EFFECTS OF A STRENUOUS ECCENTRIC KNEE EXTENSORS EXERCISE ON THREE DIMENSIONAL RUNNING BIOMECHANICS AND PHYSIOLOGIC PARAMETERS DURING AN EXHAUSTIVE ENDURANCE TEST.

INTRODUCTION:
The occurrence of exercise-induced muscle damage (EIMD) can affect the running pattern and endurance performance. However, the EIMD-induced changes in biomechanical and physiologic parameters remain poorly understood. The aim of this study was to examine the effects of a single isokinetic eccentric (ECC) exercise and ensuing DOMS on running biomechanics, physiologic measures and muscle activity during an endurance exercise performed 48h later.
METHODS:
Twelve healthy , moderately active adult men completed two treadmill running tests (at 85% Maximal aerobic speed) until exhaustion, with a week interval between both tests. Participants were submitted to a bilateral isokinetic eccentric protocol on the knee extensors 48hours before the second test. The subject’s running kinematics (using a 3D motion system), heart rate, ventilation, pulmonary gas exchange and muscle activity were continuously recorded during the running tests. Delayed-Onset Muscle Soreness, plasma creatine kinase, muscle extensibility, muscle function were assessed before and 48h after the ECC exercise.

RESULTS:
In presence of EIMD, the running time to exhaustion was shorter (p<0.05) while the Borg rate of perceived exertion was higher (p<0.01). Muscle force and vertical jump performance were also reduced with EIMD. The physiological data showed no significant difference between both endurance tests, except for the lactate level and heart rate measured at the end of the test which appeared significantly higher with EIMD (p<0.05). In contrast, the 3D analysis revealed a significant decrease in stride length and a significant increase in stride frequency and stance phase with DOMS. Articular amplitudes and electromyography data showed no significant change although some trends are noteworthy, such as increased muscle activity.

CONCLUSION:
Our data suggest that the presence of knee extensors EIMD altered the running biomechanics and endurance performance without significative changes of the physiological parameters. Further investigations are required to explore whether the EIMD-induced biomechanical modifications are the result of pain perception or impaired muscle function.