Upper limb and trunk kinematics in tree planters during three load carriage conditions.

Tree planters use various strategies to unload the seedlings from their bags. This study examines differences in upper limb and trunk joint angles during three load carriage conditions: (1) load evenly distributed to the right and left sides of the body - evenly loaded (2) load entirely on the right side - right loaded and (3) load entirely on the left side - left loaded. Data were collected in the field in Northern Ontario. Inertial motion sensors were placed on the right hand, right and left forearms and upper arms, sacrum, and T1 vertebrae. Using relative sensor orientation, joint angles were determined for the right wrist, right and left elbow and the trunk for the three load carriage conditions during normal planting tasks. The main findings were: 1) In the left loaded condition, the right wrist was less extended, the right elbow was more flexed, the trunk experienced less right-rotation, and the right and left forearms were less pronated than in either the evenly loaded or right loaded conditions. 2) In both the left and right loaded conditions, the left forearm was less pronated, and the trunk was less flexed than in the evenly loaded condition. Results suggest that asymmetrical tree load carriage results in more neutral postures than symmetrical tree load carriage. [ABSTRACT FROM AUTHOR]