Mechanomyography (MMG) is a technique for recording mechanical activity in contracting muscle. The MMG signal is low frequency, typically 5-100Hz.This MMG ‘sound’ is produced by lateral oscillations of muscle fibres which occur at the resonant frequency of the muscle. The analysis of MMG signals has allowed examination of various aspects of muscle function such as neuromuscular fatigue, muscle fibre type distributions and neuromuscular disorders. To date, Electromyography (EMG) has been considered the primary non-invasive technique to record and interpret the physiological properties of contracting muscle. The Hoffmann reflex (H-reflex) is the equivalent of the monosynaptic stretch reflex, elicited by electrical stimulation. The aim of this investigation was to characterise the Hoffman reflex using an MMG system. The system is based on 2-axis MEMS (Micro Electro-Mechanical System) sensors placed on the soleus muscle.