Biomechanical analysis and characterization of muscle synergies and motor control quality in the context of manual material handling

Low back pain (ICF: b28013, pain in back) is a leading cause of years lived with disability worldwide and may be associated with impairments in body functions, activity limitations, and participation restrictions within the biopsychosocial framework of the World Health Organization’s International Classification of Functioning, Disability and Health (ICF).

My dissertation applied ecological task analysis to lifting and lowering tasks (ICF: d4300, lifting; d4305, putting down objects), systematically manipulating four task factors across 16 experimental conditions: horizontal and vertical load distance, movement asymmetry, and load stability. Using the Uncontrolled Manifold (UCM) method, I quantified how these task constraints influenced the organization of trunk muscle activity in healthy participants, examining the variability associated with maintaining a defined performance variable versus variability that disturbed it.

The direct contribution was to demonstrate experimentally that changes in task demands modify the organization of trunk neuromuscular control. By combining ecological task analysis with UCM-based quantification, the dissertation provides a mechanistic approach to investigating person–task–environment interactions during functional lifting tasks. These findings establish a foundation for future research into individualized physical activity and rehabilitation interventions for people with low back pain, with potential relevance to functioning in daily activities and participation in employment (ICF: d850), recreation and leisure (ICF: d920), and sports (ICF: d9201). These clinical and participation outcomes remain to be tested in the relevant populations.