Maximal push/pull strengths in the vertical and horizontal directions with hands above shoulder level

Very little information is available to set guidelines that can reduce injuries for pushing and pulling in the vertical and horizontal direction when the arms are above shoulder level. The long term goal of this study was to be able set guidelines or make recommendations that could be implemented in industry for pushing and pulling in the vertical and horizontal directions with arms above shoulder level. The null hypotheses of this study were that there were no significant differences between the four heights of the maximal voluntary force exertion (180°, 150°, 120°, and 90° arm angle), the type of force applied (push or pull) or as the distance between the left and right hand was changed. Subjects were asked to push/pull on a handle that allowed for the two distances between the hands at the four different arm angles in the vertical and horizontal direction. Therefore, data were separated based on the vertical and horizontal direction. With 25 males and 25 females, significant main effects were found in the horizontal direction for gender (F(1,48) = 8.32, p < 0.01), force type (F(1,48) = 5.825, p < 0.05) and arm and arm angle (F(3,144) = 84.763, p < 0.001). In the vertical direction, significant main effects were found for gender (F(1,48) = 113041, p < 0.01), force type (F(1,48) = 81.27, p < 0.001), arm angle (F(3,144) = 76.08, p < 0.001), and also distance between the hands (F(1,48) = 45.939, p < 0.001). Additional interactions were also found to be significantly different for the horizontal and vertical directions. In the horizontal direction, the 90° arm angle produced the greatest maximum voluntary exertions. In the vertical direction it became a bit more complicated. When pushing in the vertical direction, the 150° arm angle produced the greatest maximum voluntary exertions. When pulling in the vertical direction, the 180° arm angle produced the greatest maximum voluntary exertions. Using a distance of approximately shoulder width apart only influenced push/pull strength in the vertical direction.