A comparison of the physiological consequences of head-loading and back-loading for African and European women

Abstract

Aim: to quantify the physiological cost of head-load carriage and to examine the 'free ride' hypothesis for head-load carriage in groups of women differing in their experience of headloading.Method: Twenty four Xhosa women (13 experienced head-loaders (EXP), 11 with no experience of headloading (NON)) attempted to carry loads of up to 70% of body mass (BM) on both their heads and backs whilst walking on a treadmill at a self selected walking speed. Expired air was collected throughout. In a second study nine women, members of the British Territorial Army (TA), carriedsimilar loads, again at a self selected speed.Results: Maximum load carried was greater for the back than the head (54.7±15.1% v 40.8±13.2% BM, P<0.0005). Considering study one, head-loading required a greater oxygen rate than back-loading (10.1±2.6 ml.kgbodymass -1 .min -1 v 8.8±2.3 ml.kgbodymass -1 .min -1 , P=0.043, for loads 10-25%BM) regardless of previous head-loading experience (P=0.333). Percentage changes in oxygen consumption associated with head-loading were greater than the proportional load added in both studies but were smaller than the added load for the lighter loads carried on the back in study 1. Allother physiological variables were consistent with changes in oxygen consumption. Conclusion:The data provides no support for the 'free ride' hypothesis for head-loading although there is some evidence of energy saving mechanisms for back-loading at low speed/load combinations. Investigating the large individual variation in response may help in identifying combinations of factors that contribute to improved economy.2

Assessment of manual load carrying and health status of women farm workers of district Sonipat (Haryana), India

“…But in the present study, contrary to the above study there is a nonsignificant difference between age groups and experience regarding neck pain. This finding is similar to finding of Lloyd et al (2010a), which also concluded that head loading is characterized by significant neck pain and long term habituation does not seems to protect against this but habituated head loaders may have an advantage in terms of balance and stability. All women farm workers in "underweight", "overweight" and "grade-1 obesity" had neck pain whereas only 60 per cent women farm workers from healthy category had pain in their neck.…”

Effects of pole compliance and step frequency on the biomechanics and economy of pole carrying during human walking

“…Other studies that have used a model based on the hypothesis of reducing the CoM of the load to explain energetic savings have also had mixed findings (23,25). What distinguishes our model from these studies is our proposal that pole carriers save energy, not by reducing CoM load displacement relative to a fixed frame of reference (i.e.…”

“…Although some carrying methods (e.g., backpacks) tend to fit this prediction, others vary in relative energetic cost depending on various factors, such as where the load is distributed on the body and how load distribution affects gait (1,18). For example, some African women who carry loads of up to 20% body mass on their heads show no significant increase in energy expenditure (25), though these findings are disputed by some studies (23). Loads carried on the hip (37) or in the hands (35) are relatively more costly than predicted on the basis of added mass.…”

The reliability of the Extra Load Index as a measure of relative load carriage economy

“…h -1 (Harman et al 2001), while school children and individuals in rural areas of developing countries often adopt a slower walking pace of around 3km . h -1 with both light and heavy loads (Singh and Koh, 2009;Lloyd et al 2010b). Although previous research, particularly those on military personnel, have used loads in excess 40 kg (Harman et al 2000), 20 kg was chosen in this study due to the untrained nature of some participants and because similar loads have been frequently used to represent a heavy load in the literature (e.g.…”

“…A number of different exercise intensities have been employed in the load carriage literature with walking speeds ranging from ~ 3 km . h -1 (Maloiy et al 1986;Lloyd et al 2010b) to ~ 6 km . h -1 (Quesada et al 2000) and loads ranging from 10% body mass (Abe et al 2004;Singh and Koh, 2009) to in excess of 50% body mass (Lloyd et al 2010b).…”