Can You Exercise Too Much?

By John Swartzberg

Most of us wish we exercised more.After all, fewer than half of us get the recommended amount of physical activity, and we know it. But is it possible to get too much of a good thing?

[2] It turns out that the answer is yes. Exercise provides many health benefits, but at some point working out too hard or too long increases the risk of injury and other adverse effects.That usually only happens with intense exercise, like training for marathons or endurance activities. Such challenging activities are perfectly fine, maybe even laudable endeavors, but if you’re looking for optimal health benefits, research suggests that more moderate workouts are generally the way to go.

[3] True, it’s a problem relatively few Americans need to worry about, since inactivity is far more common and also more harmful. And not all the research on “extreme” exercise has found increased risks—but overdoing exercise can be a problem.

大多数人都希望能多运动，毕竟我们当中能达到推荐运动量的人还不足一半，大家都清楚这一点。但好东西过了头会不会适得其反呢？

[2]答案是肯定的。运动于健康大有裨益，但如果运动太剧烈或运动时间过长，则会增加受伤风险，产生负面效果。一般来说这种情况只出现在剧烈运动后，比如马拉松训练或者耐力运动。此类有挑战性的运动固然不错，甚或值得提倡，但研究认为，要达到最佳锻炼效果，还是要选择更温和的运动。

[3]的确，很少有美国人会担心运动过度，因为相对来说，不爱运动是个更普遍、更有害的问题。另外，不是所有研究都发现了过度运动会增加风险，但运动过量的确会带来不良影响。

[4] Here’s a look at some of the latest research, a guide to help you search for the sweet spot in your personal fitness.

What do the data show?

[5] In a British study of more than a million healthy middle-aged women in Circulation, those who were physically active at least once a week were less likely to have heart attacks, strokes or venous thromboembolic events (blood clots in the legs or lungs) over a nineyear period than inactive women.Moreover, any type of physical activity,includ ing gardening and housework,had pretty much the same effects as strenuous activity. But what made headlines was that the women who exercised every day didn’t benefit more than the less frequent exercisers. In fact, they were at greater risk. The women who exercised at least two times a week, and no more than six times, had the lowest cardiovascular risk, compared to infrequent or daily exercisers.

[6] Similarly, a large Danish study in the Journal of the American College of Cardiology, which compared the mortality rates of 1,098 healthy joggers and 3,950 sedentary people, found that those who did light to moderate running (in terms of pace, duration and frequency)were less likely to die over a 12-year period than non-exercisers. But strenuous joggers—fast pace, more than 2 1/2 hours a week, or more than three times a week—had a mortality rate similar to sedentary people. The researchers concluded: “…higher doses of running are not only unnecessary but may also erode some of the remarkable longevity benefits conferred by lower doses of run ning.”

[4]来看看下面这几项最新研究，能帮助你选择最有利于自己健康的运动量。

这些数据说明了什么？

[5]《循环》杂志中有一项为期九年的英国研究，该研究调查了超过100万名身体健康的中年女性，发现每周至少运动一次的女性患心脏病、中风或者静脉血栓栓塞类疾病（腿部或肺部血栓）的概率比不爱运动的人低。该研究还发现，任何形式的体力活动——包括园艺活和家务活都能和剧烈运动达到一样的锻炼效果。然而值得注意的是，相比较少运动的女性，那些每天都运动的女性在健康方面并不占有优势。实际上，每天都运动对女性反而危害更大。与不常运动或者每天都运动的女性相比，那些每周至少运动两次、最多不超过六次的女性患心血管疾病的风险最低。

[6]发表在《美国心脏病学会杂志》上的一项丹麦研究得出相似的结论。该研究比较了1098名健康的慢跑锻炼者和3950名久坐不动的人12年中的死亡率，发现那些跑步适度（根据速度、时间和频率来衡量）的人比不爱运动的人死亡率更低。但是那些跑步剧烈（速度快，每周跑步两个半小时以上或超过三次）的人的死亡率和久坐不动的人相差无几。研究人员得出结论：“……跑步过多不仅没有必要，还可能会逐渐破坏适度跑步给延长寿命带来的显著益处。”

[7] Other studies have found that sedentary people are at higher risk than daily exercisers, but moderate exercisers fared better than both. For instance,a German study in the journal Heart looked at 1,038 people who had stable coronary heart disease and found that both those who were sedentary and those who exercised every day (or did more than about 15 hours of strenuous activity a week) were more likely to die over a 10-year period than those who exercised several times a week—but the risk was greatest for the couch potatoes.

Deciphering the finer points

[8] All of these studies were observational—not randomized, controlled studies—so they can dem onstrate only correlation, not causation. Also in all these studies, there were differences in the way activity levels were categorized, and a relatively small percentage of people exercised at the highest levels. So the studies leave many questions unanswered.

[9] Notably, is there something about people who overdo strenuous endurance exercise that harms their health?Perhaps they are overly competitive or compulsive and tend to overdo other things as well. In contrast, do people who exercise moderately also do other things in moderation, which is generally a healthy way to live? Researchers try to control for such factors, but the likelihood that some such factors are not identi fied or adjusted for remains a concern.

[7]其他研究发现，比起每天都运动的人，久坐不动的人面临更高的风险，但是适度运动的人比前两者的情况都要好。例如，《心脏》杂志中一项德国研究调查了1038位有稳定性冠心病的患者，发现相比一周运动几次的人，久坐不动的人和每天都运动（或者一周中剧烈运动超过15个小时）的人在十年内死亡率更高。不过，久坐不动的人死亡率最高。

细节剖析

[8]以上研究都属于观察性研究，不具有随机性和对照性。因此，它们仅能证明运动量与患病风险之间有相关性，而不能证明二者有因果关系。同时，这些研究界定活动量的方式也有差异，相对来说只有小部分人的运动量达到了最高级别。因此，这些研究也留下了很多未解答的问题。

[9]需要注意的是，是否有其他因素危害这些剧烈耐力运动过量的人的健康？这些人或许在做其他事情的时候也会争强好胜、不加节制吧。做事情有节制通常有益于健康，那么相比之下，那些运动适量的人在做其他事情的时候也会适量而行吗？研究人员会设法控制这些因素对研究的影响，但是可能仍存在类似因素未被发现或未经调整的问题。

[10] How might excessive endurance exercise harm the body, especially when done every day? Besides increasing the risk of injuries, it may depress the immune system and increase inflammatory processes. Taking off a day or two a week gives the body time to recover from the stress of exercise.

[11] Also, some studies of endurance ath letes, usually marathoners, have found coronary changes that may increase the risk of arrhythmias, sudden death and other problems.

[12] Keep in mind, however, that running and other aerobic exercise—no matter how strenuously they’re done—help improve many cardiovascular risk factors, such as blood pressure, cholesterol, and body weight. Thus it’s possible that “high doses” of exercise can benefit some aspects of cardiovascular health while negatively impacting others.

[13] What’s the bottom line? “Too much exercise” varies from person to person. Some of us can exercise strenuously for decades and not suffer any major physical or cardiovascular problems, while others are more susceptible to them, partly for genetic reasons, but also possibly because of differences in training.

[10]过量的耐力运动会如何伤害身体——尤其是在每天都进行的情况下？除了增加受伤风险之外，它还可能使免疫系统功能下降，延长炎症恢复时间。每周休息一至两天可以让身体从运动的压力中恢复过来。

[11]同时，一些对耐力运动员——主要是马拉松运动员的研究发现，冠状动脉的变化可能会使心律不齐、猝死和其他问题的风险增加。

[12]但是请记住，无论跑步和其他有氧运动多么剧烈，它们都可以帮助改善许多影响心血管健康的问题，比如血压、胆固醇和体重。因此可能的情况是，剧烈运动对心血管健康的某些方面是有益的，但对其他方面却是有害的。

[13]到底怎样才算是运动过量呢？运动是否过量因人而异。有些人坚持剧烈运动几十年，从未出现过严重受伤情况或患过心血管疾病，而另一些人更容易出现这些问题，这里面有遗传的原因，但也可能和不同的锻炼方式有关。

[14] There’s no way to say exactly what is the upper limit of exercise for everyone. Generally, any exercise is better than none, and more exercise is usually better within reason. But you certainly don’t have to keep intensifying your exercise regimen to stay healthy.For most people, moderate exercise is the sweet spot. ■

[14]我们无法明确每个人运动的上限是多少。通常来说，任何运动都比不运动好得多，只要不过分，运动越多越好。但你无须通过不断给运动加码来保持健康。对大多数人而言，适度锻炼最有利于健康。 □