Early research on the effect of load carriage focussed on small numbers of soldiers and hikers with the purpose of improving efficiency.  More recently musculoskeletal problems associated with backpack use by school children have become an increasing concern, prompting new research into this area. 

It is well recognised that during their physical maturation children experience periods of accelerated growth.  During these periods, the development of skeletal and soft tissues is rapid.  External forces, such as load carrying, may unduly influence the growth, development and maintenance of alignment of the human body.  Therefore, it seems to follow, that posture affected by backpacks, may make the load carriers more susceptible to spinal injury.  And as children who experience back pains are at increased risk of having back pain as adults a future epidemic of low back pain may be considered likely to occur.

Do Backpacks Affect Posture?

It is intuitive that wearing a backpack will affect the wearer’s posture.  By adding a weight on the back the wearer has to lean forward to ensure their centre of gravity remains over their feet; otherwise they would topple backwards.  The shoulder position moves forward and the head also pokes forwards (Pascoe et al, 1997), and the heavier the load (Grimmer, 2002) and the longer it is carried the greater is the forward change of their immediate posture (Chansirinukor et al 2001).

Whilst there is evidence to show that long term, repeated external forces can influence human posture there is no evidence to show that permanent structural spinal deformity is occurring in school children from backpack or unilateral bag carriage.  The most likely reason for the lack of permanent postural change is that the loads are being carried for short periods - the average time in Western Australia for upper primary and secondary school students being under 15 minutes.

Do Back packs Cause Pain?

Yes, no and maybe.  The current research literature provides mixed results.  However it can be agreed that a proportion of the student population does experience pain and discomfort from carrying a backpack.  Those individuals most at risk are the ones who carry the greatest load.  And this is of concern because episodes of back pain in childhood will lead to episodes of back pain in adulthood

How Much are our Children Carrying?

US research into the bag weights of primary school children found backpack loads represented an average of 8.2% of student body weights but increased significantly with increasing grade level, from 6.2% among kindergarteners to 12.0% among fifth graders.  Twenty-six percent of students carried backpacks that weighed at least 10% of their body weights.  Research on Western Australian high school and upper primary school aged children found the average load carried was 7.5% of body weight, however there were extremes of up to 24.8% of body weight.  In all studies, back pack load weights were found to increase with school level.

What is a Safe Amount for our Children to Carry?

As the strength, size and stature of children vary greatly it has become the norm in the scientific literature to consider backpack load weights as a percentage of the body weight of the carrier.  The research literature produces variable results on what constitutes a reasonable weight for a child to carry, but there are some commonalities. It would seem that a reasonable rule of thumb would be that the maximum load carried be no more than 10-15% of the carrier’s body weight.