Seasonal changes and physiological responses: Their impact on activity, health, exercise and athletic performance

Changes associated with the seasons affect climatic and environmental conditions across the globe. Environmental temperatures, hours of daylight and precipitation vary according to latitude and the prevailing season. Biological and cultural adaptations have enabled humans to inhabit the major climatic regions. Environmental and climatic changes during the annual cycle often force humans to change their social behaviour and the range and amount of physical activity. Such seasonal changes can have a detrimental effect on human health. Seasonal adjustment in human activity and behaviour also influence the physical fitness levels of individuals which alter with the quality of training inputs. The competitive sports calendar determines the circannual variations in training of athletes and their performance peaks. Notwithstanding the seasonal variability observed in physiological variables, the major influences on circannual rhythms appear to be the dimensions of the training programmes employed by athletes. Specific sports are biased towards winter or summer peaks, whereas indoor facilities provide an environment sheltered from the forces of nature and thus promote all-year-round activity. Weather conditions and surface characteristics have consequences for injury risk and the quality of performance. It is concluded that activity and fitness levels are more a function of organisational and external factors than are endogenous circannual rhythms.