  EMG is an established method to acquire the action potentials of contracted
muscles. Although commercial EMG systems are available and it is one of the
most researched biosignals, it has never become widely used in rehabilitation
or fitness training monitoring. The reasons are technical challenges of
wearable EMG systems regarding electrode placement, motion artefacts and the
complex connectivity of multi-channel EMG measurements. We address this problem
for the lower back and abdominal musculature, through a novel dry electrodes
belt, multi-channel high density EMG circuitry and problem-specific signal
processing. The subject can easily strap the dry electrodes belt around himself
which provides 16 EMG channels. Interferences from the ECG and motion artefacts
are reduced by a stationary wavelet decomposition. Afterwards, an inter-channel
filter is applied to increase the robustness of the signals. Subject
measurements during different kinds of typical abdominal and lower back
training exercises were performed wearing the novel dry electrodes belt. The
results show the possibility of robust EMG measurements from the lower back and
abdominal muscles by utilizing the gathered redundancy, appropriately. The
additional information obtained via the multi-channel EMG circuitry and spatial
oversampling can be used to address current problems of EMG applications. It
combines the advantages of robustness and the capability of using comfortable
dry electrodes. Therefore, the proposed measurement method for acquiring
spatial information about the muscle contractions from the lower trunk can be
used for rehabilitation or fitness training monitoring.
