Science Update - Backpacks and Chairs

Chelsea and Bob look at a new bungee backpack and how you should sit in a chair
21 January 2007

Interview with 



Chelsea - Whether you're a hiker, a paramedic, or a third grader, a heavy backpack can be a real pain. Now, University of Pennsylvania muscle physiologist Larry Rome has designed an ergonomic pack that can lighten the load and potentially prevent injuries. It's rigged with a springy, stretchy bungee cord, which allows the load to glide up and down on a frame as you walk. That eliminates the exertion of lifting the pack a few inches every time you take a step.

Larry Rome (University of Pennsylvania): The bungee cord stretches so the load stays at the same height with respect to the ground. If the load doesn't move with respect to the ground, then it doesn't have to be accelerated, and there's no accelerative force.

Chelsea - That may sound trivial, but Rome says these peak forces can double or even triple a pack's load while you're walking or running. In contrast, the bungee pack's effective load stays very close to its actual weight.

Bob - Thanks Chelsea. If you sit for a living, the common wisdom that you should sit up straight could be wrong. This according to Asim Bashir, a musculoskeletal radiologist at the university of Alberta in Canada. He and his colleagues used a new full body MRI scanner to study various sitting positions.

Asim - Sitting up bolt straight, 90 degrees with your back straight and your legs parallel to the floor increases the amount of pressure in your lower back discs, adds strain on your ligaments and muscles, and also causes squashing of the discs when you're in that position.

Bob - They found that it's much better to recline slightly with your knees well below your hips, creating a wide angle between your thighs and torso. That's hard to do in most office chairs, but Bashir says putting a wedge shaped cushion under your back and raising the seat height can help. Unfortunately they found that slouching, which is what most of us do, is still not smart.


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