The exact and direct measurement of the muscle activity in the human body is important for the diagnosis of diseases and for the performance measurement of athletes. In particular, the detection of muscle trembling (so-called tremor) under a certain load could be an accurate measure of the progression of diseases or of the muscle’s capability. Until now mostly invasive or contact-based measurement principles have been used for this application. The authors show the development of a setup for an optical measurement of muscle activity which is proven to be capable of measuring fine frequency and amplitude differences of oscillating surfaces in technical and medical applications. Furthermore, the authors show the measurement performance of their method in comparison to an established method. The authors can prove that their method has good applicability for measuring the amplitude and frequency of the tremor remotely and that the results are consistent with mechanomyographic measurements of the tremor.