Backs bear a heavy burden

Tel Aviv University (TAU) researchers say that using backpacks can lead to nerve damage, specifically to the nerves that travel through the neck and shoulders to animate hands and fingers.

Professor Amit Gefen of TAU’s Department of Biomedical Engineering and Professor Yoram Epstein of TAU’s Sackler Faculty of Medicine, along with PhD student Amir Hadid and Dr Nogah Shabshin of the Imaging Institute of the Assuta Medical Center, have determined that the pressure of heavy loads carried on the back have the potential to damage the soft tissues of the shoulder, causing microstructural damage to the nerves.
The result could be anything from simple irritation to diminished nerve capacity, ultimately limiting the muscles’ ability to respond to the brain’s signals, inhibiting movement of the hand and the dexterity of the fingers. In practice, this could impact functionality, reducing a worker’s ability to operate machinery, compromise a soldier’s shooting response time, or limiting a child’s writing capacity.
The research was published in the Journal of Applied Physiology and partially supported by a grant from TAU’s Nicholas and Elizabeth Slezak Super Center for Cardiac Research and Biomedical Engineering.

Impaired function
Focusing their study on combat units in which soldiers must carry heavy backpacks, the researchers discovered that, in addition to complaining of discomfort or pain in their shoulders, soldiers also reported tickling sensations or numbness in the fingers.
Exploring this issue in a non-invasive manner, they used biomechanical analysis methods originally developed for investigating chronic wounds. The analyses show how mechanical loads, defined as the amount of force or deformation placed on a particular area of the body, were transferred beneath the skin to cause damage to tissue and internal organs.
Based on data collected by MRI, Professors Gefen and Epstein developed anatomical computer models of the shoulders. These showed how pressure generated by the weight of a backpack load is distributed beneath the skin and transferred to the brachial plexus nerves. The models also account for mechanical properties, such as the stiffness of shoulder tissues and the location of blood vessels and nerves in the sensitive areas which are prone to damage.

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