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A cross-sectional design was used. Motion analysis is commonly used to analyze reaching movements of individuals, but how many trials are necessary to provide stable data? The purpose of this study was to determine the number of trials necessary to obtain stable kinematic variables during reaching movements in a virtual environment. Thirty children (10.39 ± 1.68 years) and 20 adults (26.55 ± 3.12 years) participated. All participants interacted with a virtual reality evaluation game called Super Pop VR to collect their reaching kinematics. The players were instructed to pop several sets of virtual bubbles at a self-selected pace and their upper-body coordinates were recorded and reaching kinematics were computed. Two methods (sequential averaging techniques, SAT, and intraclass correlation coefficient, ICC) were carried out to assess performance stability of each kinematic variable. For the SAT method, children exhibited 3.11 to 5.96 trial range to achieve stability in the dominant hand and 2.7 to 5.96 trial range in the nondominant hand, whereas adults exhibited 2.65 to 6.16 trial range in the dominant hand and 3.40 to 6.05 range in the nondominant hand. For the ICC method, to reach the "excellent" value of ICC, children's dominant hand required 4.20 trials and their nondominant hand required 2.5 trials, whereas adults' dominant hand required 3.00 trials and their nondominant hand required 2.80 trials. Our findings supported the importance of determining the minimum number of trials required to obtain stable movements regardless of how familiar the movement seems to participants or how sensitive the apparatus is. • Even when evaluating typical children and healthy adults' reaching movements in a virtual environment, participants still required trial practices to reach performance stability. • The number of trials needed for performance stability was dependent on the methods used. • Reaching in a virtual reality game stabilized after six trials when using the sequential averaging technique, whereas reaching stabilized after five trials in children and after three trials in adults when using the intraclass correlation coefficient method to determine performance stability. [ABSTRACT FROM AUTHOR]