EMG Features as an Indicator of Muscle Strength for the Assessment of Non-Specific Low Back Pain

Nonspecific low back pain is attributed to improper posture and characterized by muscle weakness. Treatments begin with evaluating muscle strength based on a manual muscle testing (MMT) protocol, a method that is considered highly subjective. Electromyogram (EMG) features that are intuitively related to the underlying strength of muscles can be used as an alternative to MMT to grade muscles. Bilateral muscles of the core trunk, namely the longissimus thoracis (LT), iliocostalis lumborum (IL) and lumbar multifidus (MF), of low back pain patients were examined. Surface EMG signals were acquired simultaneously while performing MMT by a trained physiotherapist who assigned grades 4-,4, 4+ or 5 on the Medical Research Council (MRC) scale. A Gaussian mixture model was used for unsupervised clustering into one of the grades based on the EMG feature information. Moderate agreement (? = 0.48) was found between MMT- and EMG-based methods. Bilateral symmetry observations revealed mild asymmetry between sides in the LT muscle. The comparative advantage of EMG-based strength testing over the manual method was proved. Additional information on muscle physiology and its manifestation during back pain as reported from the featured information will be useful for physicians to decide on treatment planning.