坚持运动真的能预防癌症？
One of the most important benefits of exercise is in how it reduces our risk of developing a number of types of cancer — especially colorectal cancer, which according to some estimates is the malignancy most influenced by physical activity.
运动最重要的好处之一就是降低我们患多种癌症的风险，尤其是直肠癌，据一些研究，在恶性肿瘤中，运动对直肠癌最有效。
But how workouts guard against colon cancer remains largely unknown. Physical activity speeds the movement of waste through the intestines, as anyone who has had to hunt for a bathroom during a workout knows.
但是运动如何能预防直肠癌仍然是个未知数。在运动时你会发现上厕所的频率更高了，因为运动加速了排泄物在肠道中的运动。
But this does not seem to fully account for the protective effects of exercise. Instead, a small study published in February in The Journal of Physiology suggests we should also look to changes in our bloodstream after exercise.
但这似乎不能完全解释运动的预防作用。不过，2月份在《生理学杂志》上发表的一项小型研究建议我们可以更多地关注运动后血液的变化。
The new study began with scientists at the University of Queensland in Brisbane, Australia, and other institutions recruiting 20 men who had survived colon cancer. (Women were excluded because menstruation might have affected results.)
这项新的研究由澳大利亚昆士兰大学和其他机构的科学家发起，他们招募了20名直肠癌患者。（女性被排除在外，因为月经可能会影响结果。）
The scientists asked 10 of the men to start working out strenuously three times a week: pedaling a stationary bicycle hard for four minutes, resting for three, and repeating that sequence three more times. They trained for a month and then, a few days after completing the program, rested quietly while researchers drew blood.
科学家们要求10名男性一周做三次剧烈运动：用力踩静止单车四分钟，休息三分钟，再重复三次。训练了一个月之后，十个人完成了运动计划。几天后，研究人员在他们休息时进行抽血。
The other 10 men completed the same 4 x 4 interval session, but only once. The researchers drew their blood before, immediately following and an additional two hours after that lone workout. 另外10名男性完成了同样的4×4间歇训练，但只做了一次。研究人员在这项单独的运动之前、完成之后以及完成两个小时之后抽取了他们的血液。
The scientists then carefully added a tiny amount of fluid from the men’s blood to petri dishes containing human colon-cancer tumor cells often used to study cancer growth. At several points during the subsequent 72 hours, the researchers counted the numbers of cells in each dish. They soon saw substantial differences.
然后，科学家们小心地在含有人类结肠癌肿瘤细胞（通常用于研究癌细胞生长）的培养皿中加入少量男性血液中的液体。在接下来的72小时里，研究人员计算了每个培养皿中细胞的数量。他们很快就看到了实质性的差异。
In the dishes containing fluid taken from the men immediately after a single workout, the scientists counted far fewer cancer cells than in those awash in fluid drawn two hours after exercise. There was no similar decline in the dishes from the men who had trained for a month. In effect, something about the blood drawn immediately after the workout was slowing the growth of cancer cells.
相比运动后2小时才抽取的血液，科学家发现在将运动后立即取出的血液加入培养皿后癌细胞会大量减少，而运动后一个月的血液也无法达到这种效果。实际上，锻炼后立即抽取的血液会减缓癌细胞的生长。
The researchers think they may have identified that something in subsequent analyses of the men’s blood. They found a large increase in molecules involved in inflammation immediately after exercise. Inflammation can slow cell growth and reproduction.
研究人员认为他们可能在随后的血液分析中发现了一些东西。他们发现运动后，诱发炎症的分子会急速增加，而炎症可以减缓细胞生长与繁殖。
So a transitory increase in inflammatory markers after exercise might be helping to jam the proliferation of tumor cells, says Tina Skinner, a physiologist who was the senior author of the study.
这项研究的资深作者、生理学家蒂娜·斯金纳说：“因此，运动后炎症分子的短暂增加可能有助于癌症细胞的繁殖。”
The implications of these results are both cheering and cautionary. The changes in exercisers’ blood were potent but “transient,” Skinner says.
这些结果的寓意既让人振奋又令人警觉。斯金纳说，运动者血液中的变化对癌症是强有力的，但同时也是“短暂的”。
So activities would have to be repeated to provide any continuing protection, and it remains unclear how intense or prolonged that exercise ideally would need to be, or if the effects extend equally to fighting other types of cancer.
因此，必须坚持运动以提供持续的癌症预防效果，目前尚不清楚理想情况下运动的强度需要有多大、持续时间需要多长，或者其影响是否对其他癌症也有效。
But even so, Skinner says, “We would recommend that exercise be embedded as part of standard practice for people living with and beyond cancer.”
尽管如此，斯金纳说，“我们还是建议癌症患者和预防癌症人群将运动作为健康生活实践的一部分。