Stability in the lumbar spine is ensured by both the passive joint mobility and active stability provided by the muscles. The latter produce the movements and control them, to provide a normal functioning of the spine. The physiotherapist should be able to identify the faulty movements and correct it according to the imbalanced length and strength of the involved muscles (Norris, 1995).
A good posture is defined as “the state of muscular and skeletal balance which protects the structures of the body against injury or progressive deformity, irrespective of the attitude in which these structures are working or resting”. In the predefined conditions, muscles acting over a joint will work in their optimal position and therefore more efficiently. If there is a wrong posture, the positioning of the muscular and skeletal structures is faulty, increasing the possibility of strains and injuries (Kendall et al. 2005).
Janda believed that the cause of muscle pain is damage to muscle or connective tissue, trigger/tender points as well as muscle spasm causing ischemia and fatigue. Muscle imbalance can generate because of pain, leading to a muscle response to protect the area. Postural changes are common to avoid and protect the injured area, but these compensations lead to a decrease in range of motion and an altered movement pattern creating further muscle imbalance. As negative reinforcement, the repeated faulty movement become centralized in the central nervous system. These movements and muscle imbalances eventually lead to an alteration in the position of the joint, causing inefficient distribution of stress and altered proprioception. Ultimately there may be joint degeneration and chronic pain facilitating the vicious cycle even more (Page et al. 1967; Page and Frank, 2002).
Janda and Jull classified the muscles into postural and phasic types. This is based on the concept that muscles for maintaining an upright posture (postural or tonic muscles), are more inclined to become tight and hypertonic. Whereas other muscles, the phasic muscles, become weaker and inhibited in reaction to stress and injury. The imbalance pattern occurring at the lumbar-pelvis region is called pelvis/lower crossed syndrome. Muscles in this region work on two diagonals, thus when imbalance occurs it is most likely that muscles on one diagonal will be tight and hypertonic weather muscles of the other diagonal would be weakened and lengthened. In the specific case, hamstrings, hip flexors, rectus femoris and lumbar erector spinae are short and tight while abdominals and glutes are lengthened and weak. The muscular situation create the known pattern of increased lumbar lordosis and anterior pelvic tilt (Magee, 2006).