CHAPTER 25 ACTIVITY PATTERNS AND ENERGY EXPENDITURE IN CAMEROONIAN TROPICAL FOREST POPULATIONS Patrick PASQUET and Georgius l.A. KOPPERT INTRODUCTION Physical activity is the main component of energy expenditure in subsist- ence societies, notably in the African rain forest. Activity patterns are socially determined. They are the place of integration of most behavioural responses to scarcity (Ferro-Luzzi, 1988) or to the increase of nutritional needs such as, for instance, seasonal availability of food or the increase of biological needs related to reproduction. Comprehensive data on activity patterns and energy expenditure are fragmentary for the humid tropics, and especially in African rain forest populations. Numerous field studies focused on anthropological, ecological or developmental issues have contributed to our knowledge of gross pat- terns of activity and work load, using time allocation techniques (Gross, 1984). Very few studies, however, have reported accurate estimates of both time expenditure and activity metabolic rates which are needed for a good understanding of human nutritional requirements, although one can cite the energy balance studies conducted by Montgomery and Johnson (1977) among the Machiguenga horticulturalists of Peru and by Dufour (1984, 1992) among the Tukanoan Indians of Colombia. The purpose of this contribution is (1) to describe patterns of activity and habitual energy expenditure in two Cameroonian rain forest communities living at the level of subsistence - the fishermen-agriculturalist Yassa and the hunter-agriculturalist Mvae; (2) to compare these findings with estimates inother Cameroonian forest populations who have adopted a different strat- egy of production: cacao planters; and (3) to compare the estimates of energy expenditure to the worldwide variation. The ecological setting of the studied populations is presented by Koppert cl al. (1993, this volume), with data on food consumption; their health status and socio-cultural background are also discussed, respectively by Frornent et al. (1993, this volume) and by Garine (1993, this volume). 311