Theoretical optimization of usage of four-wheeled walker and body posture of elderly users for comfortable steady walking.

Usage of a four-wheeled walker and body posture of elderly users is optimized by a two-dimensional statics model for comfortable steady walking. Analytical results suggest that fundamentals of body posture for comfortable walking should be as upright as possible. However, usage of the walker varies with exercise capabilities of elderly users. Users with high capabilities should use a higher handgrip for maintaining upright posture. Stooping users with low capabilities should use a lower handgrip, should maintain an erect trunk as much as possible, and should push the handgrip downward by leaning their upper body on the walker.