Metabolic and kinematic responses of African women headload carriers under controlled conditions of load and speed

Abstract

Recent investigations have argued for the metabolic efficiency of headloading as a mode of load-carriage, and have included proposals of an energetic 'free-ride' for loads under 20% bodymass. Our own energy-cost analyses on laboratory-habituated African women occupational headloaders is used to evaluate the free-ride hypothesis, but more especially to throw new light on the kinematics of foot-floor contact patterns. Under headloading there is a tendency for the impact-receiving mechanisms of the foot to be less effective. However, a delayed heel-rise later in the step increases stability of support by reducing the duration of forefoot-only contact. Plantar thrust under headloading has a relatively longer duration, which may have force-velocity implications for the propulsive musculature.

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

“…The tendency for difference between the groups (P=0.069) and the lack of interaction between group and loading method (P=0.333) would suggest that, whilst the EXP group were generally more efficient load carriers than the NON group they were also more efficient whilst backloading than head-loading. Again this was a somewhat unexpected finding and stands in contrast to the seminal works in this area (Maloiy et al, 1986;Charteris et al, 1989a, Charteris et al, 1989b. One possible explanation for this is that the participants in these early studies were considerably more experienced headloaders than those used here.…”

“…One possible explanation for this is that the participants in these early studies were considerably more experienced headloaders than those used here. It is certainly the case that the six participants in the studies by Charteris et al (1989aCharteris et al ( , 1989b were older and more experienced, age 33.7 ± 9.4 years and head-loading experience 22.5 ± 8.9 years, than the participants in the EXP group in the present study, who had at least ten years head-loading experience and were aged 22.5 ± 2.1. Maloiy et al (1986) provide no data in relation to age or experience, although the participants were characterised as experienced head-loaders.…”

Effects of load carriage, load position, and walking speed on energy cost of walking

“…However, some researchers revealed that African women can carry an extra-heavy load that amounts to 40% of the body mass on their head (Maloiy et al, 1986;Charteris et al, 1989b). It was reported that the metabolic cost while walking with loads did not necessarily increase if the load was less than 20% of the subject's body mass (Charteris et al, 1989a). These authors termed the phenomenon 'free-ride' (Charteris et al, 1989b), and referred to free-ride as carrying loads on the head.…”

Health impacts of pedestrian head-loading: A review of the evidence with particular reference to women and children in sub-Saharan Africa

“…Maloiy et al suggest (p.669) that 'some anatomical change has occurred, as a result of carrying large loads since childhood, which allows these women to support small loads using non-metabolizing structural elements', but this conclusion is based on studies with just five women (three head-loading Luo; two head-strap/back-loading Kikuyu). Charteris et al (1989), however, examined treadmill data for 150 Xhosa women agricultural labourers (randomly selected and from a wide age-range) and confirmed that the energy expended per unit of load carried was constant, at least until 20% body mass loads were being moved. that it is possible to select a subset of women from their own data set who achieve 9 remarkable levels of energy economy and argue that this 'is not altogether unexpected but suggests that the "free ride" hypothesis is not a generalizable finding, when tested with larger more representative samples of African women ' (2010c: 614).…”