Evaluation On The Carrying Property Of Backpack During Walking And Jogging

Backpacks play an important role in outdoor enthusiasts,students and soldiers,more and more people use backpacks to carry belongs.Current research concentrated on biomechanical and physiological effects caused by various load carrying,the direct interaction between a backpack and a human body still remained unclear.In this paper,the interaction was investigated and a method based on the vibration and pressure measurement was proposed to evaluate the carrying property.A backpack was used for the experiment.The Vicon motion capturing system was used to capture the movement of the body torso and the backpack as well.The left and right clavicles,and the left and right anterior superior iliac spines were used to build a reference plane for a Local Coordinate System(LCS)to represent the motion of the torso.The backpack movement at three locations was captured at the same time with the body and then the displacements of these points was transferred from the Global Coordinate System(GCS)to LCS,to obtain the movement of the backpack relative to the body.The pressure was measured at shoulder,waist and hip,during the body is standing uprightly,walking(4.5 km/h)and jogging(6.5 km/h)respectively.The dynamic pressure was further linked to the displacements of the backpack obtained.Five female undergraduates volunteered to participate in the experiments.To investigate the effect of belts,the various tying conditions of belts were tested.The results are as follows.1)The displacement of backpack relative to the body showed cycled change with the body movement.During walking,the displacement in the left-right direction was the greatest,and was up to 18.5 mm;during jogging the displacement in the vertical direction became the greatest and was up to 31.9 mm.During jogging,the tying of waist belt reduced the vibration of backpack in the left-right and the vertical directions(up to 8,6 mm).From walking to jogging,the vibration in the vertical direction increased by up to 24.3 mm.2)During standing,the pressure at the shoulder could be high as 9.4 kPa,it could be reduced by tying the waist belt.During walking,the pressure at the shoulder increased significantly,by up to 2.8 kPa,and by tying the waist belt,the pressure at the shoulder reduced by up to 0.6 kPa,while the pressure at the waist and hip increased.During jogging,the pressure at the shoulder and hip reduced.3)The dynamic pressure showed cycled change simultaneously with the displacements.When the backpack reached the highest position,the acceleration in the vertical direction became the maximum and the pressure at the shoulder reached a peak,the amplitude of the pressure change was up to 1.1 kPa.When the backpack pressed the hip,the acceleration in the front-rear direction reached a peak and the pressure at the hip reached the highest value,the amplitude of the pressure change was up to 0.8 kPa.In conclusion,the method based on the vibration and pressure measurement was confirmed to be feasible to evaluate the carrying property and identify difference between backpacks.