Functional measurements

8.10. There is one final type of measurement of great potential value: measurement of functional capacity, an obvious example being the level of physical activity. Thomson(15), describing trials organized in the United Kingdom by Boyd Orr and others in the 1920s to test the effect of giving milk to school-children, wrote: "Acceleration of growth was confirmed and clinical examination of the children and reports from teachers suggested that the milk-fed children had improved in general condition and became much more alert and more boisterous and difficult to control than others." The difference in height growth between supplemented and unsupplemented children in this trial was 6 mm/year, but the difference in activity was likely to have been of much greater importance.

A reduced level of activity in children consuming inadequate but not disastrously low amounts of dietary energy has also been reported among rural children living in Uganda (16). Studies at INCAP in Guatemala (17) have likewise demonstrated that energy intake of pre-school children can be reduced from 90 to 80 kcal/kg without affecting nitrogen balance or growth, but this is only possible because of a reduction in energy expenditure.

Activity is an even more relevant functional parameter for pregnant and lactating women, as they represent an important component of the labouring work-force, particularly in rural areas of the developing world. As discussed in section 1.17, studies in Sri Lanka have demonstrated that iron supplementation enables work output to be increased. Investigations into work capacity and energy output need to be designed with imagination and flexibility; however, it is possible for a woman to complete the same task with a minimum of extraneous effort or with more joie de vivre. It is not unreasonable to suggest that the latter style of working provides a greater sense of well-being and general happiness. In the Gambia the unanimous first reason given by pregnant and lactating mothers for the popularity of the biscuit supplement (see section 3.26) was that it gave them more "power" for work. Since there is, as yet, no evidence that they were doing more actual work, it can only be concluded that this statement means the mothers were better able to work well within their capacity rather than at the extreme limit.

It is quite apparent that the use of functional tests is a subject that merits a much greater research input. Quite apart from their intrinsic physiological interest, it would enable the merits of nutritional intervention programmes to be translated into terms relevant to national development planning. They might be taken more seriously by politicians and government officials than would more medical and biochemical measurements whose significance is less obvious.