Independently Tested for Your Health

INDEPENDENTLY TESTED BY CENTRE FOR ALLIED HEALTH EVIDENCE
University of South Australia
Project Directors: Associated Professors Karen Grimmer & Mr. Steve Milanese

This study provides evidence regarding the usefulness of the Drag Bag in protecting spinal health.   The research questions were:

Testing comprised three phases: laboratory assessment, ergonomic assessment and a field study.   

Side-view photographs were taken of body posture, using usual marker positions.    From the x,y coordinates digitised from these pictures, postural change in the horizontal direction was measured between different carrying conditions and backpacks, and within-subject comparisons made.       

There were consistent findings for all but one of the children, and for six of the adults, in the way they responded to the Drag Bag, compared with ‘unloaded’ posture.   

There was a linear response of increasing net postural deviation from ‘unloaded’ for loads of the empty bag, 5% and 10% of body weight. However, the Drag Bag seems to perform better with higher loads in it, as it produces the same amount of postural deviation at higher loads as it does at lower loads. There seems to be a threshold effect at about 10% body weight, where the true value of the bag becomes obvious under its backpack carrying performance. Carrying a weight in the computer pocket seems also to be more posturally efficient than carrying the same weight in the body of the backpack .  

This finding is of particular interest, when considering the variability in ‘unloaded’ posture in the children in the study. Thus it seems that wearing Drag Bag on the back corrects posture of young people.

All but one participant liked the Drag Bag design, including the fabric, strap width and positioning, compartment design and features (such as lunchbox, rain cover etc).  

Preliminary testing of trolley bag version of the Drag Bag around the laboratory and the immediate university environment (up and down stairs, in and out of lifts, on carpet, tiles, gravel, concrete) brought favourable reactions from everyone, with the friction-free wheel design bringing most approval .

All subjects commented on the comfort of the Drag Bag when worn as a backpack, saying that the strap width suited their body shape, the backpack sat comfortably on their backs (and in some instances subjects noted that they seemed to stand better with the backpack on). They didn’t notice any increase in discomfort when increasing weights were placed into the backpack during testing.

Drag Bag performs well under laboratory conditions for most body types, and for both genders over a range of ages.   When it is unloaded, it significantly changes ‘unloaded’ posture, but then so have every bag that we have tested. It seems to perform better under heavier weights, when carried in the body of the backpack, and in the computer pocket.   It seems that carrying Drag   Bag on the back, as in a conventional backpack arrangement, does not put the spine under abnormal horizontal perturbations, and thus it can be deemed to be posturally safe for adult and child wearers.  

The Drag Bag offers a well designed piece of equipment which works well as a backpack and as a trolley bag under usual conditions.   It seems to handle heavier weights well in its backpack version, and its ease of locomotion as a trolley bag suggests that this is also an efficient way of transporting heavy loads .

Drag Bag was tested for one week under usual load carrying and transport conditions by six subjects (three children and three adults) (representing 6 weeks total of testing).   The good things about the bag were commonly identified as being:

All subjects liked the trolley-bag feature of the Drag Bag – the trolley handle seemed to be at an appropriate height for all subjects (irrespective of their physical size), the wheels travelled over all required terrain, it was very energy efficient to drag heavy loads and easy to manoeuvre the trolley bag in all situations.