Segmental instability of the lumbar spine may cause functional disorders and strain as well as pain. It is supposed that paraspinal and abdominal muscles have the greatest capacity for enhancing the stabilisation of the spine. The intersegmental lumbar Multifidus has been shown to be more important than the other paraspinal muscles in stabilising the spine and in prevention of recurrence of back pain. In the literature and in clinical practice reduced endurance of back extensor muscles has been associated with back pain. In the past decades several investigators made to test back endurance with pain, functional and motivational factors. There is very little literature in support with Electromyographic EMG] analysis, which is a valid tool to objectively monitor the lumbar back extensor fatigue. Literature review shows that there is a great need of Non-invasive measures Surface EMG] to analyse the Multifidus function in low back pain.