Impact of Exhaustive Run on the Lower Extremity Biomechanics

Purpose: The aim of this study was to investigate kinematic and kinetic changes occurred in stance phase during running to exhaustion.

Methods: 8 male recreational runners (age 22.5±1.6 years old, height 177.60±0.02cm and mass 80.6±8.63kg) from local community were participants in this study. They had no lower extremity injury history within-six months, and in apparent good health. AMTI three dimensional force treadmill was used to measure the ground reaction force, and the speed were set at 7.5 mile/hour with sample frequency of 1000Hz. Vicon Motion system with 8 cameras was used for capturing 3D kinematic movements of lower extremities with 40 14mm reflective markers. The sampling frequency was set at 200Hz. The participants were instructed to run on the treadmill until they cannot run, due to exhaustion, anymore. Ten seconds he data of from the start, middle and end of the run were calculated and processed by using C-Motion visual 3D software for both kinetics and kinematics parameters.

Results: Stride duration decreased (0.72±0.03 vs. 0.71±0.04s, at the start and end of the run, respectively), and stance phase duration increased (0.23±0.01 vs and 0.23±0.01s) as observed in this study. More ankle plantarflexion (-44.9±5.4 vs -46.4±5.5°) was noted at foot contact during run to exhaustion. No prominent adjustment of knee flexion (46.2±4.3 vs. 45.2±7.0°) was observed during foot initial contact, but an increase (12.2±4.2 vs. 10.2±3.8°) observed during toe-off. There was a decline of ankle plantarflexion moment (3.2±0.3 vs. 3.1±0.3 N-m/kg) and an increase of knee extension moment (2.8±0.4 vs. 3.0±0.7 N-m/kg) observed.

Conclusion: There was a trend of adjustment of sagittal plane kinematics and kinetics variables observed., regarded as runners were seeking to modulate movements for protecting themselves from injury potential.