Autonomic Nervous System (ANS) function has been assessed in several muscular dystrophies. In the last two decades it has been recognized a significant relationship between ANS and cardiac mortality (Politano et al., 2008). Cardiovascular ANS is frequently studied by using cardiovascular autonomic reflex tests and spectral analysis of heart rate in time and frequency domain (Ewing and Clarke, 1982; van Ravenswaaij-Arts et al., 1993). Heart rate variability (HRV) analysis, which involves measurement and analysis of heart rate variation, provides a quantitative marker of autonomic activity and has proved to be able to detect and measure modification in sympathetic or vagal activity. Moreover, it can be used to estimate the susceptibility for heart arrhythmias (Heart rate variability, 1996a,b).