After rigorous exercise, muscle pain is more acute a day or two later rather than immediately. Why?

剧烈运动之后的第二天或第三天，肌肉会比运动刚结束时更加酸痛。为什么会出现这种情况呢？

Welcome to the equivocal effects of delayed onset¹ muscle soreness, the scientific term for aches that accumulate and intensify² a day or two after a strenuous³ workout. Usually, D.O.M.S. involves not just pain but also “loss of strength and range of motion in the affected⁴ area,” said Scott Sailor, a professor of kinesiology at Fresno State University in Fresno, Calif., and the president of the National Athletic⁵ Trainers’ Association.

其背后原因是让人感觉莫名其妙的延时发作肌肉酸痛（delayed onset muscle soreness，简称DOMS），这一科学用语用来定义高强度锻炼结束一两天后积累和加剧的肌肉酸痛。通常，DOMS不仅仅是痛，“受到影响的身体部位还会感到无力和活动困难，”位于加州弗雷斯诺市的加州州立大学弗雷斯诺分校的运动机能学教授、美国运动伤害防护协会(National Athletic Trainers’ Association)主席斯科特·赛勒(Scott Sailor)说。

D.O.M.S. commonly occurs after exercise that involves lengthening⁶ muscles while they contract, Dr. Sailor said, such as running downhill. But it can develop after any exertion⁷ that is more intense or prolonged than is normal for you.

赛勒博士表示，在肌肉处于收缩状态时进行拉伸，比如下坡奔跑，通常会引起DOMS。但是，任何强度或时长超过自身正常接受范围的运动，都有可能导致DOMS。

Such strenuous workouts can cause multiple slight tears to the muscle tissue, after which a variety of cells and substances migrate to these muscles to help them start healing.

剧烈运动会导致肌肉组织出现很多轻微撕裂，之后各种细胞和物质会移动到这些肌肉组织中，帮助它们开始愈合。

Interestingly, these substances are not necessarily the same as those that arrive after a more severe muscle injury. Molecules⁸ that promote inflammation and swelling⁹, for instance, tend to predominate in tissues affected by a serious injury, but can be absent in tissue affected by D.O.M.S., recent studies show.

有趣的是，这些物质与经过更严重的肌肉拉伤后出现的物质不一定相同。比如，最近的一些研究显示，会促发炎症和肿胀的分子，比较多出现在严重拉伤后的肌肉组织中，而在有DOMS症状的轻微受损组织中却不存在。

Similarly, “there was a time when we attributed the muscle soreness to lactic¹⁰ acid,” Dr. Sailor said. “We have now learned that lactic acid leaves the muscle so quickly” that it cannot be involved in causing D.O.M.S.

同样有意思的是，“我们一度把肌肉酸痛归因于乳酸的存在，”赛勒博士说。“现在我们知道，乳酸很快会从肌肉中消失”，所以它不会引起DOMS。

In essence, researchers remain puzzled about what cellular¹¹ reactions cause D.O.M.S. There is also controversy¹² about how to treat it.

实际上，研究人员还没弄清楚，到底是什么细胞反应引起了DOMS。对于如何治疗它，也存在争议。

“Various treatments have been attempted over the years,” said Dr. Sailor, including massage¹³, icing and anti-inflammatory painkillers¹⁴. “At best, they have decreased the perception of pain,” he said, but only temporarily.

“过去多年，我们尝试过各种治疗方法，”赛勒博士说，包括按摩、冰敷和服用消炎止痛药物。“这些办法至多能减轻一些疼痛感，”他说，而且其作用也是暂时的。

So if you do develop D.O.M.S., accept that, for the next five to seven days, you are going to be sore. Refrain from strenuous exercise during this time, Dr. Sailor said, although gentle walking is fine. And, if it is any consolation¹⁵, your muscles should be stronger after they recover.

所以如果你出现了DOMS症状，只能忍着，接下来的五到七天里，它会一直都会疼下去。赛勒博士表示，这段时间里，不宜进行剧烈运动，可以徐缓地散散步。要说有什么能让你感到安慰，那就是在恢复之后你的肌肉应该会变得更强壮。

In your future workouts, Dr. Sailor said, increasing the duration or intensity¹⁶ gradually should increase strength and fitness to limit the potential of experiencing the effects of D.O.M.S.

赛勒博士表示，在以后的运动中，逐步增加运动时长和强度，应该可以增强肌肉力量和适应性，进而减少出现DOMS的情况。