Comparison and correlation of dynamic postural stability indices obtained during different dynamic landing tasks and footwear conditions

Introduction: Dynamic postural stability is a commonly studied risk factor for lower-extremity injury. Single leg jump-landings (SLJL) and the dynamic postural stability index (DPSI) are widely used methods for testing and calculating dynamic postural stability. Two different SLJL protocols are often used to calculate DPSI scores throughout the literature: one is based on normalized jump distance (NDP) and the other is based on normalized jump height (RWDP), with or without shoes. Given the prevalence of these protocols, it is important to compare DPSI scores during the two different SLJL measures while examining the effect of footwear. Methods: Subjects (n=25) completed the two SLJL protocols shod and barefoot. Both protocols required subjects to jump-off two feet and land with their dominant foot on a force-plate. Based on normality, paired t-tests or Wilcoxon signed-rank tests and Pearson or Spearman correlation coefficient were used to compare and measure the relationship between the two protocols under two footwear conditions (p<0.05). Results: The NDP and RWDP were not significantly different from each other in either footwear condition (p=0.233; 0.654). The two protocols were significantly correlated under the barefoot condition (r=0.565; p=0.003), but not under the shod condition (r=0.382, p=0.060). NDP scores under the shod and barefoot conditions were significantly different (p<0.001) but correlated (r=0.870, p<0.001). RWDP scores under the shod and barefoot conditions were not significantly different (p=0.090) and correlated (r=0.786, p<0.001). Conclusion: Different protocols and footwear conditions may impact DPSI scores. Therefore, a standardized protocol and footwear condition should be established for future studies.