Low Back Pain (LBP) is one of the most common chronic diseases. A group particularly prone to LBP is the parents of children with motor disabilities and the causes of LBP are weakened spinal stabilizing muscles and spinal overload during daily care activities. This work aimed to define the effects of strengthening individual groups of abdominal and dorsal muscles on the loads exerted on the lumbar spine in parents of children with motor disabilities. To obtain information on the kinematics of selected everyday activities (sitting down and getting up from a chair, lifting 10 kg and 20 kg objects from a table), experimental tests (using the APAS optical system) were carried out on the group of 30 mothers of children with motor disabilities. The obtained results constituted input data for conducting simulations in the AnyBody Modeling System to identify loads in the lumbar spine section (whole human body was used). The effect of the strengthening and weakening of abdominal and dorsal muscles (erector spinae, transverse abdomen, rectus abdominis, internal and external oblique abdominal muscles) was modeled by introducing different values for the physiological cross-sectional (PCSA) area of selected muscles. Component and resultant force values on the lumbosacral joint (L5-S1) of the spine and intra-abdominal pressure values were analyzed. The greatest reduction in the resultant reaction value at the L5-S1 joint was obtained in the simulations in which the TrA PCSA was increased. A double increase in the TrA PCSA caused a reduction of the resultant reaction in L5-S1 by 30% and the anterior-posterior and proximal–distal forces by approximately 20–30%. The observed effects of the TrA strength on spinal loads are a reflection of the interactions of the TrA with the spine through the modelled intra-abdominal pressure [1, 2]. REFERENCES [1] K. Nowakowska-Lipiec, R. Michnik, P. Linek, A. Myśliwiec, H. Zadoń, J. Gorwa. Effect of strengthening and weakening of abdominal and dorsal muscles on lumbar spine loads in parents of disabled children. Journal of Biomechanics, 161(111864), 2023. [2] K. Nowakowska-Lipiec, R. Michnik, P. Linek, A. Myśliwiec, K. Jochymczyk-Woźniak, K., Gzik, M., 2020. A Numerical Study to Determine the Effect of Strengthening and Weakening of the Transversus Abdominis Muscle on Lumbar Spine Loads. Comput. Methods Biomech. Biomed. Engin. 23, 1287–1296.