  We investigate the relationship between synchronized muscle activity and
tremor time series in (enhanced) physiological tremor by cross-spectral
analysis. Special attention is directed to the phase spectrum and its
possibilities to clarify the contribution of reflex mechanisms to physiological
tremor. The phase spectra are investigated under the assumptions that the EMG
synchronization was caused by a reflex, respectively a central oscillator. In
comparison of these results to phase spectra of measured data we found a
significant contribution of reflexes. But reflexes only modify existing peaks
in the power spectrum. The main agents of physiological tremor are an efferent
pace and the resonant behavior of the biomechanical system.
