Assessing Asymmetry In Collegiate Sprint And Intermediate Hurdlers

Asymmetric limb movements are a commonly studied phenomena in athletics despite the ambiguous nature of their effects on both performance and injury risk. Sports involving discrete movements with a dominant limb such as baseball and tennis have high levels of side-to-side asymmetry. In addition, asymmetries are also present in cyclic movements involving locomotion such as sprinting and distance running. Asymmetries in hurdling, an asymmetric type of sprinting with lead and trail legs, have yet to be thoroughly examined. PURPOSE: The purpose of this study was to examine lead and trail leg asymmetries in hurdlers during a countermovement jump (CMJ). METHODS: Nine hurdlers (7 M, 2 F; age: 21.4 ± 3.1 years, height: 179.3 ± 6.9 cm, mass: 76.4 ± 7.3 kg) performed a total of five maximal effort CMJs. Dual force plates (HPS400600; AMTI; Watertown, MA, USA) were used to collect kinetic data: propulsive impulse [PI], breaking impulse [BI], propulsive force [PF], peak force [PeF], eccentric rate of force development [eRFD], peak positive power [PPP], and peak negative power [PNP]. Data was collected and analyzed using AccuPower 4.0 software. The symmetry index (SI) and absolute symmetry index (ASI) between the lead and trail legs were determined for all variables. Chi-square goodness of fit tests were used to determine any directional trends (toward the lead or trail leg) or number of athletes above a critical 10% asymmetry injury risk threshold. All athletes were checked for intrapersonal significance between the limbs and for above-threshold asymmetries. RESULTS: There were no significant directional trends for any of the kinetic variables. While there were no variables for which the SI was above the 10% threshold, there were several variables with ASI values above this level: BI (ASI = 12.1 ± 12.9%), eRFD (ASI = 21.7 ± 9.4%), and PNP (ASI = 12.5 ± 10.5%). There were significantly more athletes above the 10% threshold only for eRFD (χ2 = 5.44; p < .05). Every athlete had at least one variable for which they displayed significant intrapersonal asymmetry in their CMJ and an asymmetry above the 10% injury risk threshold. CONCLUSION: Hurdlers display high levels of asymmetry during CMJs but without directional trends based on their lead/trail leg. Despite the asymmetry of hurdling, side-to-side differences are comparable to that of sprinters.