Depending on whom you ask, the answer to this question is either one of the great myths of exercise or one of the great unappreciated truths: Does the body burn more calories after a workout?
運動過後身體會繼續消耗更多卡路里嗎？答案可能是否定的，斥之為有關運動的一大迷思；也可能是肯定的，說它是未受應有重視的一大事實，端視你問誰而定。

Over the years, study after study has been carried out, with mixed results about the so-called afterburn effect. Some investigators found no post-exercise effect. Others reported effects so small they were almost unnoticeable – one found male triathletes burned just 12 to 30 extra calories after a workout. Others found as many as 700 additional calories were burned after a long and exhausting exercise session.
關於所謂「後燃燒效應」（指運動過後卡路里仍會繼續消耗的效應）的研究，多年來一個接著一個，結論卻正反都有。有些研究人員發現後燃燒效應並不存在。另一些研究者則指出，這種效應小到幾乎難以察覺。一項研究發現，男性的鐵人三項運動員在運動過後，僅能額外再燃燒12到30卡路里。其他研究卻發現，在長時間做極為耗費體力的運動後，接下來的階段可再消耗700卡。

The latest sally comes in a recent paper in the journal Medicine & Science in Sports & Exercise. Its lead author, Amy A. Knab of Appalachian State University in North Carolina, says it trumps studies that preceded it because of its careful design.
最近發表在「運動醫學與科學」期刊上的一篇報告，提出了最新的說法。報告的主筆、北卡羅來納州阿帕拉契州立大學的艾美．克納布說，這項研究設計嚴謹，勝過先前的研究。

Dr. Knab and her colleagues recruited 10 men, ages 22 to 33, who agreed to spend two periods of 24 hours each in a metabolic chamber. The men were not all athletes, but they did have to be able to ride a bike vigorously.
克納布團隊找來10名22歲到33歲的男性，他們同意在一個小代謝室裡待兩段時間，每次24小時。這些人並非全是運動員，但必須有能猛踩腳踏車的體能。

On the first visit to the chamber, the subjects had to stay perfectly still, sitting in a chair and moving only to eat meals, which were sent in through an air lock. In the afternoon, they were permitted a two-minute stretch every hour. Bedtime was 10:30 p.m. At 6:30 the next morning, the subjects were awakened and allowed to leave. They burned, on average, 2,400 calories on this totally sedentary day.
在第一次進入代謝室時，這些研究對象必須完全靜止不動，坐在椅子上，唯一的動作是用餐，餐食從氣閘送進去。下午，他們獲准每小時伸展兩分鐘。晚上10點半就寢。第二天早上6點半，這些人被叫醒，獲准離開。在這完全靜坐不動的一天，他們平均消耗2400卡熱量。

The second visit to the chamber came two days later. Everything was the same, with one exception. At 11 a.m., the subjects rode a stationary bicycle at a high intensity for 45 minutes.
兩天後第二次進入代謝室。一切照舊，只有一點不同。上午11點開始，研究對象在固定式腳踏車上猛踩45分鐘。

The exercise itself burned about 420 calories, Dr. Knab and her colleagues reported. But what was most interesting was the calories burned afterward. Over the next 14 hours, the men burned an extra 190 calories, increasing the total calories burned by 37 percent.
克納布團隊說，運動本身大約燒掉420卡。但最有趣的是運動後燃燒的卡路里。在接下來的14小時，這些男人又燒掉190卡，使燃燒的總卡數增加37%。

“We were surprised,” Dr. Knab said. She thought there might be extra calories burned, but she did not expect so many, nor did she expect the effect to last so long.
克納布說：「這出乎我們的意料。」她原以為也許會額外燃燒一些卡路里，但沒有預期會這麼多，也沒想到效應會持續這麼久。

She suspects one reason she saw such a pronounced effect was that the exercise was so intense. The subjects had had to cycle at 70 percent of their so-called VO₂ max, the maximum amount of oxygen a person’s body can take in during exercise – an effort that made them breathe too heavily to carry on a conversation. And they had to keep it up for 45 minutes.
她推測她能看到這麼顯著的效應，運動非常劇烈是原因之一。這些研究對象必須以所謂的最大攝氧量的70%來踩腳踏車，最大攝氧量是人體在運動時所能吸入的最大氧氣量 ─ 這麼賣力踩讓他們氣喘吁吁，沒法聊天。而且他們必須連踩45分鐘。

A different study, also using a metabolic chamber, tested the effects of moderate exercise and found no afterburn. Those subjects exercised at 50 percent of their VO2 max, a level that still allows conversation.
另一項研究也在代謝室裡進行，測試溫和運動的作用，結果發現沒有運動後的卡路里消耗效應。這些研究對象運動時達到最大攝氧量的50%，這個程度還能聊天。

Claude Bouchard, a scientist at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, along with other researchers, investigated the exercise effect using a mouthpiece and nose clip or a ventilated hood to determine oxygen used and carbon dioxide exhaled.
布夏是路易斯安納州巴頓魯治市潘寧頓生物醫學研究中心的科學家，他和研究夥伴用口鼻呼吸器或頭罩式呼吸器來測量氧的吸入量和二氧化碳吐出量，以研究運動的效果。

They find, he says, that when studies are done properly, extra calories are burned in the hours after exercise only if subjects exercise at least as hard and long as Dr. Knab’s subjects.
他說，他們發現，當研究做得正確無誤時，研究對象至少要和克納布的研究對象同樣賣力運動，運動時間也一樣長，才會在運動後的幾小時繼續燃燒卡路里。

And if they exercise even harder, they burn even more calories afterward.
而且，如果他們更賣力運動，運動後燃燒的卡路里也會更多。

A recent book that Dr. Bouchard and a colleague edited notes two studies. The researchers found that if subjects ran at 70 percent of their VO₂ max or cycled at 75 percent of it, they could burn 300 to 700 extra calories after the exercise was over, though 700 calories was unusual.
布夏和一名研究夥伴最近編的一本書中，特別提到兩個研究。研究人員發現，如果研究對象以他們最大攝氧量的70%跑步，或是以最大攝氧量的75%踩腳踏車，在運動後可以額外燃燒300到700卡，不過700卡很不尋常。

It is not clear why extra calories should be burned after a bout of intense exercise, Dr. Bouchard says. Part of the effect may be due to post-exercise energy metabolism: Several hormones remain elevated, and the body uses more fat and less carbohydrate. And extra calories may be burned when the body replenishes glycogen, the sugar stored in muscles.
布夏說，目前不清楚何以劇烈運動後會燃燒額外的卡路里。也許可部分歸因於運動後的能量代謝：有幾種荷爾蒙濃度維持在較高水平，身體消耗較多脂肪和較少碳水化合物。身體補充肝糖，也就是儲存在肌肉裡的糖分時，可能消耗了更多卡路里。

But for the most part, the effect remains a mystery.
然而大體來說，這種效應仍是個謎。

原文參照：
http://www.nytimes.com/2011/04/19/health/nutrition/19best.html

2011-07-19/聯合報/G5版/UNITEDDAILYNEWS 田思怡譯  原文參見紐時週報十版上