Investigating the association between recreational physical activity, sedentary behaviour, resistance training and the risk of colon and rectal cancers

[Truncated abstract] The primary aim of this thesis was to investigate the association between physical activity and the risk of colon and rectal cancers. There has been a substantial amount of prior research done in this area, and reviews of this research have concluded that there is convincing evidence that physical activity reduces the risk of colon cancer, although the evidence is less convincing for rectal cancer. However, there are several aspects of the relationship between physical activity and colon and rectal cancers that remain unclear. These issues include: the timing and intensity of physical activity required to optimally reduce risk; whether sedentary behaviour has an independent influence on the risk of colon and rectal cancers; whether non-aerobic physical activity (such as resistance/strength training) is independently associated with the risk of colon and rectal cancers; and whether physical activity has a different effect on the risk of proximal colon and distal colon cancers. Each of these issues, as well as some methodological issues concerning measurement of lifetime physical activity, has been investigated in this thesis.