A method for quantifying an intention of movement of a user, the method comprising: extracting a mechanomyogram (MMG) signal in response to surface vibration of a muscle of the user and averaging the MMG signal by calculating the MMG root mean squared (RMS) amplitude or frequency variance in a predetermined time window where an increasing RMS amplitude of the MMG signal corresponds to increasing muscle voluntary contraction or a decreasing frequency variance of the MMG signal corresponds to increasing muscle voluntary contraction.
