RESUMO
Background: epidemiological evidences have showed that low back pain fallowing load-carrying is the most common disorder in musclo-skeletal system and is common in industrialized countries.Moreover, little is known about how muscles are recruited when several option of the accomplishment of task are available. Thus this study aimed to examine the effects of external load and trunk posture on the electromyography activity of trunk muscles
Materials and methods: 10 healthy women with no history of low back pain were enrolled in this study. Two inclinometers and five channel EMG system were used to evaluate the right trunk muscle activities [rectus abdominis, internal and external oblique, erector spine, and multifidus]. Six static tasks while holding three levels of load [0, 6, 12 Kg] in two trunk position [neutral and 30 degree of flexion] were simulated for subjects
Results: with highest external load, the electrical activity of back and abdominal muscles increased significantly and with highest trunk flexion, the electrical activity of back muscles increased significantly [P<0.05]
Conclusions: co-contraction of back and abdominal muscles occurred in response to greater need for biomechanical stability. The increased extensor muscles activity during trunk flexion is necessary for stability and controlling of flexion
RESUMO
Epidemiological studies have shown that low back pain after load-carrying is an important and costly disorder in muscolo-skeletal system. Lumbar curvature is an important factor in posture and body movement that may assist us to evaluate how low back pain problems may develop. Differences in lumbar inclination affect the vertebral stresses. The object of this study was evaluation of the affects of external load and trunk posture on lumbar curvature under static condition. Ten healthy female subjects with no history of low back pain were participated in this study. Two inclinometers were used to evaluate the lumbar inclination. Six static tasks while holding three levels of load [0, 6, 12 Kg] and two levels of trunk position [neutral and 30 degree of flexion] were simulated for subjects. Trunk position [30 degree of flexion] and external load [6, 12 Kg] both had significant effects on lumbar inclination and reduce lumbar lordosis [p < 0.05]. Lumbar lordosis reduced while holding load, so muscles activity and may reduce tissue injuries reduced. Increased lumbar kyphosis shown resulted in trunk flexion is a lumbar supportive factor for compressive stresses
RESUMO
Epidemiological studies showed that low back pain is one of the most important disorders in musculo-skeletal system. This disorder is common in industrial countries. Low back pain is the common care of human dysfunction and economical problems. Balance is necessary for performing activities in daily living [ADL], and it should be considered in patients with low back pain. Physiological components of afferent and efferent fibers that control balance, muscle stiffness., strength and endurance are often impaired in such patients. Peripheral components of balance include: 1] The somatosensory system which is the most important component and includes repositioning sense, kinesthesia, joint position sense and duration of muscle contraction. 2] The visual system and 3] The vestibular system. According to this literature review balance, repositioning, kinesthesia and postural control which were impaired in chronic low back pain patients might be due to change in transmitted information by mechanoreceptors, paraspinal muscle spindle dysfunction, muscle strength and coordination, delay in muscle recruitment or increased active muscle tension. Changes of proprioception are the most important factor of impaired balance in low back pain patients