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Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in North America and Europe. Happily, the incidence and mortality of CRC have declined by 3.4% and 3.0%, respectively, from 2003 to 2007 in the USA.1 The decline in incidence is attributed to the public health emphasis on the importance of CRC screening and the reduction of behavioural risk factors. For the majority of people who do not use tobacco and alcohol, the most important determinants of CRC risk factors are weight control, dietary choice and level of physical activity. A number of investigations have demonstrated the benefit of exercise on CRC prevention, and guidelines released by governmental and non-governmental organisations also emphasise the importance of regular exercise for decreasing CRC incidence.
Although the correlation between exercise and CRC prevention is conclusive, the molecular mechanism for the protective effect of exercise remains largely unresolved. Epidemiological and experimental studies have proposed several possible biological mechanisms to explain the exercise–malignancy relationship, including regulation of metabolic activity, production of sex hormones, alterations of antioxidant enzymes and growth factors, body weight control, and alteration of immune system.2 Recent studies have shown interleukin-6 (IL-6), IL-8, IL-15, brain-derived neurotrophic factor and leukaemia inhibitory factor to be exercise-induced myokines that mediate several biological processes.3 However, none of these …