In the 21st century, the prevalence of overweight and obesity among school-age children has increased dramatically, serving as a critical precursor to debilitating metabolic conditions, including type 2 diabetes, cardiovascular disease, hypertension, and obstructive sleep apnea. Beyond these physiological risks, obesity imposes a significant psychological burden, often resulting in reduced self-esteem, social stigma, and a substantial decline in health-related quality of life. 
From a biomechanical perspective, excess adipose tissue acts as a mechanical load that severely impairs motor efficiency and coordination. Agility, defined as the ability to change direction quickly and accurately, is an essential factor for both athletic performance and the safe execution of daily physical activities. In obese children, the combination of increased body mass and decreased relative muscle strength often leads to reduced agility. Consequently, deficits in agility act as a deterrent to athletic participation, extending beyond simple motor limitations. This situation fosters a sedentary lifestyle, creating a vicious cycle in which inactivity and increasing weight gain mutually reinforce each other.
Since conventional, high-impact exercises are often inappropriate for this population due to excessive stress on growing joints, there is a pressing need for low-impact, engaging interventions. Rebound training offers a unique solution; its elastic surface absorbs a significant portion of the impact while providing high-intensity stimulation to the cardiovascular and atrial systems. By challenging proprioception and neuromuscular control, trampoline exercises can strengthen the motor pathways necessary for agility. Despite these potential benefits, empirical evidence regarding standard rebounding protocols for obese elementary school students remains limited. Therefore, this study aimed to investigate the effect of an 8-week rebounder training program on agility and body composition in obese girls aged 10 to 12 years.
Research Methods 
This quasi-experimental study employed a pre-test-post-test design with a control group. The statistical population comprised all elementary school students (grades 4-6) in Karaj city during the 2023-2024 academic year. Through convenience sampling, 30 obese girls aged 10-12 years, with a body fat percentage exceeding 26%, were selected and randomly assigned to two groups: an experimental group and a control group (15 participants in each). Inclusion criteria stipulated no history of cardiovascular or orthopedic disorders.
The experimental group engaged in an 8-week structured rebounding protocol, comprising 24 sessions (3 sessions per week, each lasting 50-60 minutes). Each session included a 10-minute warm-up, a 35-40 minute main workout phase (incorporating butterfly movements, burpees, and star jumps on the rebounder), and a 10-minute cool-down. The control group maintained their usual daily activities without any additional training. 
Agility was assessed using the Semenick test (1990), and body fat percentage was estimated via the three-point skinfold thickness method (measuring the triceps, suprailiac, and thigh sites) and calculated using the Siri equation. Statistical analysis was conducted using analysis of covariance (ANCOVA) with SPSS version 24, setting the significance level at P<0.05.
Results 
Before the intervention, no significant difference was observed between the two groups in terms of age, height, weight, and body mass index, indicating homogeneity of the groups. After the 8-week intervention, the results showed a significant improvement in the experimental group compared to the control group. Regarding body composition, the mean body fat percentage of the experimental group decreased from 29.4 to 26.98. The ANCOVA results for body fat percentage showed a significant difference between the groups (P<0.001, F=1.27/14.61) with an effect size of 64, indicating that 64% of the variance in body composition post-test scores was due to rebounding exercises. For agility, the experimental group showed a significant decrease in t-test time and improved from 16.26 seconds to 14.53 seconds. Analysis of covariance for agility also confirmed a significant difference between the groups after the end of the training period (P<0.001, F=1.27588/37). Based on the results, rebounder training could produce a significant improvement in the agility of the experimental group. The effect size indicates that 58% of the variance in agility post-test scores can be attributed to rebounding exercises.


Conclusion 
The findings of this study support the hypothesis that rebounding training is an effective method for improving agility and body composition in obese children. The observed improvement in agility can be attributed to the unstable nature of the trampoline surface, which necessitates continuous neuromuscular adjustments for balance maintenance. This dynamic environment stimulates the proprioceptive system and enhances motor unit synchronization, thereby enabling more efficient changes in direction. Furthermore, the low-impact characteristic of the rebounder allows obese children to perform high-frequency movements that would otherwise be painful on hard surfaces. 
The reduction in body fat percentage is likely a consequence of the high metabolic demands inherent in the training protocol. Rebound training facilitates fat oxidation while preserving lean muscle mass through mechanical loading. This is particularly important for children as it promotes a healthy basal metabolic rate. 
However, the study has limitations, including a small sample size and the absence of long-term follow-up. These factors prevent a comprehensive understanding of the sustainability of the observed gains. Practically, these results suggest that school physical education programs should incorporate rebounding exercises as a safe and engaging alternative to traditional aerobic activities. Theoretically, this study contributes to the pediatric exercise science literature by highlighting how enjoyable interventions can circumvent psychological barriers to exercise in obese populations. Future research should investigate the effects of varying training intensities and explore potential psychological benefits, such as improved body image and self-esteem, stemming from the promotion of motor competence.
Ethical Considerations
Compliance with ethical guidelines
This study was conducted in accordance with the ethical principles outlined in the Master’s thesis of Payam Noor University (Proposal Code: 4982/D/169). Written informed consent was obtained from the parents of all participants prior to the commencement of the study. The privacy and confidentiality of the participants’ information were carefully maintained throughout the research process.

Funding
This research was conducted as an independent academic study and did not receive any specific grants or financial support from government, commercial, or non-profit organizations.
Authors contributions
Responsible for study design, statistical analysis, and overall supervision: Amir Hamzeh Sabzi; Data collection, implementation of intervention sessions, and preparation of the initial draft of the article: Asiah Askari.
Conflicts of interest
The authors declared no conflicts of interest.
Acknowledgments
The authors express their gratitude to the physical education teachers of Karaj, students, and parents who participated in this study.