ABSTRACT
Hand-handle interface, which induces varied wrist posture, is seldom considered in most of the current upper limb biomechanical analyses of pushing and pulling strength. In our laboratory a study was developed to examine effects of handle rotation in the frontal plane (0°-horizontal, 45°, and 90°-vertical), anterior tilt (0°- parallel to the frontal plane, and 15°), and distance between two handles (31 and 48.6 cm) on pushing strength. A special testing station was constructed to measure upper limb push exertions with minimal contribution from the torso and legs. Both the horizontal (forward pushing) and vertical components of the pushing forces were measured within the station. Thirty-one study participants were recruited for the seated two-hand pushing strength tests. Referencing to the horizontal, straight, and a 31 cm between-handle distance handle configuration, the 45°-rotated and tilted handles with a 31cm between-handle distance allowed 6.7% more pushing output, while the horizontal and tilted handles with a 31cm between-handle distance resulted in 2.8% less. Subjective preference was correlated with normalized pushing strength (r=0.89). Tilted handles, at 45°-rotated and vertical positions received highest subjective ratings of preference among all handle configurations. Women exerted the greatest strength when the handles were the 31-cm apart, while men exerted more pushing strength with the 48.6-cm handle distance. The results demonstrated that pushing capacity was affected by handle rotation and tilt angles, and therefore such design should be taken into consideration when evaluating pushing tasks.
