Vertical jumping is a fundamental motor skill that develops rapidly in early childhood, yet the biomechanical contribution of arm swing in preschool-aged children remains unclear. This study aimed to investigate how arm swing influences countermovement jump (CMJ) performance in typically developing children aged 3 to 6 years. A total of 411 children (53.5% girls; mean age: 4.9 ± 1.1 years) from four European cities participated in this cross-sectional study. Each child completed five CMJs with and without arm swing using the Optojump system, measuring variables such as jump height, flight time, contact time, power, the reactive strength index (RSI), pace, and verticality. The results revealed a significant increase in jump height when using arm swing for both boys (+15%) and girls (+12.5%) (p < 0.001), yet power output, the RSI, pace, and verticality decreased significantly (p < 0.05). These findings suggest that preschool children are not yet biomechanically efficient in integrating arm movements into vertical jumping due to immature neuromuscular coordination. Although arm swing improves jump height, it does not enhance overall movement efficiency at this developmental stage. This study highlights the need for multidimensional and age-appropriate assessment protocols to better understand motor integration during early childhood.

Background/Objectives: Vertical jump is considered a reliable and valid method of assessing the level of muscular power and coordination across one’s lifespan. The main aim of the present study was to establish sex- and age-normative data for vertical jump outcomes in pre-school children. Methods: We recruited 411 boys and girls aged 3−6 years from four major cities in Croatia and Slovenia. Vertical jump was assessed with two tests: countermovement jump (CMJ) without and with arm swing using a reliable and valid Optojump measuring platform. Data were presented for the 5th, 15th, 25th, 50th (median), 75th, 90th, and 95th percentile. Results: No significant differences were observed in multiple vertical jump outcomes between boys and girls. The mean values for CMJ without and with arm swing between boys and girls were as follows: contact time (1.4 vs. 1.4 s/1.8 vs. 1.7 s), flight time (0.32 vs. 0.31 s/0.33 vs. 0.32), height (12.3 vs. 12.2 cm/13.0 vs. 12.5 cm), power (9.4 vs. 9.5 W/kg/9.3 vs. 9.1 W/kg), pace (0.7 vs. 0.7 steps/s/0.6 vs. 0.6 steps/s), reactive strength index (RSI; 0.10 vs. 0.09 m/s/0.08 vs. 0.08 m/s), and verticality (2.5 vs. 2.3/1.9 vs. 1.9). A gradual increase in all measures according to ‘age’ was observed (p for trend < 0.05). No significant ‘sex*age’ interaction was observed (p > 0.05). Conclusions: This is one of the first studies to provide sex- and age-normative data for complete vertical jump outcomes in pre-school children. These data will serve as an avenue for monitoring and tracking motor development in this sensitive period.

Although it has been confirmed that overweight and obesity may have negative impact on jumping performance in school-aged children and adolescents, little evidence has been provided for pre-school children. The findings have provided inconclusive results, but mostly that overweight and obese pre-school children do not have an impaired jumping performance, in comparison to their normal weight peers. Therefore, the main purpose of the study was to examine the differences between normal weight and overweight/obese pre-school children in jumping performance outcomes and their correlations with anthropometric indices. Four-hundred and eleven pre-school children with the mean (SD) age = 4.9 (1.1) years, height = 111.2 (9.3) cm, weight = 20.0 (4.2) kg, 53.5% girls were recruited from 34 kindergartens in four major cities. Anthropometric indices included body mass index (BMI), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). Normal weight, overweight and obesity were classified according to international norms. Jumping performance was evaluated by the countermovement jump (CMJ) without and with arm swing with Optojump system. In general, pre-school children with overweight and obesity exhibited poorer performance in vertical jumping; they had shorter flight time and flight height, lower power relative to body mass and lower relative strength index (RSI), compared to normal weight children. The strongest correlations were observed between WHtR and jumping outcomes, where higher WHtR values led to shorter flight time and flight height, and lower power relative to body mass in both boys and girls. This study adds new information related to nutritional status and jumping performance in pre-school children. Thus, overweight and obesity need to be considered, when monitoring vertical jumping performance.

Background/Objectives: Running is among the most prevalent forms of physical activity in preschool-aged children and constitutes a fundamental component for the effective execution of other motor patterns. The main aim of this study is to determine how fundamental running parameters change with age and whether there are differences between sexes. Methods: Four-hundred and five pre-school children with the mean (SD) age = 4.9 (1.1) years, height = 111.2 (9.3) cm, weight = 20.0 (4.2) kg, 53.5% girls were recruited from 34 kindergartens in four major cities. The inclusion criteria involved children aged 3–6 years with typical development and without any locomotor or mental disorders and diseases, who were enrolled in day care. Running performance was assessed in preschool children using a 10-m sprint test. Sprint parameters were measured with the OptoJump modular system, an infrared platform that accurately quantifies kinematic variables. Sex (boys vs. girls) and age (3 to 6 years old) differences were calculated by using analysis of variance (ANOVA) or Kruskal–Wallis H-test with post hoc comparison test between the groups. Results: In general, the results indicated that statistically significant differences between boys and girls were observed across the following levels: (1) temporal–kinematic step phase, (2) spatiotemporal movement characteristics, and (3) propulsive phase as an indicator of muscular activity. However, these differences were not consistent across all age groups. Conclusions: This study provides new insights into the spatiotemporal characteristics of running in preschool-aged children. The findings may assist in the early identification of potential motor deviations and in the planning of more effective strategies to promote physical activity during the preschool period.