Division of Sport and Exercise Sciences, University of Abertay Dundee, Dundee, DD1 1HG, UK.
Eur J Appl Physiol. 2010 Jul;109(4):607-16. doi: 10.1007/s00421-010-1395-9. Epub 2010 Feb 26.
The aim is 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 head-loading. Twenty-four Xhosa women [13 experienced head-loaders (EXP), 11 with no experience of head-loading (NON)] attempted to carry loads of up to 70% of body mass 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, carried similar loads, again at a self-selected speed. Maximum load carried was greater for the back than the head (54.7 +/- 15.1 vs. 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 vs. 8.8 +/- 2.3 ml kg bodymass(-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. All other physiological variables were consistent with changes in oxygen consumption. 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.
目的是量化头部负重的生理成本，并检验头部负重的“搭便车”假说，该假说针对的是经历不同的女性群体。24 名科萨妇女[13 名有头部负重经验（EXP），11 名无头部负重经验（NON）]在跑步机上以自选速度行走时，尝试在头部和背部承载高达 70%体重的负荷。在此过程中收集呼出的空气。在第二项研究中，九名英国领土军的女性成员以类似的速度承载类似的负荷。背部承载的最大负荷大于头部（54.7 +/- 15.1 与 40.8 +/- 13.2% BM，P < 0.0005）。考虑到第一项研究，头部负重比背部负重需要更高的氧气消耗率（10.1 +/- 2.6 与 8.8 +/- 2.3 ml kg bodymass(-1) min(-1)，P = 0.043，对于 10-25% BM 的负荷），无论之前是否有头部负重经验（P = 0.333）。与头部负重相关的氧气消耗百分比变化大于两项研究中附加负荷的比例，但小于在第一项研究中在背部承载较轻负荷时的附加负荷。所有其他生理变量与氧气消耗的变化一致。这些数据不支持头部负重的“搭便车”假说，尽管在低速/低负荷组合下，背部负重存在节能机制的证据。研究个体对该机制的反应差异可能有助于确定有助于提高效率的因素组合。
