The Effect of shoulder strap design and mechanical properties on the surface pressure of bike backpacks

Abstract

For a number of reasons, comfort in bike backpacks is increasingly important. Considering the longterm effect, discomfort can lead to severe injuries or at least pain especially in the shoulder region. An alternative to subject studies is the determination of discomfort by detecting the surface pressure. However, until today there is no previous study which investigates the comfort or the surface pressure in bike backpacks. The aim of the present study was to evaluate the effect of shoulder strap design and material properties in bike backpacks on the surface pressure. Fourteen healthy male subjects carried 6 different backpack configurations while cycling on a stationary bicycle in brakehood position. The backpack configurations differed in shape and padding material at the shoulder strap. The surface pressure was measured with a piezoelectric pressure mapping system. The results revealed that shoulder strap design as well as the material properties could affect the average and peak surface pressure. The modified strap shape showed a significant lower average and peak surface pressure compared to the original backpack. In addition, it has been shown that the use of a relatively stiff PE material in combination with a soft foam as a double layer padding can lead to a significant decrease in average surface pressure compared to shoulder straps with common foam padding or mesh.