Scientific and medical testing

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The discomfort experienced when carrying a load in a backpack is a serious problem for students, travellers, workers, military personnel, and those engaging in outdoor pursuits.

Our aim was to carry out a scientific and medical pre-study to break down the various strains that a backpack can exert upon the body, and its impact on posture, before proceeding with any business venture.

Movement analysis systems using force plates were employed to carry out inverse dynamic analysis, in order to assess how wearing a backpack influences kinematics and joint momentum during walking, for example. A number of existing algorithms had to be adapted to fit our purpose, while the measurement of pressure exerted by the pack on the back was made possible using a pressure sensor pad on a number of test subjects.

When walking, the thorax acts as a support base that’s fixed in space, and can absorb the energy from pelvic rotation in order to redistribute it, like a spring. In addition, it helps maintain head stability, and therefore a horizontal field of vision. This is where the swinging of the arms comes into play: they act to balance the thorax and enable it to remain stable. If the movement of the arms is restricted, a whole set of muscles in the back are needed in order to stabilise the thorax, which requires more energy to be used.


In order to walk efficiently

  • the rotation of the pelvis must be preserved,
  • the thorax needs to be stable,
  • the shoulders must be free, in order to enable the arms to swing.

Backpack without Gravipack®

  • inertia momentum acts to destabilise the thorax,
  • weight is mostly applied to the shoulders, which leads to discomfort and limits arm swing,
  • pelvic rotation is reduced

Ordinary backpack with Gravipack®

  • 30% of shoulder weight is transferred to the pelvis. Shoulders are freer, less discomfort, less limiting for the arms.
  • pelvic rotation is limited, with the belt acting as an immobilizing restraint.

Here’s what you need to know

A backpack that’s too heavy causes the body to bend forward, which results in rounded shoulders; in this position, muscles and ligaments are no longer able to do their job of holding the body upright, which leads to pain not only in the neck and shoulders, but also in the lumbar area, the hips and even in the knees.

Thanks to its innovative technology, Gravipack® reverses this phenomenon, enabling you to keep your back straight and improve your overall posture: your field of vision stays flat, your body has greater freedom of movement, and the arm swing that’s essential to your gait happens more naturally. This helps you avoid migraines and pain at the end of the day, as well as scoliosis in young people.
A biomechanical pre-study with movement analysis, using body sensors with the product, provided hard data to back up the feeling of lightness reported by users – which was even more positive than we had hoped for!


This also determines the characteristics of our Gravipack® device:

  • shoulders are freed up, arm swing is maintained,
  • thorax is stable,
  • External framework around the thorax (rigid loops and two belts: upper and lower thorax), which use the bag’s weight to ensure greater stability of the body’s architecture
  • bag’s inertia momentum is more in step,
  • weight of the backpack is spread along the sides.

*Université Lyon 1 Biomechanical Study and Movement Analysis, IFSTTAR laboratory