Physical activity in rural South Africa--are current surveillance instruments yielding valid results?

To the Editor: A recent important study1 addressing the prevalence of cardiovascular risk factors in a rural African population, reports that ‘... most participants followed a physically inactive lifestyle’. The validity of their findings is difficult to evaluate as the study provides little information regarding the physical activity questionnaire that was used. Questionnaire validity is relevant because rural women can carry a heavy work burden, particularly with regard to household and yard work, and aspects of farming.2 Since few – if any – females in the Dikgale site participate in sport or exercise, the physical activity questionnaire could display a ‘floor’ effect, i.e. below a certain threshold, important healthcontributing physical activity behaviours are not probed.