Mohamed Souhaiel Chelly

This study examined the effects of motor imagery (MI) training, performed alone or in combination with muscle contractions, on quadriceps performance in junior soccer players. Forty-five players (14.1 ± 0.8 years) were randomly assigned to MI alone (EXP-1; n = 15), based on the Physical, Environment, Task, Timing, Learning, Emotion, Perspective (PETTLEP) model (3 sessions/week, 20–25 min/session), MI combined with muscle contractions (EXP-2; n = 15; 3 session/week, 35–45 min/session), and a control group (CG; n = 15). Physical performance was assessed via vertical jumps (countermovement jump [CMJ], squat jump [SJ], drop jump [DJ]) and maximal isometric knee extension strength. A two-way repeated-measures general linear model (time × group) was used to assess mean differences. If necessary, we used a Mixed ANCOVA (Analysis of Covariance) to control for the influence of important parameters after significant mean differences were observed at the first examination. After 12 weeks, relevant-significant (p < 0.05 and η_p² > 0.15) interaction effects were observed for all variables. The interaction effects ranged from η_p² = 0.40 (maximum strength left) to η_p² = 0.77 (DJ). Regarding DJ, we found only a partial group effect between CG and EXP-2 (p = 0.044). Significant partial effects for strength parameters were calculated for the average strength (CG vs. EXP-2: left: p = 0.008; right: p = 0.018) and for the maximal strength (CG vs. EXP-2: left: p = 0.046). These findings suggest that motor imagery training may improve neuromuscular performance (maximal strength and vertical jump performance) in junior soccer players, whether performed alone or combined with muscle contractions.

Introduction: Plyometric training, reactive agility, and isometric training can improve lower limb muscle performance, although the effectiveness of their combination remains unknown in adolescent female handball players. This study compared the effects of 8 weeks of plyometric training combined with either reactive agility or isometrics. Methods: Female participants were randomly assigned to control (CONT; n = 12; 14.1 ± 0.4 years), Combined Plyometrics and Reactive Agility Training (CPRAT); n = 12; 13.9 ± 0.5 years), or Combined Plyometrics and Isometric Training (CPIT); n = 12; 13.9 ± 0.5 years) groups. The intervention groups trained twice/week for 8 weeks. Performance was assessed before and after the interventions using: 10 m sprint performance, Repeated-Change-Of-Direction (RCOD), Y-shaped agility, T-half, throwing velocity, countermovement jump (CMJ), maximal isometric force and rate of force development (RFD) of knee extension muscle tests. Upper and lower limb muscle volume was estimated anthropometrically. A 3 × 2 mixed analysis of variance was employed to examine the interaction effects (group x time). Results: CPRAT led to significantly greater RCOD improvements (p < 0.01) and T-half performance (p < 0.001). No significant difference was observed between CPIT vs. CONT. In contrast, (CPIT) showed significantly greater improvements in lower limb muscle volume and knee extension maximal isometric force (p < 0.05) than CPRAT or CONT. Results between experimental groups remained statistically unchanged for Y-Shaped Test, RFD, and lower and upper limb muscle volume. Results for both experimental groups remained statistically unchanged compared to CONT for 10 m sprints, throwing velocity, and CMJ height. Discussion: The CPRAT protocol is superior for developing multidirectional and reactive agility. The CPIT protocol maximizes isometric strength but has limited transfer to high-velocity dynamic tasks. The CPRAT procedure should be selected when the main purpose is to boost agility and COD. However, when developing lower-limb maximal strength is the primary goal, the CPIT treatment should be applied.

Background: The preschool years are a crucial period for development. Stable environments and responsive caregivers support children's cognitive and motor development, two interrelated and essential domains. Caregiver smartphone use in front of children may reduce attention and responsiveness, which have been negatively associated with young children's health and development. We examined associations between the frequency of caregiver smartphone use in a child's presence and motor skills and executive functions, and whether these associations vary by country income level. Methods: We analysed cross‐sectional data from 27 countries participating in the SUNRISE International Study. Caregivers reported the frequency of smartphone use in the child's presence across five scenarios: mealtime, playtime, travel, walk and bedtime routines. Children's motor skills were assessed using four established tests. Early Years Toolbox games were used to assess children's visual–spatial working memory and inhibition. Mixed‐effects linear regression models were used to assess the associations, including interaction terms to test variation by country income level. Models were adjusted for the child's sex, age, daily screen time, time spent outdoors, sleep duration and the caregiver's highest level of education. Results: The analytical sample included 2232 preschoolers (mean age = 4.2 ± 0.6 years, 50.9% girls). In fully adjusted models, the frequency of caregiver smartphone use in a child's presence was not associated with gross motor skills, fine motor skills, visual–spatial working memory or inhibition (all p > 0.05). Results did not differ by country income level. Conclusions: Findings suggest that the frequency of caregiver smartphone use in a child's presence alone may not be associated with performance on motor skills and executive function. There is a need for more sensitive measures that capture the frequency, duration and context of interruptions and more longitudinal studies that examine motor development and cognition. Future research should also account for socioeconomic and demographic diversity, environmental factors and cultural context when assessing such associations.

Purpose: This study aimed to evaluate the effects of a wearable resistance (WR) warm-up applied to the lower limbs as a preconditioning strategy for enhancing sprint performance in adolescent soccer players. Methods: Twenty elite male soccer players (< 15 years old) were randomly assigned to either a passive rest control group or one of three WR warm-up conditions: no load (WR-0), 5% body mass (WR-5), and 10% body mass (WR-10). The WR warm-up was conducted after a 20-m sprint task with the rate of perceived exertion (RPE) assessment. Other sprint tasks with RPE were conducted after the WR warm-up (before the game) and at the 5th and 45th min of the soccer game. Results: The WR-0, WR-5, and WR-10 groups exhibited significantly higher RPE values post-WR warm-up than the control group (p = 0.02). At the 5th min of the game, the WR-5 and WR-10 groups reported significantly higher RPE values than the WR-0 and control groups (p = 0.001). Regarding sprint performance, the control and WR-0 groups recorded higher sprint times than the WR-5 and WR-10 groups at both the 5th min (p = 0.049) and the 45th min (p = 0.04) of play. Conclusions: Preconditioning with a 5–10% body mass WR effectively enhances sprint performance in adolescent soccer players. Furthermore, incorporating a WR warm-up routine can optimise sprint performance without overloading adolescent athletes during training sessions.

Background: Early childhood represents a key stage for the development of movement behaviors (MB), motor skills (MS), and executive functions (EF). Body Mass Index (BMI), defined according to World Health Organization (WHO) references, may influence these domains early in life. In this context, this cross-sectional observational study aimed to examine the associations between BMI and 24-h MB, MS, and EF in Tunisian preschool children aged 4 to 5 years. Methods: This cross-sectional observational study included 112 Tunisian children aged 4 to 5 years (50 boys, 62 girls), recruited from kindergartens in urban and rural areas. Anthropometric measurements were used to calculate age-specific BMI z-scores and classify children into three BMI categories: below normal, normal, and above normal. Twenty-four-hour MB physical activity (PA), sedentary behavior (SB), and sleep were objectively assessed using accelerometry over five consecutive days. EF (inhibition and working memory) were assessed using standardized cognitive tests, gross MS were evaluated using the Supine Timed Up and Go test (functional mobility), One-Leg Standing Balance test (postural steadiness), Hand Grip Dynamometer (upper body strength), and Standing Long Jump (lower body strength), and fine MS were assessed using the 9-Hole Pegboard Test (dexterity). All tools are validated and standardized for children. Results: Significant differences between BMI categories were observed for anthropometric variables (p < 0.05). In contrast, no significant differences were found for 24-h MB, adherence to recommendations, EF, and MS (p > 0.05). Only Sleep duration showed a difference significantly between BMI < normal and BMI > normal (p = 0.022). Conclusions: In Tunisian preschool children, weight status is primarily associated with differences in physical growth, with no marked relationship to MB, EF, or MS. These findings highlight the importance of universal preventive interventions, particularly focusing on growth monitoring, starting in early childhood. These results should be interpreted with caution and highlight the need for further studies on larger populations to better understand the relationships between BMI, PA, and development in young children.

Background: Early childhood represents a key stage for the development of movement behaviors (MV), motor skills (MS), and executive functions (EF). Body Mass Index (BMI), defined according to World Health Organization (WHO) references, may influence these domains early in life. In this context, this cross-sectional observational study aimed to examine the associations between BMI and 24-hour MV, MS, and EF in Tunisian preschool children aged 4 to 5 years. Methods: This cross-sectional observational study included 112 Tunisian children aged 4 to 5 years (50 boys, 62 girls), recruited from kindergartens in urban and rural areas. Anthropometric measurements were used to calculate age-specific BMI z-scores and classify children into three BMI categories: below normal, normal, and above normal. 24-hour MV (physical activity (PA), sedentary behavior, and sleep) were objectively assessed using accelerometry over five consecutive days. EF (inhibition and working memory) were assessed using standardized cognitive tests, gross MS were evaluated using the Supine Timed Up and Go test (functional mobility), One-Leg Standing Balance test (postural steadiness), Hand Grip Dynamometer (upper body strength), and Standing Long Jump (lower body strength), and fine MS were assessed using the 9-Hole Pegboard Test (dexterity). All tools are validated and standardized for children. Results: Significant differences between BMI categories were observed for anthropometric variables (p < 0.05). In contrast, no significant differences were found for 24-hour MV, adherence to recommendations, EF, or most MS (p > 0.05). Only upper limb strength showed a significant difference (p = 0.035), with children of normal BMI showing slightly higher strength than those with above-normal BMI. Conclusion: In Tunisian preschool children, weight status is primarily associated with differences in physical growth, with no marked relationship to MV, EF, or MS. These findings highlight the importance of universal preventive interventions starting in early childhood.

Background: Early childhood and education centres (ECECs) are key settings in the promotion of healthy levels of outdoor play and napping among young children. Aim: This study aimed to examine the associations between environmental factors and preschoolers' outdoor play and napping in ECECs across an international sample. Methods: Data from 187 ECECs in 27 countries (22 low‐ and middle–income countries) that participated in the third pilot phase (January 2021–April 2025) of the SUNRISE International Study were analysed. The director of each ECEC completed a questionnaire which asked if children participating in the SUNRISE Study were unable to participate in outdoor play and nap time due to a range of environmental barriers. Results: Forty‐six percent ( n = 86) of ECECs reported at least one environmental factor that prevented preschoolers' outdoor play, and 20% ( n = 37) reported at least one factor that disrupted naptime. Hot and cold temperatures, rain and other factors were observed as barriers to outdoor play across regions and country income levels. Indoor noise, extreme temperatures, brightness and lack of space were reported as disrupting preschoolers' naptime across regions and country income levels. For rural ECECs, hot temperatures and lack of space were barriers for outdoor play and napping, respectively. Conclusions: Context‐specific strategies are required to create climate‐resilient outdoor play spaces and more restful napping environments to optimise early childhood development within ECECs.

To examine the associations between parent perceived environmental factors, nighttime sleep duration and 24-h sleep duration among an international sample of preschool-aged children. Secondary analyses of cross-sectional data from preschoolers across 23 countries (19 LMICs), collected during the third pilot phase (January 2021-August 2024) of the SUNRISE Study. Parents completed a questionnaire which asked about their child's sleep patterns and environmental factors that impacted their child's sleep in the previous 3 days. Data from 2,219 children were analyzed. A significant difference was observed between nighttime sleep (F = 14.27, p = p = 0.0004) across country income level. Environmental factors such as heat (-12.87, 95% CI: -11.54, -0.61) and cold (-17.70, 95% CI: -34.53, -0.85) were negatively associated with nighttime sleep duration. Public health researchers and professionals should prioritize context-specific strategies to minimize the impact of weather conditions on sleep to promote healthy levels of sleep among preschoolers from diverse settings.

Background: Early childhood is crucial for motor and cognitive development, with physical activity playing a key role. Mini-trampoline exercises may offer an effective approach to enhance these domains. Methods: This study assessed the effects of a mini-trampoline program on executive functions and motor skills in Tunisian preschoolers. Fifty-four children (age 3.87 ± 0.47 years) participated in a 12-week intervention, divided into a control group (n = 27), following standard activities, and an experimental group (n = 27), engaging in mini-trampoline exercises. Pre- and post-tests measured motor skills like postural steadiness, balance, and coordination, as well as cognitive functions, including working memory (WM) and inhibition. Results: Significant improvements were observed in the experimental group for functional mobility, postural steadiness, lower body strength, and inhibition (p < 0.001), whereas the control group showed minimal changes. ANOVA revealed no significant group × time effects, except for a trend in postural steadiness (p = 0.062), suggesting a potential benefit of the intervention. Conclusions: These findings highlight the potential of mini-trampoline exercises to enhance motor skills and specific executive functions in preschoolers, supporting their overall development.