Significantly and practically meaningful differences in balance research: P values and/or effect sizes?

Abstract

This paper examines statistical and practical significance when interpreting outcomes of balance research studies. The analysis has been restricted to studies differing in groups of interest and types of balance training; however, using equal parameters of task-oriented balance tests. While large samples differed significantly, no significant differences were found between small groups of athletes of different specializations. Likewise, the values did not differ significantly during stance on injured and non-injured legs. Nevertheless, moderate to large effect sizes indicate that the data are particularly meaningful in terms of sport and rehabilitation practice. On the contrary, visual feedback balance training in school-age children showed highly statistically significant changes, though the effects were trivial. Some discrepancy was also found between statistically significant changes after balance training in untrained subjects and small to high effect sizes. However, statistical significance of different balance training programs in physically active individuals and competitive athletes corresponded with calculated effect sizes. These findings signify that frequently used statistical significance in balance research does not imply that changes observed after the training are practically meaningful, or vice versa. Therefore, both P values and effect sizes should be used when interpreting results of cross-sectional and intervention balance studies.