An optimal effective working height for hammering tasks.

Background: Hammering is a functional task in which the wrist generally follows a path of motion, however, previous studies paid relatively little attention to it.

Objective: The main objective of this study is to determine the optimal working height while using a straight-handled hammer to perform the hammering task.

Methods: Ten participants performed the hammering tasks on three different working heights (64, 80, and 96 cm) using three subjective hammering forces (light, medium, and heavy).

Results: The results revealed that there were linear increasing trends of shoulder abduction, which increased with the increased working height when hammering and the trunk flexion revealed a contrary result. However, the ulnar deviation and trunk lateral bending were insensitive to the working heights. The hammering forces merely resulted in trunk flexion and lateral bending and no posture differences at upper extremities.

Conclusion: The trade-off between acceptable trunk flexion and shoulder abduction was considered to determine a reasonable effective working height (by measuring downward from worker's elbow height) in the range from 25 cm to 35 cm with a mean 30 cm. This range will be valuable for hammering job design.