Comparison of Symmetrical and Asymmetrical Bag-Carrying on the Vertical Ground Reaction Force During Walking in Healthy Adults

Objective Symmetrical and asymmetrical bag carrying during repetitive activities such as walking may increase mechanical loading and potentially elevate the risk of musculoskeletal injury. Analysis of ground reaction forces (GRF) during walking is therefore of clinical relevance. The aim of this study was to investigate the vertical ground reaction force during different symmetrical and asymmetrical bag-carrying conditions. Methods Seventeen female university students voluntarily participated in this study. Vertical ground reaction force data were recorded using an RSscan foot scanner at a sampling frequency of 300 Hz. Two asymmetrical carrying conditions (single-hand carrying and single-shoulder carrying) were compared with two symmetrical conditions (backpack and front pack). Results Carrying a bag with one hand resulted in a significantly higher loading rate compared with single-shoulder carrying (P = 0.007) and backpack carrying (P = 0.005). However, no significant difference in loading rate was observed between single-hand carrying and front-pack carrying (P = 0.051). The time to peak vertical ground reaction force at heel contact was significantly shorter during front-pack carrying compared with single-hand carrying (P = 0.03). Conclusion Single-hand bag carrying is associated with a significantly greater loading rate compared with single-shoulder and backpack carrying. Given that these impact forces are applied at every heel strike during walking, minimizing single-hand bag carrying may help reduce repetitive mechanical loading.