Second Spine: A device to relieve stresses on the upper body during loaded walking

The target of this work is to experimentally validate the Second Spine, a wearable device recently developed by our group to transfer forces from shoulder to pelvis during loaded walking. A key-feature of the Second Spine compared to traditional framed backpacks is the adjustable stiffness of its structure, which allows the wearer to change the load-bearing behavior of the device. In line with previous studies on loaded walking, we investigate biomechanical and physiological variables on a small group of young healthy subjects, as they walked on a treadmill under 3 different conditions: free walking, walking with a backpack of 25% of subject´s Body Weight (BW), and walking with the same backpack while wearing the device. Results indicate that wearing the Second Spine significantly reduces the pressure on shoulders and induces smaller deviations from unloaded walking in terms of gait timing and stride length. The activations of the rectus femoris and the gastrocnemius muscles, along with the kinematics of the knee joint, provide indirect evidence that dynamic loads were rigidly transmitted from the shoulder to the waist. We discuss how these preliminary findings might be relevant for the prevention of injuries related to load carriage, and how they set important guidelines for the next generation of the Second Spine.