The purpose of this study was to clarify factors that affect the tension of pitchers during competition. We calculated heart rate change (HRc; the degree of tension) by measuring the heart rates of eight pitchers under both practice and competitive conditions. In analysis 1, we performed a multiple regression analysis using competitive situation factors (1. the number of balls; 2. the number of strikes; 3. the number of outs; 4. the presence or absence of a runner in a scoring position and 5. the score difference) and cognitive appraisal factors (6. subjective degree of tension and 7. subjective winning percentages) as independent variables, and HRc as the dependent variable. In analysis 2, we reconstructed analysis 1 to add a factor related to individual difference. Our results showed that the factors that can affect HRc were subjective winning percentages, subjective degree of tension, and the number of balls. Moreover, the accuracy of the model was improved by adding a factor related to individual differences (R2＝0.13－0.47). The differences in pitching stats among participants were considered as individual differences in this study.
