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.

大多數人都希望能多運動，畢竟我們當中能達到推薦運動量的人還不足一半，大家都清楚這一點。但好東西過了頭會不會適得其反呢？

[2]答案是肯定的。運動于健康大有裨益，但如果運動太劇烈或運動時間過長，則會增加受傷風險，產生負面效果。一般來說這種情況只出現在劇烈運動后，比如馬拉松訓練或者耐力運動。此類有挑戰性的運動固然不錯，甚或值得提倡，但研究認為，要達到最佳鍛煉效果，還是要選擇更溫和的運動。

[3]的確，很少有美國人會擔心運動過度，因為相對來說，不愛運動是個更普遍、更有害的問題。另外，不是所有研究都發現了過度運動會增加風險，但運動過量的確會帶來不良影響。

[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]來看看下面這幾項最新研究，能幫助你選擇最有利于自己健康的運動量。

這些數據說明了什么？

[5]《循環》雜志中有一項為期九年的英國研究，該研究調查了超過100萬名身體健康的中年女性，發現每周至少運動一次的女性患心臟病、中風或者靜脈血栓栓塞類疾?。ㄍ炔炕蚍尾垦ǎ┑母怕时炔粣圻\動的人低。該研究還發現，任何形式的體力活動——包括園藝活和家務活都能和劇烈運動達到一樣的鍛煉效果。然而值得注意的是，相比較少運動的女性，那些每天都運動的女性在健康方面并不占有優勢。實際上，每天都運動對女性反而危害更大。與不常運動或者每天都運動的女性相比，那些每周至少運動兩次、最多不超過六次的女性患心血管疾病的風險最低。

[6]發表在《美國心臟病學會雜志》上的一項丹麥研究得出相似的結論。該研究比較了1098名健康的慢跑鍛煉者和3950名久坐不動的人12年中的死亡率，發現那些跑步適度（根據速度、時間和頻率來衡量）的人比不愛運動的人死亡率更低。但是那些跑步劇烈（速度快，每周跑步兩個半小時以上或超過三次）的人的死亡率和久坐不動的人相差無幾。研究人員得出結論：“……跑步過多不僅沒有必要，還可能會逐漸破壞適度跑步給延長壽命帶來的顯著益處?！?/p>

[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]其他研究發現，比起每天都運動的人，久坐不動的人面臨更高的風險，但是適度運動的人比前兩者的情況都要好。例如，《心臟》雜志中一項德國研究調查了1038位有穩定性冠心病的患者，發現相比一周運動幾次的人，久坐不動的人和每天都運動（或者一周中劇烈運動超過15個小時）的人在十年內死亡率更高。不過，久坐不動的人死亡率最高。

細節剖析

[8]以上研究都屬于觀察性研究，不具有隨機性和對照性。因此，它們僅能證明運動量與患病風險之間有相關性，而不能證明二者有因果關系。同時，這些研究界定活動量的方式也有差異，相對來說只有小部分人的運動量達到了最高級別。因此，這些研究也留下了很多未解答的問題。

[9]需要注意的是，是否有其他因素危害這些劇烈耐力運動過量的人的健康？這些人或許在做其他事情的時候也會爭強好勝、不加節制吧。做事情有節制通常有益于健康，那么相比之下，那些運動適量的人在做其他事情的時候也會適量而行嗎？研究人員會設法控制這些因素對研究的影響，但是可能仍存在類似因素未被發現或未經調整的問題。

[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]過量的耐力運動會如何傷害身體——尤其是在每天都進行的情況下？除了增加受傷風險之外，它還可能使免疫系統功能下降，延長炎癥恢復時間。每周休息一至兩天可以讓身體從運動的壓力中恢復過來。

[11]同時，一些對耐力運動員——主要是馬拉松運動員的研究發現，冠狀動脈的變化可能會使心律不齊、猝死和其他問題的風險增加。

[12]但是請記住，無論跑步和其他有氧運動多么劇烈，它們都可以幫助改善許多影響心血管健康的問題，比如血壓、膽固醇和體重。因此可能的情況是，劇烈運動對心血管健康的某些方面是有益的，但對其他方面卻是有害的。

[13]到底怎樣才算是運動過量呢？運動是否過量因人而異。有些人堅持劇烈運動幾十年，從未出現過嚴重受傷情況或患過心血管疾病，而另一些人更容易出現這些問題，這里面有遺傳的原因，但也可能和不同的鍛煉方式有關。

[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]我們無法明確每個人運動的上限是多少。通常來說，任何運動都比不運動好得多，只要不過分，運動越多越好。但你無須通過不斷給運動加碼來保持健康。對大多數人而言，適度鍛煉最有利于健康。 □