No Relationship between Functional Exercise Assessments and Running Biomechanics in Triathletes

Abstract

Epidemiological evidence suggests that knee overuse injuries are common in triathlon. Aberrant hip biomechanics have recently been implicated in the etiology of chronic knee pathologies. It is possible that prolonged cycling in the aerodynamic position affects hip and knee running biomechanics in triathlon. Excessive hip internal rotation during running stance may place the knee in a position of excessive knee valgus thereby exposing it to excessive external forces that may lead to a chronic knee injury. Using functional screening may provide clinicians an opportunity to identify triathletes at risk for developing biomechanical changes when running. PURPOSE: To determine if average peak angle change to hip and knee running kinematics differs between high and low functional screen scores. METHODS: Healthy subjects with prior triathlon experience (N=28,height=1.73 ± 0.09 m, mass=63.0 ±7.7kg, age =24.6±5.8 years) were used. 3D running kinematics were obtained before and at 4 time points (2min, 6min, 10min, 14min) following a 30-min aerodynamic cycling protocol to obtain average peak angle changes at the hip and knee. The Functional Movement Screen (FMS) and a side-bridge suspension (ST) exercise test were utilized as the functional screens. Average change from baseline for peak hip internal rotation and knee abduction was calculated. Median total scores on the FMS (max possible score of 21) and ST (max of 10) were used to dichotomize subjects into high and low functioning groups. Independent-samples t-tests were used to compare average change between high and low scorers. RESULTS: Median FMS score was 16 and ST score was 4.5. No significant differences were found between low and high performers for changes to Hip IR (FMS<16=4.9°±6.9° vs. FMS>16=5.0°±7.4°,p=.80 ST<4.5=3.2°±6.8° vs. ST>4.5=6.7°±7.1°,p=.93), or Knee ABD (FMS<16=2.1°±3.7° vs. FMS>16=2.1°±4.3°,p=.98 ST<4.5=1.3°±3.4° vs. ST>4.5=2.9°±4.5°,p=.20). CONCLUSION: Cycling significantly alters transverse plane hip and frontal plane knee running biomechanics; however, the changes are not different between high and low scorers on functional screens. Screening may not be useful to clinicians attempting to identify athletes who will experience excessive changes to hip and knee running biomechanics following cycling.