This study aimed to examine longitudinal changes in collective cohesion and to explore contributing and contextual factors by conducting a case analysis of a university varsity baseball team over approximately six months, from the offseason in December to the end of the spring season in June. The observation period was divided into four phases: (1) team-organized events period, (2) offseason, (3) preseason games, and (4) official season games. Using the Collective Cohesion Questionnaire in Sport developed by Sugiyama et al. (2021), surveys were conducted 13 times during the study period. The results revealed an overall upward trend in collective cohesion throughout the six months. Notably, experiences of victory during official games significantly contributed to increased cohesion, and team-organized events were also suggested to potentially have a positive influence. In contrast, periods with reduced interaction, such as the offseason, and phases where the team was divided, such as during preseason games, showed stagnation or decline in cohesion. These findings suggest that collective cohesion is a dynamic construct that fluctuates depending on the team's activities and situational context.
