Investigation of electromyographic behavior of trunk muscles during prolonged load holding in subjects with hyperlordotic posture and normal subjects

The curves of the spine, especially lumbar lordosis, play an important role in the maintenance of an efficient upright posture and allow efficient absorption of the loads applied to the spinal column and increase the efficiency of the spinal musculature. Excessive lumbar postures, also called “hyperlordosis” and “hypolordosis”, are thought by some researchers to be indicative of altered muscle activity and stress patterns. Therefore tolerance of particular activities of daily living (ADL) of an individual with these postures is reduced. Despite the importance of neuromuscular control at spinal column maintenance and coordination, there are little investigations about the effect of thoracic and lumbar curvatures on trunk muscles activity. Therefore, the aim of this study was to investigate electromyographic behavior of trunk muscles in lordotic posture. Twelve subjects with lordotic posture (mean age 23.67 years, mean weight 56.67 kg, and mean height 162 cm) and eleven subjects with normal posture (mean age 22 years, mean weight 59.36 kg, and mean height 164.91 cm) participated in this study. Subjects were asked to hold a load equivalent of 7% of her body weight. Data analysis indicated that there is not significant statistically difference in median frequency variable between two groups (p>0.05). But there is significant statistically differences at The percentage change in RMS of erector spinae and internal oblique muscles at three time periods between two groups. The percentage change in RMS of external oblique muscle has significant statistically difference at first and third time periods between two groups. These finding reveal that excessive lumbar lordosis alter the activity levels of trunk muscles. Therefore, it seems that the use of posture correction exercises in therapeutic protocols is necessary for improvement of these changes. Also, it is recommended to do this research in dynamic tasks for attain of comprehensive information about the effect of postural deviation on electromyographic behavior of trunk muscles.