Verification of Relationship between Static and Dynamic Balance Using Cross Test Trajectory Diagram as Indicator

Purpose: The aim of this study was to clarify the relationship between static and dynamic balance using the cross-test trajectory diagram as an index. Method: The participants were 14 male trampoline gymnasts. Center-of-gravity sway meter was used to measure balance ability. Static balance was recorded in the following conditions: mandibular resting position (RP), intercuspal position (Cl), and mouthguard worn (MG-Cl), and the outer circumferential area (ENV-area) and unit area trajectory length (LNG/E-area) were recorded. Dynamic balance was evaluated using the R/E-value calculated by the cross-test. In addition to static balance, two conditions were measured without clenching instructions: without mouthguard (Fr) and with mouthguard (MG-Fr). Differences in ENV-area or LNG/E-area due to occlusal conditions were analyzed using the Friedmann test. Differences in the R/E value due to occlusal conditions were compared using repeated measures analysis of variance. Correlation analyses between static and dynamic balance were performed in RP, Cl, and MG-Cl using Pearson’s product moment correlation coefficient or Spearman’s rank correlation coefficient. Results: For MG-Cl, ENV-area had the lowest value, while LNG/E-area and R/E-value were the highest. In RP or MG-Cl, a negative correlation was observed between ENV-area and R/E-value and a positive correlation between LNG/E-area and R/E-value (P < 0.05). Conclusion: This study clarified that the relationship between static and dynamic balance was observed in mandibular resting position and mouthguard worn. Therefore, the R/E-value reflects static balance, suggesting that the center of gravity can be moved efficiently in an internal environment with stable static balance.