Simeon Eh Davies

Subjective perceptions of load carriage on the head and back in Xhosa women

The purpose of this study was to compare the subjective perceptual responses to both head-loading and back-loading in a group of Xhosa women. Thirty two women were divided into three groups based on their experience of head-loading and walked on a treadmill on two occasions, head-loading and back-loading, at a self selected walking speed for 4 min with a variety of loads until pain or discomfort caused the test to be terminated or a load of 70% body mass was successfully carried. After each workload there was a 1 min rest period during which the women indicated feelings of pain or discomfort in particular areas of the body via visual analogue scales. At the end of each test the women were asked to complete further questionnaires relating to pain and discomfort and on completion of the second test were also asked to compare the two loading conditions. Finally the women were interviewed to establish their history of load carriage and associated pain and discomfort. The data indicate that whilst back-loading was generally associated with more areas of discomfort than head-loading, the pain and discomfort in the neck associated with head-loading was the predominant factor in the termination of tests and that this was independent of head-loading experience. This early termination meant that, on average, the women could carry greater loads on their backs than on their heads. The study suggests that further work needs to be carried out to establish viable alternatives to head-loading for rural dwellers in Africa.

The energetics of walking on sand and grass at various speeds

This study investigated the energetics of walking on sand and grass. Fourteen adult males, participated in the study. Participants had a mean age of 34.6 years old, 72.6 kg in mass and 172.5 cm in stature, who walked at 3, 4, 5, 6 and 7 km per h on sand and grass surfaces. Physiological measures included heart rate, O2 uptake, CO2 exhalation, ventilation and relative O2 uptake using a MetaMax Ergospirometer. Speed was controlled in a methodology similar to the ‘Multistage 20-m Shuttle Run Test’. Data were collected during physiological steady rate at each determined speed. A minimum of 2 h rest was enforced between randomized conditions. Results indicate that there was a significant increase (p < 0.01) in all measured physiological indices indicative of energy expenditure when walking on sand compared to grass at 3–7 km per h, with the greatest disparity between the surfaces (ratio = 1.63) in relative O2 consumption at 5 km per h.

A kinetic comparison of back-loading and head-loading in Xhosa women

The purpose of this study was to compare the kinetic responses associated with ground reaction force measurements to both head-loading and back-loading in a group of Xhosa women. Altogether, 16 women were divided into two groups based on their experience of head-loading. They walked over a force plate in three conditions: unloaded or carrying 20 kg in either a backpack or on their head. The most striking finding was that there was no difference in kinetic response to head-loading as a consequence of previous experience. Considering the differences between the load carriage methods, most changes were consistent with increasing load. Head-loading was, however, associated with a shorter contact time, smaller thrust maximum and greater vertical force minimum than back-loading. Both loading conditions differed from unloaded walking for a number of temporal variables associated with the ground contact phase, e.g. vertical impact peak was delayed whilst vertical thrust maximum occurred earlier. Statement of Relevance: Consideration of the kinetics of head and back load carriage in African women is important from a health and safety perspective, providing an understanding of the mechanical adaptations associated with both forms of load carriage for a group of people for whom such load carriage is a daily necessity.

A comparison of economy and sagittal plane trunk movements among back-, back/front- and head-loading

Abstract It has been suggested that freedom of movement in the trunk could influence load carriage economy. This study aimed to compare the economy and sagittal plane trunk movements associated with three load carriage methods that constrain posture differently. Eighteen females walked at 3 km.h−1 with loads of 0, 3, 6, 9, 12, 15 and 20 kg carried on the back, back/front and head. Load carriage economy was assessed using the Extra Load Index (ELI). Change in sagittal plane trunk forward lean and trunk angle excursion from unloaded to loaded walking were assessed. Results show no difference in economy between methods (p = .483), despite differences in the change in trunk forward lean (p = .001) and trunk angle excursion (p = .021) from unloaded to loaded walking. We conclude that economy is not different among the three methods of load carriage, despite significant differences in sagittal plane trunk movements. Practitioner summary: This article shows, based on mean data, that there is no difference in economy among back, back/front and head-loading, despite differences in trunk movement. It is possible a combination of factors align to influence individual economy, rather than a single set of factors, applicable to all individuals for each method.