Effect of load carrying on required coefficient of friction

BACKGROUND: A load carrying task was identified as a major factor leading to slip and fall injuries such as overexertion and bodily reaction. Holding a load in front of the body while walking would shift the whole body center-of-mass to the front, loading additional rotational torque at the foot-ground contact. OBJECTIVES: The present study evaluated if carrying a load would increase the likelihood of slip initiation and the slip severity. METHODS: Eleven young and 10 older adults participated in the present study. A dry surface or a slippery surface was introduced while walking. Slip distance, peak sliding heel velocity, heel contact velocity, and required coefficient of friction were measured to test the study hypotheses. RESULTS: The results showed that significant main effects were found in slip distance, and peak sliding heel velocity and no main effect were found in heel contact velocity and required coefficient of friction. CONCLUSION: In conclusion, younger adults were found to slip longer and faster on the slippery surface while carrying a load. On the contrary, the older adults employed a safety-centered gait adaptation while carrying, to maintain slip initiation and severity characteristics at the same level as normal walking. Furthermore, light load carriage at 10% of body weight was suggested as a safe task for the elderly.