Shephard R J
School of Physical and Health Education, University of Toronto, Ontario, Canada.
Sports Med. 1993 Apr;15(4):258-80. doi: 10.2165/00007256-199315040-00004.
Physical activity potentially encourages a healthy lifestyle and it could have a more direct preventive effect on certain forms of carcinogenesis (for instance, by speeding gastrointestinal transit, or by moderating sex hormone levels). However, there are also potential negative effects, particularly an excessive exposure to ultraviolet light in certain water sports. The many types of neoplasm and the equally varied sources of physical activity militate against finding any simple relationship between the risk of malignancy and the individual's physical activity history. Nevertheless, evidence that physical activity protects against certain forms of cancer can be deduced from studies of experimental animals, former athletes, people employed in active occupations, and those with an active recreational lifestyle. Many occupational surveys and a number of studies of recreational activity show an association between sedentary living and a risk of colon cancer, both in men and in women. Moreover, an application of Bradford Hill's criteria gives some support to the causal nature of the association. More limited data suggest that a history of active leisure is associated with a reduced risk of all-cause cancer and in women of breast and reproductive system cancers. The last observation must still be reconciled with an apparent increase in the risk of prostatic cancer in active men. Since moderate exercise elevates mood and helps to conserve lean tissue, it may finally be a helpful component of treatment after a neoplasm has been diagnosed.
体育活动可能会促进健康的生活方式，并且可能对某些致癌过程具有更直接的预防作用（例如，通过加快胃肠蠕动或调节性激素水平）。然而，也存在潜在的负面影响，特别是在某些水上运动中过度暴露于紫外线下。肿瘤的类型繁多，体育活动的来源也同样多样，这使得难以找到恶性肿瘤风险与个人体育活动史之间的任何简单关系。尽管如此，从对实验动物、前运动员、从事体力活动职业的人以及具有积极休闲生活方式的人的研究中，可以推断出体育活动对某些类型癌症具有预防作用的证据。许多职业调查以及一些关于休闲活动的研究表明，久坐不动的生活方式与男性和女性患结肠癌的风险之间存在关联。此外，应用布拉德福德·希尔标准为这种关联的因果性质提供了一些支持。更有限的数据表明，积极休闲的经历与全因癌症风险降低以及女性患乳腺癌和生殖系统癌症的风险降低有关。最后这一观察结果仍必须与积极运动的男性患前列腺癌风险明显增加的情况相协调。由于适度运动能提升情绪并有助于保留瘦组织，它最终可能成为肿瘤被诊断后的一种有益治疗成分。
