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The week in Biomechanics #CW25

Lasse Hansen 0

The weekly recap of what is going on in the world of biomechanics.

You might have heard bout ‘Floating Backpacks’ or suspended-load backpacks, which is the more technical term. These backpacks aim to reduce strain on the back and shoulders through a novel fixation technique. Recently, a paper was published that had a look at this idea from a biomechanical point of view. Check out the video below to get an idea what this is about, but also note we are not sponsored or affiliated with the manufactures in any way. Enjoy the read!

Physiological and biomechanical effects on the human musculoskeletal system while carrying a suspended-load backpack

The idea seems pretty straight forward, if you walk (or run) with a normal backpack, you get peak forces whenever your center of mass is lowest during your stride cycle. The backpack is moving downwards and has to be decelerated, thus creating a force that is higher than the sole weight of the backpack times Gravitational force. Mechanically speaking, as long as the backpack is not moving vertically, no work has been afforded. And yes, that’s nothing you want to hear after a long walk.

So this group of researchers around Longhan Xie from Guangzhou (South China) aimed to determine ”the impact of different types of backpacks on metabolic cost, joint kinetics, gait kinematics, and muscle activity” [1].

For this purpose, the researchers took six healthy subjects, gave them 15kg of load in a backpack, and made them walk (5km/h) and run (7km/h) on an instrumented treadmill. Three different Backpack-Conditions were tested, a suspended load back in its suspended condition, the same backpack but in a locked condition, and one ordinary backpack.

The group actually did find a reduction in lower limb muscle activity and joint work (15.25 ± 4.21% during walking, 12.53 ± 2.39% during running). Furthermore, a reduction in metabolic cost was found (8.81 ± 2.46% during walking, 6.99 ± 2.37% during running) when compared to the other backpack-conditions. Since the paper is not freely accessible, we lack detailed information here. It would be nice to know how the metabolic cost was measured (though we just assume it’s been a spiroergometry) and whether there were differences in the suspended load backpack and the ordinary backpack.

However, it is interesting to see that the idea of a suspended-load backpack appears to fulfill its promises to an extent. Yet it appears to be a bit confusing that the effects seemed to be greater during walking compared to running since you would expect greater vertical forces during running. Maybe future studies bring more insight into this topic, still, we found the core of the study interesting and thought you might like it too.

See you next time!

[1] Huang, L., Yang, Z., Wang, R., & Xie, L. (2020). Physiological and biomechanical effects on the human musculoskeletal system while carrying a suspended-load backpack. Journal of Biomechanics, 109894.

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