4. Discussion
This study aimed to investigate the effects of plantar flexor stretching on static and dynamic balance in healthy adults. In all stretching groups, ankle joint ROM, balance ability in the eyes-closed condition, and dynamic balance ability improved after the intervention. Differences among stretching types appeared only in sway velocity in the eyes-closed condition; none were seen in other variables. These results suggest that stretching of the ankle plantar flexors can improve balance ability regardless of type.Stretching induces biomechanical and physiological changes within the muscles that can alter muscle activation, strength, and kinesthetic awareness [Several studies, including that of Ryan et al. [Depending on the stretching time, this effect can be observed in several ways. Lewis et al. [Previous studies reported differences in balance ability depending on stretching type. However, our study found no difference according to stretching type. As mentioned above, this is considered due to the application of long-term stretching in this study. Since we applied long-term stretching, the muscle elongation and stimulation reached the anatomical limit regardless of stretching type. As a result, no difference was noted between stretching groups in ankle joint ROM or balance ability.This study confirmed the effect of plantar flexor stretching on balance. However, our study had some limitations. First, because the sample size was small, it is difficult to generalize the study’s results. Second, this study included a limited population. We included only young adults, a high proportion of whom were male. These results may differ for different age groups and gender ratios. Third, the anatomical changes in the muscles and differences in body composition were not evaluated. We indirectly measured muscle changes due to stretching by measuring ankle ROM. As a result, the factors that cause stretching to affect balance other than muscle length and joint angle could not be identified directly. Finally, different stretching times were not applied. The physiological and anatomical effects on the muscles may vary depending on the stretching type and duration. Future studies should analyze changes in balance ability under various intervention conditions.