Milad Zarrin - M.Sc Student in Physiotherapy, Student Research Committee, Ahvaz Jundishapur University of Medical Sciences,Ahvaz Iran
Mohammad Pouretezad - PhD in Physiotherapy, Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences , Ahvaz, Iran
Maryam Saadat - Maryam Saadat is Assistant Professor in Physiotherapy, Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Hadi Bazyar - Ph.D Candidate of Nutrition, Student Research Committee, Ahvaz Jundishapur University of Medical Sciences , Ahvaz, Iran

Background: Trunk flexion caused by bending and lifting activities is associated to an increased risk of emerging spinal problems. Previous research studies have shown that number of factors such as the magnitude of load, loading rate, fatigue, creep developed by prolonged lumbar flexion, can cause alterations in flexion relaxation phenomenon (FRP) in healthy subjects. in most environments involves cognitive stress, it is important to know the effects of cognitive loading on the biomechanical parameters such as FRP.So the objective of this research was to examine the impact of cognitive loading on the flexion relaxation phenomenon (FRP) during trunk flexion and return from flexion task. [Subjects and Methods:Twentytwo healthy subjects (۱۸ males, ۴ females) participated in the study. ۳ experimental conditions were studid: no cognitive task, easy cognitive task, and difficult cognitive task. Surface electromyography was used to measure lumbar erector spine muscles activity level. The fexion relaxation ratio (FRR) was compared to assess the differences between the three experimental conditions during flexion and extension (FLX FRR and EXT FRR). Results: The FRR decreased with an increase in cognitive difficulty; the difficult cognitive task was associated with significant lower value of FLX FRR on both sides. However, these changes were not significant in easy cognitive task. In addition, the EXT FRR decreased in cognitive task conditions, but these results were not statistically significant except for difficult cognitive task in comparison to no cognitive task condition on left side. Conclusion:These findings showed that cognitive loading can affect FRP in healthy subjects.

Chronic nonspecific low back pain, lumbar clinical instability, lumbopelvic rhythm