For this project, all study procedures were conducted in accordance with protocols approved by the Fakultní Nemocnice Brno (Brno, Czech Republic; 14-110123/EK). Participant assent and parental consent were obtained prior to study participation in person by the study team. All study data were deidentified to ensure privacy and confidentiality protections were in place. No compensation was given for participating in this study.

A total of 59 tennis players (age: mean 16.7, SD 3.6 years; 34 male) from the Czech Lawn Tenis Klub (Prague, Czech Republic) were invited to participate in this study (and provided a full overview of the study procedures and time requirements). See Multimedia Appendix 1 for more details.

The Mastermind Cognitive Training program used a virtual reality (VR) headset (Oculus Quest 2 by Meta) to deliver a custom cognitive training program targeting specific cognitive control abilities including attention, working memory, and goal management. The VR component comprised 3 modules, each focusing on a different aspect of cognitive control: a multiple object–tracking module aimed at engaging attention (with increasing distraction), a spatial span module to engage working memory, and a visual search module with task switching requirements to engage multitasking abilities. In each case, participants used VR hand-held controllers (Figure 1A) to respond to stimuli presented in a video game–like environment, in some cases “shooting” specific target stimuli while avoiding others (Figure 1B), or trying to catch certain colored targets in a given order stimuli while avoiding nontargets (Figure 1C). Each module was adaptive, adjusting task difficulty based on performance. In addition, participants completed 20 minutes of tablet-based training (iPad) on tasks related to rhythmic timing (where participants were asked to tap on the screen to the beat of music being played [28-31]; Figure 1D). The intervention group was asked to complete 24 program sessions over the course of 10 weeks, with each session consisting of 15 minutes of VR exercises and 20 minutes of tablet-based exercises, totaling approximately 14 hours of training. See Multimedia Appendix 1 for more details.

The primary outcome measure was the change in Universal Tennis Rating (UTR), a scale from 1.00 (eg, a beginner player) to 16.50 (eg, a professional player; for context, the current #1 player in the world is rated 16.05), which promotes fair and competitive play [32]. Each player’s UTR was collected before training and after the completion of the 24-session training period, which an interassessment interval of approximately 4 months. See Multimedia Appendix 1 for more details about this measure.

The primary goal of this proof-of-concept pilot study was to investigate the effects of the Mastermind Cognitive Training program in adolescent tennis players. These findings suggest that supplementing regular training with cognitive training can lead to meaningful improvements in real-world athletic performance. It has been suggested that visual-based training (including the use of VR and/or tablet platforms) is more likely to benefit trained athletes than novices [35]. Indeed, this theory has empirical support: “real-world” improvements have been observed, including performance in college-level baseball players [36,37] as well as table tennis performance [38] when coupling such training with their regular sports training [38]. In conjunction with those studies, the present findings suggest that training cognitive abilities through an immersive visual platform may benefit performance on athletic endeavors, including tennis. Such a result warrants careful consideration, given the known difficulties in evidencing far transfer not just in cognitive studies, but especially in athletic activities [7]. That said, our findings do align with those of the few positive studies demonstrating that cognitive training can result in some form of on-field improvements [8,9]. See Multimedia Appendix 1 for a further discussion of practical considerations.

Several limitations should be considered with the present findings. First, the most important factor to consider with this study is the small sample size, especially considering the large number of individuals who did not complete the study. It should be noted that this study was not designed to be anything more than a pilot study intended to gauge the feasibility of implementing the Mastermind Cognitive Training program following the unexpected opportunity to work with adolescent tennis players. Future work must involve a larger trial of participants to replicate these findings to provide supporting evidence for the present interpretations. Second, the very real possibility exists that participation in the intervention generated a placebo effect through the novel use of a VR platform. Given the pervasive problem of placebo effects in such work [39], it is critical that future endeavors account for these effects in a carefully designed manner. Finally, it is unknown what aspect of the training program led to the improvement in UTR. The absence of cognitive control outcome measures to assess whether, and to what extent, this training program led to cognitive changes hinders a deeper understanding of what possibly drove the differential improvement in UTR. Future work is warranted to better understand the potential underlying mechanisms driving such change.

This exploratory proof-of-concept study investigated the potential benefits of a novel cognitive intervention platform in a sample of healthy adolescent tennis athletes. It represents the first step toward a number of data-driven studies demonstrating the utility and benefits of the use of this platform. These pilot findings suggest that this platform may be beneficial for adolescent tennis athletes looking to improve their sporting performance by supplementing their existing training protocols with a targeted cognitive training experience. However, many questions remain unanswered, and further work is needed to better understand the potential utility and mechanisms underlying potential effects of such a platform.