Front packs: is 15% safe? Evaluation of the effect of different front pack loads on 3D back shape and posture in asymptomatic young adults

Abstract

Introduction: Load carriage is a significant factor in the aetiology of back pain. Front load carriage in particular, is a significant problem in obese individuals, as well as pre and post pregnancy in women. Further, carrying a frontpack is routinely used within some industries such as agriculture and construction. Whilst the focus of much of the literature is on backpacks, little is known on the effects of a front pack. The load carriage recommended for children found in the literature is 10% body weight (Moore et al, 2006). However load limits for adults are controversial ranging from 10-20% body weight. The objective of this study was to evaluate the effect of a 10%, 15% and 20% frontload on standing backshape and posture in asymptomatic young adults. Materials and methods: The Integrated Shape Imaging System 2 (ISIS 2) was used in this study. This is a low cost automated system, that measures the three-dimensional shape of the back in patients with scoliosis and is described in detail elsewhere (Berryman et al, 2008). The study involved twenty-five students from the School of Health and Social care, Teesside University. A repeated measures design was used to record the effects of four conditions using a front pack: No load [reference], 10% body weight, 15% body weight and 20% body weight on the subjects standing posture for five minutes, using the ISIS 2. All of the conditions were randomised to offset any order effects. Results: The results of the present study showed that in the sagittal plane, the mean overall lordosis and kyphosis angles increased with increasing load (p<0.05). Back length and extension also increased significantly from the no load position to the 20% (p<0.05) loaded posture. No statistically significant differences however were found in each of the following variables (p>0.05); lateral asymmetry (curvature) in the thoracic and lumbar spine and in the horizontal Max Skin Angle variable. Discussion: The use of a front packs results in a more upright posture. These findings are similar to those of studies conducted previously, using a front pack. However as expected the results also demonstrate changes in the opposite direction to those found in studies involving backpacks. Conclusion: It was concluded that increasing the load to greater than 10% body weight, whilst using a front pack, has a significant effect on an individuals standing posture. The results also suggest that overloading frontpacks may cause significant injuries to the back and surrounding musculoskeletal structures.