The effect of load mass and its placement on postural sway.

The purpose of this study was to investigate the effects of increasing load on postural sway in two different carrying positions: backpack and waist jacket. Potential differences between males and females were additionally evaluated. 60 young college students participated in this study, and were assigned to backpack and waist jacket groups. The loads in both groups were 12, 21 and 30 kg. Stabilometry was used to assess the amount of postural sway. The medio-lateral and antero-posterior mean sway, mean velocity, medio-lateral and antero-posterior path length and sway area of the centre of pressure position were calculated. In the backpack group all analyzed sway parameters linearly increased with additional load, the differences were significant at p < 0.001. However no significant change of the analyzed parameters was found when the subjects carried additional load in the waist jacket. Our results indicate that postural sway depends on the amount of the load carried in a backpack. Additionally, the position of the load is of significant importance. Carrying weight in a backpack increases postural sway with increasing weight whereas carrying weight in a waist jacket does not influence the amount of postural sway. There are no significant differences in the response to the amount and configuration of the load between male and female subjects.