The effect of back extensor muscles fatigue on the thickness of abdominal muscles after lifting task in healthy women

Document Type : Original Articles


1 MSc, Department of Physical therapy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

2 Assistant professor, Department of Physical therapy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

3 MD, Department of Orthopedics, Tehran University of Medical Sciences, Tehran, I

4 Instructor, Department of Biomedical Engineering, Faculty of Engineering, Islamic Azad University, Dezful Branch, Dezful, Iran



AbstractIntroduction: Back muscles fatigue is one of the risk factors in workplace and throughout daily activities. Under fatigue conditions, loads will be redistributed among active and passive tissues in a non-optimal manner, where a single tissue may become overloaded and thus increasing the risk of injury with minimal loads. Because of the importance of abdominal muscles in producing and maintaining spinal stability in unstable conditions, it was necessary to investigate the response of these muscles in the presence of back muscles fatigue. Since it is not possible to study deep muscles with surface electromyography (EMG) techniques, in this study the function of abdominal muscles after lumbar extensor fatigue was investigated by ultrasound imaging technique.Materials and Methods: Fifteen healthy women participated in this experimental study. Abdominal muscles thickness was measured from the lateral abdominal wall (Transverse abdomen (TrA), Internal oblique abdomen (IO), External oblique abdomen (EO)) using ultrasound imaging technique before and after the back extensor muscles fatigue protocol in upright standing with and without axial loading  equal to 25% of the participants’ body weight. Repeated measure ANOVA was used to test the main effects of the load and back extensor muscle fatigue on the thickness of the abdominal muscles.Results: Although, symmetric axial loads equal to 25% of each participant weight had no significant effect on the thickness of abdominal muscles, back extensor muscles fatigue increased IO thickness significantly(P=0. 009).Conclusion: The results showed that abdominal muscles response changes with back extensor muscles fatigue. By increasing the thickness of abdominal muscle, the stability of the spine could be maintained.Key words: back extensor muscles fatigue, thickness, abdominal muscles, load