Extended Abstract
Background and Purpose
In the present era, achieving optimal performance in team and competitive sports requires, in addition to physical factors, the cognitive and psychological abilities of athletes. One of these key abilities is cognitive flexibility, which means the individual's capacity to adapt to new internal and external experiences, change thinking, and respond appropriately to challenges and environmental changes. This characteristic allows athletes to adapt their decision-making strategies, invent new solutions, and rebuild their cognitive structures in dynamic and unpredictable environments. In sports such as volleyball, which require rapid reactions and instantaneous decision-making, cognitive flexibility is a critical factor for success. Based on cognitive psychology theories and the principles of ecological dynamics, it seems that placing athletes in diverse and dynamic training environments can, as an effective training intervention, improve cognitive flexibility and, consequently, sports performance. In this approach, instead of constant repetition of skills, by manipulating the constraints of the task (e.g. rules, number of players, time) and the environment (e.g. type of field, light, equipment), the athlete is forced to actively search for adaptive motor solutions. This process not only leads to deeper motor learning, but also strengthens the cognitive capacity of the individual to process variable information and make quick decisions.
Despite theoretical evidence and limited studies in some sports (e.g. soccer and futsal) that emphasize the positive effect of varied training on creativity and some performance aspects, there was a clear research gap in simultaneously examining the effect of these exercises on cognitive flexibility and skill performance in volleyball, and especially among adolescent female athletes. Therefore, the main aim of this study was to determine the effect of a training intervention based on a varied environment on improving cognitive flexibility and performance of toe and serve skills in adolescent female volleyball players.
Methods
This study was a quasi-experimental study with a pre-test and post-test design and a control group. The statistical population consisted of teenage female volleyball players (14 to 18 years old) from professional clubs in Tehran. Using G*Power software and considering an effect size of 0.25, an alpha level of 0.05, and a power of 0.95, a sample size of 60 was determined. These individuals were randomly assigned to two groups of 30: the experimental group (training in a diverse environment) and the control group (training in a non-diverse/standard environment). Participants were classified as trained/developing athletes. The experimental group trained in a diverse environment for five weeks and ten training sessions in which variables such as the court surface (e.g. changing the flooring), the type of ball (balls of different weights or sizes), lighting conditions, the number of players on the court, and the rules of the game were constantly changing. This design was based on the principles of ecological dynamics and aimed to create diverse perceptual-motor challenges. In contrast, the control group performed the same volleyball exercises but exclusively in a standard and constant environment (standard 6x6 court, standard ball, constant light). Two main tools were used to collect data: Dennis and Vander Wal's (2010) Cognitive Flexibility Questionnaire (CFI): This 20-item questionnaire with a 7-point Likert scale provided an overall score of individuals' cognitive flexibility. AAHPERD volleyball Skills Test: To objectively assess performance, the service and overhead set-to-wall test were used. In the pre-test, post-test (immediately after the intervention), retention test (24 hours later), and transfer test (72 hours later under similar but not exactly identical conditions), each player performed 10 service attempts and 10 toe attempts and the scores were recorded. Data were analyzed using SPSS version 26. For cognitive flexibility, analysis of covariance (ANCOVA) was used to compare post-test scores between the two groups while controlling for pre-test scores. For service and overhead set-to-wall performance, a mixed two-way ANOVA with a 2 (group: diverse-environment training, non-diverse-environment training) × 4 (time: pre-test, post-test, retention, and transfer) design was used. When significant differences were observed, Bonferroni-adjusted pairwise comparisons were performed. The significance level was set at 0.05, and partial eta squared (η²p) was reported as the effect size.
Results
The research findings clearly indicated a positive and significant effect of practicing in a diverse environment: In the case of cognitive flexibility, the results showed that there was a significant difference between the two groups after the intervention (p < 0.001). The experimental group showed a significant increase in the cognitive flexibility score at the post-test compared to the control group (p < 0.001, d = 2.19). In the case of skill performance, for both the toe (p < 0.001, η²p = 0.186, F = 13.21) and the serve (p < 0.001, η²p = 0.204, F = 14.89), a significant interaction of group and time was observed. In other words, the improvement in performance in the experimental group at the post-test, retention, and transfer stages was significantly greater than that of the control group.
Conclusion
These results confirm that training in diverse and dynamic environments not only sustainably improves (maintains and transfers) physical and skill performance (swing and serve) of adolescent female volleyball players, but also simultaneously enhances their cognitive flexibility. In conclusion, this study provides strong evidence that training in a diverse environment, as a new training approach rooted in ecological dynamics and cognitive science, is an effective tool for simultaneously improving technical performance and cognitive flexibility in team athletes. The findings of this study not only fill the existing research gap, but also have important practical implications for volleyball coaches and sport psychologists. It is suggested that coaches, by departing from traditional and static training frameworks, incorporate variety and change as a key element in the design of their training sessions through conscious planning. Integrating such protocols into standard training routines can better prepare athletes for the unpredictable challenges of competition and help improve the quality of team performance and achieve higher levels of competition.

Article Message
The findings are consistent with the ecological dynamics approach and indicate that training in a diverse environment simultaneously improves cognitive flexibility and performance through increased cognitive load and perception-action couplings. This novel approach is suggested to be included as a standard protocol in team sports coaching.
Ethical Considerations
Before implementing this study, the proposal for this work was reviewed and approved by the Specialized Committee on Sports Sciences of Ivanki University, and permission to implement it was issued. The ethics code for this study was obtained from Damghan University with code IR.DU.REC.1404.003.
Authors' Contributions
Conceptualization: Behzad Mohammadi Orangi, Data Collection: Sahar Nasrollahzadeh, Data Analysis: Behzad Mohammadi Orangi, Manuscript Writing: Behzad Mohammadi Orangi, Leily Alizadeh, Review and Editing: Behzad Mohammadi Orangi, Leily Alizadeh, Responsible for funding: No funding, Literature Review: Behzad Mohammadi Orangi, Leily Alizadeh, Project Manager: Behzad Mohammadi Orangi, Any other Contributions: No other contributions
Conflict of Interest
The author(s) declare that there is no conflict of interest regarding the publication of this article.
Acknowledgments
The author(s) would like to express their sincere gratitude to the participants who made this study possible.