An Investigation of Factors Affecting Dynamic Postural Stability in Collegiate Cross Country Runners

Abstract

Injury rates for NCAA cross country runners between 2009 and 2014 were 4.7-5.9/1000 athlete exposures. Prevalence of running-related injuries in the general population has been shown to be between 18-92%. Injury could lead to impaired balance which is a common aspect of return-to-sport rehabilitation programs, and various methods of its assessment have been proposed. The Dynamic Postural Stability Index (DPSI) was introduced to measure variability in tri-axial ground reaction forces during specific tasks. DPSI has been shown to be increased in injured runners and predict athletic performance in soccer players. DPSI has been correlated to ankle range of motion and strength in military personnel. These variables have not been measured in healthy collegiate runners. PURPOSE: To investigate how previous injury affects DPSI and explore relationship between ankle range of motion and strength with DPSI in collegiate runners. METHODS: Twenty-seven Division I collegiate cross country athletes (age: 19.8±1.3 years) participated. Those with an injury in the past 3 years were categorized in the injured group (IG). Athletes jumped over a hurdle on to a force plate and landed on a single leg. Three trials were performed on each leg. DPSI was calculated for the first 3s after landing. Ankle range of motion was assessed via active dorsiflexion and gastrocnemius length measurement. Ankle and hip strength were measured using a handheld dynamometer. An independent samples t-test was used to determine differences in DPSI between IG and uninjured group (UG). Pearson’s correlation coefficient was used to determine relationships between DPSI and other variables. RESULTS: No significant difference was found for DPSI on left (IG: 0.30±0.03 vs. UG: 0.32±0.04) and right (IG: 0.30± 0.03 vs. UG: 0.31±0.03) sides. There was a significant moderate negative correlation between dorsiflexion range of motion and DPSI (right side r= -0.605, p= 0.001; left side r= -0.452, p= 0.001). There were no correlations between strength and DPSI except for right inversion strength and right DPSI (r= 0.446, p=0.020). CONCLUSION: DPSI seems to be influenced to a greater extent by ankle dorsiflexion than strength or previous injury in a collegiate running population; therefore, improving ankle dorsiflexion may be used as a rehabilitation strategy to improve DPSI.