Positive Health Online

It's amazing what you can carry on your head! The William Mackinnon, a steamer made of steel plates and measuring 104 feet in length, was built in Great Britain and then dismantled and shipped in pieces to Mombasa in East Africa. All the parts – boiler, machinery, etc. – were divided into loads of 50 to 60 pounds' weight and carried on the heads of Africans to Port Florence on the shores of Lake Victoria. Five years and 587 miles of African wilderness later, all the pieces arrived safely at Port Florence where, in 1900, the steamer was rebuilt and successfully launched.

Head carrying is the most economical, graceful and healthy way of transporting objects by human muscle power. This portering technique is still used in Africa, India, Egypt, Melanesia, certain parts of Japan, Indonesia, Asia, and Central and North America. It was still used in Europe until the early part of the 20th century. Even today, in countries such as Portugal or Madeira, off the beaten track you still can come across people carrying things on their heads.

Either bare-headed or with a cloth or little cushion between head and load, sometimes indirectly, in bags or baskets slung from a strap across their head or forehead, people across the world transport all sorts of things in this manner: food, water supplies, fodder, fuel, firewood, laundry, buckets, basins, tools, babies (on the back, but suspended by a strap from the crown of the head) – and let's not forget the odd steamer! There does not seem to be any limit to the variety of objects that can be carried on the human head. The weight involved can be equally impressive. For example, 66 pounds is considered the standard weight for the Sherpas of Nepal, but some, for economic reasons, can manage up to 198 pounds – a risky business, as it is difficult to be surefooted on steep mountain tracks with such a weight hanging from your forehead. In Africa, the women of the Kikuyu and Luo tribes in Kenya can carry on their heads loads that weigh as much as 70% of their body weight.

The way people exhibit such gravity-defying feats with apparent ease demonstrates a great amount of skill. The custom of carrying loads on the head, which, if not overburdened, makes for a stately, upright and graceful carriage, is usually learned at an early age. In some parts of Africa, transporting narrow cylindrical objects, such as bottles, on the head is a specific childhood game. Head-carrying skills can also be a rite of passage: Bishnoi women, for example, are usually married around the age of 13 but don't live with their husbands until they are able to transport two pots of water on their heads from the well to their husband's home without spillage. How great an incentive this is to learn must be open to question!

Head carrying has been studied by some scientists, such as Norman Heglund, a physiologist at the University of Louvain. He wanted to understand how Luo women could carry on their heads loads that weigh almost as much as themselves without apparent tiredness, and why they easily outperformed elite American soldiers who carried the same weight in a rucksack. This advantage is not confined to the Luo but can be demonstrated in anyone who is accustomed to carrying loads directly or indirectly on their head.

People using this method of porterage suffer less breathlessness, less fatigue and less back pain than people carrying loads in any other way.

According to Giovanni Cavagna, studying the mechanics of walking at the University of Milan, it has to do with the way people walk when they have something on the top of their head. Cavagna compares walking to the swinging of a pendulum. A pendulum transforms kinetic energy into potential energy and back again. If it were not for the small amount of energy lost due to friction at its point of attachment and from movement through the air, the conversion of potential energy into kinetic energy in an ideal pendulum would be 100%. A push will transfer sufficient energy into the body of the pendulum to cause it to swing freely for a very long time. During walking, the body behaves like an upside-down pendulum, albeit an imperfect one. Heglund says that we act as only 65% of a perfect pendulum, which means that, for each step we take, 35% of the energy has to be obtained from the calories we burn. Carrying a load on the head seems to trigger an energy-saving mechanism in the gait. For example, when the Luo and Kikuyu women carry 20% of their body weight, they act as more economic pendulums, achieving an average of about 80% efficiency.

In other words, with this weight on their head they use no more energy in walking than is expended without such an encumbrance. The change in their gait is so subtle that it is not visible to the human eye and, unfortunately, the exact mechanism is not yet fully understood.

It would be interesting to see a study of the position of the head in relation to the rest of the body while it is loaded, as this is where I personally believe some clues to this 'anomaly' may be found. I am of the opinion that head carrying has a therapeutic value and I shall explain, in my next article, how it lengthens the spine and encourages an ideal posture, in the hope that some of you will be motivated to give it a try.

Bibliography

Foran Robert W. Transport in Many Lands. Frederick Warne & Co. Ltd. London and New York. 1939.

Samuel Eugenie. How to walk like a pendulum. New Scientist. 13 January 2001.

Kunzig Robert. The physics of walking: falling forward, why humans move like an imperfect pendulum. Discover. 22(7). July 2001.