Muscle fiber conduction velocity of the vastus medilais and lateralis muscle after eccentric exercise induced muscle damage
Oral Presentation XML
1Assistant Professor, University of Bojnord, Bojnord.
2Azad University of Bojnourd
3University of Bojnord
4Assistant Professor of sport biomechanics engineering , Sport Sciences Research Institute Of Iran
Introduction: Vastus medialis (VMO) and vastus lateralis (VL) muscle work synergistically to stabilize the patella during dynamic knee extension. These two muscles are more susceptible to fiber injuries, especially when repetitive lower limb eccentric loading is frequently performed. Due to differences in morphological and architectural characteristics of muscle fibers within the VMO and VL muscle eccentric exercise may result in a non-uniform fiber damage, and as a consequence, non-uniform changes in membrane excitability and conduction velocity. The aim of the study was to investigate MFCV of the VMO and VL muscles before and 24 hours after eccentric exercise.
Methodology: Multichannel surface EMG signals were concurrently recorded from the right VMO and VL muscles of 15 healthy men during sustained isometric contractions at 50% of the maximal force.
Results: Maximal voluntary force significantly reduced after eccentric exercise with respect to the baseline (P<0.0001). MFCV decreased over time during the sustained contractions at faster rates when assessed 24 h after exercise (average for two muscle; 23 ± 8.6% ) with respect to baseline (average for two muscle; 11.4 ± 5.5 % , P<0.00001). Moreover, VMO showed a greater rat of reduction in MFCV over sustained contraction (26.1 ± 10.7%) in comparison with VL muscle (20.1 ± 8.5%, P<0.025) 24 hours after eccentric exercise. The result indicated that eccentric exercise contributed to a larger reduction in MFCV within the VMO muscle as compared to the VL muscle.
Discussion: This may abolish the ability of VMO to counteract the lateral pull of the VL muscle during knee extension, thereby leaving the knee complex more vulnerable to injury.