Arm motion and load analysis of sit-to-stand, stand-to-sit, cane walking and lifting

To conduct a pilot study to characterize the hand loads, arm joint angles and external moments corresponding to five activities of daily living demanding of the shoulder, for healthy subjects over 50 years of age.

The tasks were sit-to-stand, stand-to-sit, cane walking, lifting a 5 kg box with both hands, and lifting a 10 kg suitcase.

Arm motion and loading have not been previously studied for functional daily-living tasks involving substantial external loads.Methods. Motion was tracked using an optoelectronic system. Loads were measured using an instrumented chair arm, a force plate, and gravitational and acceleration loads. Six healthy volunteers (3 male, 3 female), mean age 55, with no history of shoulder problems participated in the study.

Average peak external moments ranged from 12.3 N m for sitting down into a chair to 27.9 N m for lifting a suitcase. Except for lifting the box, which had much lower loads, average peak hand loads varied from 16% to 19% of body weight (114-134 N). The arcs of motion were larger than for seated activities of daily-living studied previously.

The five tasks studied are commonly performed, yet involve large external moments. Lifting represents the greatest potential loading at the shoulder as it resulted in the highest external moments; furthermore, loads larger than those used in this study might be commonly lifted.

External moments at the shoulder should not be underestimated, even for activities of daily living.