Evaluation of Central and Peripheral Fatigue in Vastii Muscles Using Semg Fractal Dimension and Muscle Fiber Conduction Velocity

Beretta Piccoli, Matteo and Cescon, Corrado and Clijsen, Ron and Barbero, Marco (2013) Evaluation of Central and Peripheral Fatigue in Vastii Muscles Using Semg Fractal Dimension and Muscle Fiber Conduction Velocity. In: 3° Congresso Nazionale SIF, 24-25 Maggio 2013, Napoli.

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Abstract

BACKGROUND and AIM Over the past decade several new sEMG descriptors for central fatigue have been developed and tested in simulation studies or in healthy subjects. Mesin and colleagues (2009) proposed a novel vector composed of two indexes: ECV (estimated conduction velocity) as indicator of peripheral fatigue and FD (fractal dimension) as indicator of central fatigue. FD is a promising index, least affected by MFCV changes and mostly related to MU synchronization. FD was never tested during a fatiguing task in healthy subjects, nor in patients. The aim of the study is to analyze if the vector developed by Mesin can be used as a bi-dimensional marker for central and peripheral fatigue in healthy subjects. MATERIALS and METHODS Twenty nine healthy female students participated in the study after providing informed consent. None of the subjects had previous injuries of the lower limb and all participated regularly in different exercises and sports. Myoelectric signals were detected from the vastus lateralis and vastus medialis in single differential configuration using bi-dimensional arrays. FD and MFCV were measured by sEMG during a low level isometric contraction (20% MVC) for one minute, in order to allow an evaluation of peripheral fatigue of type I muscle fibers, followed by an endurance isometric contraction (60% MVC) until exhaustion, in order to evaluate peripheral fatigue of type II muscle fibers. RESULTS Data on FD and MFCV are presented in Table 1. The average time course of MFCV (top, blue) and FD (bottom, red), during the 20% MVC and the 60% MVC isometric contractions is depicted in Figure 1. DISCUSSION The statistically relevant decrease of FD during the 60% MVC endurance contraction is consistent with an increase of MU synchronization, one of the indicators of central fatigue. Whereas the decrease of MFCV during the same fatiguing contraction, as previously observed, is a clear sign of peripheral fatigue. CONCLUSIONS This study demonstrated that the bi-dimensional index (MFCV, FD) is an effective indicator to differentially assess central and peripheral components of neuromuscular fatigability, with potential application in both clinical and sport sciences. KEYWORDS Muscle fatigue, surface electromyography, conduction velocity, fractal dimension ACKNOWLEDGEMENT Thim van der Laan Foundation for funding the study

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