We considered the change in joint stiffness as a motion strategy in human lumbar extension movement. We developed a musculoskeletal model that can reproduce this motion strategy and attempted to clarify the individual characteristics and differences in motion strategy. This model reproduces changes in lumbar joint stiffness during movement by appropriately adjusting parameters such that they represent the motion strategy. Using this model, we identified parameters in lumbar extension exercises for six participants with differences in lumbar joint stiffness and examined changes in lumbar joint stiffness and motion strategies. The results showed that participants with similar changes in joint stiffness had commonalities in their motion strategies.

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