Background and Objectives: Core muscles of individuals with low back pain show a different pattern of activity compared to the healthy group during load lifting. This issue may be due to changes in spinal control mechanisms such as muscle synergies. The aim of this study was to compare the synergy pattern of selected core muscles and lower limbs muscles during load lifting and lowering with two different techniqus among females with non-specific back pain in comparison with healthy group.

Methods: Eighteen healthy females with non-specific back apin and 18 match controls participated in this study. The activity of 8 muscles of the core and lower limbs was recorded while lifting a load of 10% of the subject's mass with stoop and squat techniques. Then, using non-negative matrix factorization algorithm, the pattern of muscle synergies was extracted. Pearson's correlation method and independed t-test was used to compare synergy patterns (p<0.05).

Results: Patients with back pain had a different muscle synergy pattern compared to the healthy group in both stoop and squat techniques. The peak muscle synergy patterns of patients in both techniques were different from healthy subjects and were created in a different time cycle of lifting the load.

Conclusion: The results of this study showed that individuals with non-specific back pain use different synergy patterns during load lifting, and the body's control system may respons differently in patients with non-specific low back pain compared to healthy individuals. It is possible that the changes observed in the relative weight of muscles in patients and healthy people are caused by the changes in muscle synergy patterns, which requires further studies.