Health is not a clearly defined notion, although we all feel we know what it is. This vagueness derives from the subjective nature of health. Health means fitness to live, with a feeling of well-being, and all these elements-'fitness', 'feeling' and 'well-being'-are subjective. While health escapes precise measurement, its description requires a definite point of reference which must be linked to the environment. Health reflects the relationship between an organism and its environment in both time and space. This chapter discusses four main interrelated problems: how to define health in terms of environmental criteria; how to measure health using positive indices (such as body build and physical fitness) in relation to those values from local populations, which have been moulded by the environment; limitations of negative indices of health (morbidity and mortality); and how the relationships between human populations and the environment change in the contemporary world, with the effects of modern civilizations and new pathological phenomena.
Health is not a clearly defined notion although we all feel we know what it is. This vagueness derives from the subjective nature of health. While health escapes precise measurement, its description requires a definite point of reference, which could be found in the environment.
Health could be understood as a 'certain' psycho-physical condition of humans determined by a 'proper' structure of the organism as well as a result of a 'dynamic balance' between the organism and its environment (homeorhesis).
Dynamic balance, or homeorhesis, is a developmental homeostasis over the time of ontogenetic development, related to the age of the subject and environmental conditions. It is changing (dynamic) homeostasis. The words 'certain' and 'proper' are indicative of how relative the evaluations may be.
Health is a vector, showing a range from good to bad health. This meaning of health could be applied, with slight modifications, to entire populations. Health and its symptoms vary substantially and dynamically with time and space. The