INTRODUCTION

The tropical habitat currently faces strong pressures. In many parts of Africa, the current growth rate for human populations is 4.5–5.0% per annum, compared with the world average of 1.7%. While there remains some disagreement on minimal nutritional requirements (Rivers & Payne, 1982; Weymes, 1982), the expanding deserts of the sub-Saharan poverty belt threaten starvation to many peoples of this region. At the same time, large parts of the African continent have very few inhabitants. In the “Decade of the Tropics” much thus depends on human ability to exploit the African habitat, producing a surplus of food that can nourish rapidly expanding cities.

One important determinant of the ability to colonize any harsh environment is the individual's physiological working capacity (Harrison & Walsh, 1974; Shephard, 1978), the “ability to perform muscular work satisfactorily” (Andersen et al, 1971). In this review, particular attention will be paid to developments since completion of the International Biological Programme (LB.P., Worthington, 1978). The changing nature of work capacity will be discussed in a tropical context, along with issues such as sampling bias, technical problems of measurement in a hot environment, and procedures for allocating variance between constitution and environment. The effect of changes in body size, nutrition and health will also be considered briefly.

THE CHANGING NATURE OF WORK CAPACITY

The physiological characteristics appropriate to successful colonization of a given habitat depend on (i) population pressures, (ii) the amount of physical work necessary for survival, and (iii) available technology (Breymeyer & Van Dyne, 1979).