Evaluating the effects of external load, incline and walking speed on iliotibial band strain in wildland firefighters

Abstract

<p>Wildland firefighters (WFF) and military personnel encounter extreme environments and working conditions as part of their occupation. High rates of overuse knee injury have been recorded in both populations, with Iliotibial Band Syndrome (ITBS) being the highest reported overuse injury within the military. However, occupational demands that could contribute to such rates of ITBS have not been evaluated. PURPOSE: To evaluate if the effects of slow walking speed, external load carriage and incline increase strain and strain impulse of the ITB as a predictor of ITBS risk and to update the current ITB model to include the active components of the structure. Current models only include a passive strand but will be updated to represent muscular attachments (ITB_TFL, ITB_GM12, and ITB_GM34). METHODS: Eleven healthy participants from the targeted population completed 10 trials each of three overground walking conditions that varied speed and load (45 lbs) and two ramped (24˚) conditions that varied load. Force plates and infrared motion capture cameras recorded kinetic and kinematic data which was transformed into a rigid body model to calculate reaction forces and joint moments during stance. A musculoskeletal model of the lower extremity calculated maximum muscle forces which were then optimized and used to calculate ITB strain with the added active ITB components. RESULTS: No significant interactions or increases in strain impulse were found. Significant main effects for load and incline were found across all conditions. Increased average peak strain main effects for both load (P<0.001) and incline (P=0.001) were significant in the ITB_TFL strand. The ITB_TFL recorded the largest strain value (11.1%) during the ramped and loaded condition. CONCLUSIONS: Incline and load carriage appear to increase average peak strain values in the active ITB components over normal walking and the updated model provided reasonable estimates of strain compared to strain values reported in the literature. Further research is needed to understand the effect of repeated exposure as a potential determinant of injury.</p>