Group Cohesion and Salivary Oxytocin During a Six-Month Coordination-Based Training Program in Junior Handball Players: A Prospective Non-Randomized Controlled Intervention Study

Background/Objectives: Whether coordination-based training can develop group cohesion in youth sport, and how cohesion relates to peripheral oxytocin, is unclear. We examined cohesion and salivary oxytocin during a six-month coordination- and cohesion-oriented program in junior handball players. Methods: Sixty-four male players (12–14 years) from four clubs joined a prospective, non-randomized, within-club controlled study (not prospectively registered). In each club, one pre-existing training slot (eight players) formed the experimental group (EG; n = 32) and the other the control group (CG; n = 32). For 24 weeks (three sessions/week), EG replaced 20–25 min of technical–tactical work with coordination, cooperation, and interpersonal-synchrony exercises. The primary outcome was Youth Sport Environment Questionnaire (YSEQ) Task Cohesion. Results: In the baseline-adjusted, cluster-robust analysis, T1 Task Cohesion was 0.72 points higher in EG than CG (95% CI 0.22–1.23; p = 0.010); Social Cohesion differed similarly (adjusted difference 0.77 points; 95% CI 0.33–1.22; p = 0.003). The adjusted oxytocin difference was imprecise and non-significant (5.0 pg/mL; 95% CI −0.01 to 10.02; p = 0.050), and oxytocin change was unrelated to Task Cohesion change. Conclusions: The program was accompanied by a more favorable cohesion trajectory than time-matched standard training. Non-randomized allocation precludes causal conclusions; oxytocin findings remain exploratory.