SYNERGYFIELD: Cerebral and Autonomic Coherence in Team Play Evaluation and Training of EEG and HRV Synchronization Between Teammates for the Optimization of Collective Performance

Modern elite team sport requires more than the aggregation of individual physical and technical capacities; it demands rapid, nonverbal coordination and shared decision-making under pressure. Emerging evidence from social neuroscience suggests that such collective efficiency may be grounded in measurable neurophysiological synchronization between interacting individuals. The SYNERGYFIELD study investigated whether inter-brain EEG coherence and interpersonal heart rate variability (HRV) alignment between teammates can be systematically measured and enhanced through a structured multimodal intervention. In a randomized, controlled, longitudinal design, 24 elite athletes (12 tactical dyads) were assigned to either an experimental group receiving six sessions of integrated hyperscanning EEG, synchronized neurofeedback (Alpha–SMR), paired HRV biofeedback, transcutaneous vagus nerve stimulation (tVNS), binaural auditory entrainment, and photobiomodulation, or to a control group undergoing tactical simulations without physiological feedback. Pre- and post-intervention assessments included inter-brain EEG synchronization indices, interpersonal HRV coherence, neurofeedback convergence metrics, Group Environment Questionnaire (GEQ) scores, and structured coach ratings. Results demonstrated significantly higher EEG synchronization (0.84 vs. 0.52), greater HRV coherence (0.46 vs. 0.22), faster SMR convergence, and substantial improvements in perceived and externally observed cohesion in the experimental group. These findings suggest that neural and autonomic coherence within tactical dyads is modifiable and functionally associated with improved collective coordination. SYNERGYFIELD introduces a translational framework for relational neurotraining in elite sport, reframing team performance as a dynamic neurophysiological network process rather than solely a tactical construct.