Shephard R J, Futcher R
Faculty of Physical Education and Health, University of Toronto, ON.
Crit Rev Oncog. 1997;8(2-3):219-72. doi: 10.1615/critrevoncog.v8.i2-3.40.
A series of meta-analyses have examined relationships between regular physical activity and susceptibility to various forms of cancer. Regular physical activity protects animals against cancer from a variety of sources: subcutaneous, intraperitoneal or intragastric carcinogens, intravenous infusion of tumor cells, or tumor implantation. In humans, regular exercise reduces susceptibility to all-cause cancer, colonic adenomas, colon but not rectal cancers, breast cancers, uterine tumors, prostate and testicular tumors, and possibly lung cancers. At most tumor sites, the average response of women is similar to that of men, but because of a limited number of studies, the effect in women is commonly nonsignificant. The relative effects of occupational and leisure activity are generally similar, an observation that suggests that the optimum response of cancer defense mechanisms is obtained from moderate levels of energy expenditure. In general, the data show a dose-response relationship, the risk of a sedentary lifestyle approximately doubling on passing from a moderate to a low level of habitual physical activity. To date, the findings have not demonstrated the postulated j-shaped relationship, but the cross-sectional comparison of low vs. high levels of leisure activity suggests that the adoption of an active lifestyle could reduce all-cause cancer rates by as much as 46%.
一系列的荟萃分析研究了规律体育活动与对各种癌症易感性之间的关系。规律体育活动能保护动物抵御来自多种途径的癌症：皮下、腹腔内或胃内致癌物、静脉注射肿瘤细胞或肿瘤植入。在人类中，规律运动可降低对各种原因导致的癌症、结肠腺瘤、结肠癌（而非直肠癌）、乳腺癌、子宫肿瘤、前列腺和睾丸肿瘤以及可能的肺癌的易感性。在大多数肿瘤部位，女性的平均反应与男性相似，但由于研究数量有限，女性中的效果通常不显著。职业活动和休闲活动的相对影响通常相似，这一观察结果表明，癌症防御机制的最佳反应是通过适度的能量消耗获得的。总体而言，数据显示出剂量反应关系，从适度的习惯性体育活动水平降至低水平时，久坐不动生活方式的风险大约会翻倍。迄今为止，研究结果尚未证实假定的J形关系，但低水平与高水平休闲活动的横断面比较表明，采用积极的生活方式可将各种原因导致的癌症发病率降低多达46%。
