Factors affecting lower extremity loading during running

Abstract

Objective: The purpose of this study was to systematically alter the knee flexion at contact as runners land from running off of a platform and to document how this angle affects both the impact force and impact acceleration. The platform was used for its similarity to downhill running. Participants: Five male and five female participants volunteered to complete ten trials in each of four conditions. Interventions: Normal running (NR), normal running off a raised platform (NRP), flexed knee running off a raised platform (FRP), and extended knee running off a raised platform (ERP). Main outcome measurements: Kinematic data, ground reaction forces, leg and head acceleration data were collected. Results: Running off a raised platform increased peak impact forces (NR: 1147±171N; NRP: 1826±352N), peak leg accelerations (NR: 7.6±5.3g’s; NRP: 13.9±5.8g’s) and peak head accelerations (NR: 1.4±0.4g’s; NRP: 4.0±1.4g’s). Flexed knee running off the raised platform decreased peak impact forces to 1672±463N but increased peak impact leg accelerations to 16.3±5.7g’s compared to NRP. In contrast, extended knee running off the raised platform increased peak impact forces to 2111±515N but peak leg accelerations did not change 13.5±4.7g’s when compared to NRP. Conclusions: These results suggest that knee flexion decreased the mass that was being accelerated. This decreased mass was easier to accelerate and