Given the decline in the amount of physical activity that most people have to perform in
work duties (as illustrated by the example of the Amish community lifestyle in Box 1.1), and the increase in motorised transport, a great deal of the physical activity that has become nec-essary for health must be freely chosen in leisure time or consciously integrated into one’s normal daily routine. This, in itself, justifies the increasing importance of studying psycho-logical processes, such as motivation and decision-making, in physical activity, alongside other influences such as social and environmental factors.