Effect of floor slope and load carriage on standing posture

Posture has been linked to low back pain and other ailments. While heeled shoes have been investigated, the effect of floor slope and load carriage on posture has received little attention. Therefore, the goal of this investigation was to assess these factors. Twenty-one men and 22 women (all healthy) of college age provided university-approved informed consent prior to participation. After familiarization, subjects stood motionless on the slope (facing up and down at 10 degrees and 20 degrees as well as the level), then bent over picking up a milk crate from the floor (men = 25kg, women = 15kg), and returned to a motionless standing position with the crate at knuckle height. Six trials were performed in each condition with the last three averaged to produce representative results in both standing conditions for each slope. Right sagittal plane kinematics and surface EMG of the erector spinae and middle trapezius were recorded. A static inverse model calculated moments at L5/S1. Significant differences (p < 0.001) between standing with and without the load were observed in all variables (torso, hip, knee, and ankle angles, L5/S1 moment, and both muscle activities) except low back curvature (p = 0.217). Across the floor slopes, significant trends existed in the low-back, knee, and ankle angles when standing without the load (p < 0.001) while the same parameters plus hip angle and L5/S1 moment were significantly different across floor slope with the load (p < = 0.026). In conclusion, both floor slope and load carriage should be considered when assessing ergonomic factors related to standing posture.