Leg problems in fast-growing chickens (broilers) are a major health problem in commercial conditions. They seem partly due to lack of physical exercise. Several factors can modify broiler activity. Early body weight is negatively correlated with level of activity: the fighter the birds are, the more active they are. Increasing environmental complexity (barriers, toys, sand, new objects) can stimulate temporarily activity, but this is not sufficient to eliminate leg problems. Introducing complexity in diet distribution (shape, feeding schedule, food composition) seems to be much more efficient to stimulate exploratory behavior, but it is often related to a slightly decreased bodyweight. The induced changes in level of activity allow to decrease leg problems. Introducing changes in diet distribution stimulates activity and could be an interesting way to prevent from leg problems.