For those in the doldrums, few things are more tiresome than being told to exercise. But unwelcome advice is not necessarily wrong. Study after study has found that exercise boosts mood and reduces anxiety. Two large analyses published earlier this year go further, suggesting it works about as well as therapy or antidepressants.

对于那些情绪低落的人来说，没有什么比被劝去锻炼更令人厌烦的了。 但不受欢迎的建议未必就是错误的。 一项又一项研究发现，锻炼能改善情绪、减轻焦虑。 今年早些时候发表的两项大型分析研究更进一步，表明锻炼的效果与心理治疗或服用抗抑郁药物的效果大致相当。

The first, published in January by researchers based across Britain and Ireland, took the form of a Cochrane review—a well-regarded meta-analysis of health-care research. It pooled the results of 69 randomised-controlled trials (RCTs) conducted to measure the effects of exercise on depression. The second paper, published in February in the British Journal of Sports Medicine, was a so-called meta-meta-analysis. It drew on more than 1,000 trials involving nearly 80,000 participants. Both concluded that exercise reduces symptoms of depression and anxiety by roughly as much as conventional treatments.

第一项研究于1月份发表，由英国和爱尔兰各地的研究人员完成，采用了考科蓝综述的形式——这是一种备受认可的医疗保健研究荟萃分析。 该研究汇总了69项随机对照试验（RCTs）的结果，这些试验旨在测量锻炼对抑郁症的影响。 第二篇论文于2月份发表在《英国运动医学杂志》上，是一项所谓的“元元分析”。 它借鉴了1000多项试验的数据，涉及近8万名参与者。 两项研究都得出结论：锻炼对减轻抑郁和焦虑症状的效果大致与传统疗法相当。

There are important caveats. Meta-analyses are only as good as the studies they include, and exercise trials are prone to being skewed. For one thing, participants cannot be blinded—they know if they are doing kettlebell swings or not—which makes their self-reported mood vulnerable to any favourable expectations they might have. For this and other reasons, the Cochrane review judged all the studies it included to be at "high risk" of bias.

不过，这其中存在一些重要的注意事项。 元分析的质量取决于其所纳入的研究，而锻炼试验往往容易出现偏差。 首先，参与者无法被设盲——他们知道自己是否在做壶铃摆举等动作——这使得他们自我报告的情绪容易受到任何可能存在的积极预期的影响。 由于这些和其他原因，考科蓝综述认为其纳入的所有研究都存在“高”偏倚风险。

What's more, the meta-meta-analysis did not include any studies that tested exercise against other interventions. The findings from the exercise trials were, instead, compared against those from separate trials of antidepressants or therapy. But unlike exercise studies, RCTs of antidepressants are typically well blinded and have strong placebo effects, making it harder for them to achieve similarly impressive results. "I don't think it's a fair comparison," says Jonathan Roiser, a professor of neuroscience at University College London.

此外，这项元元分析并未纳入任何将锻炼与其他干预措施进行对比的研究。 相反，锻炼试验的结果是与单独进行的抗抑郁药物或心理治疗试验的结果进行比较的。 但与锻炼研究不同，抗抑郁药物的随机对照试验通常设盲良好，且存在较强的安慰剂效应，因此这些试验更难取得同样显著的效果。 伦敦大学学院神经科学教授乔纳森·罗伊泽表示：“我认为这样的比较并不公平。”

All the same, most researchers are confident that exercise helps improve mood. Aerobic workouts, such as running, walking or cycling, seem to be particularly beneficial across the board. For depression, group-based or supervised exercise is more effective than sweating alone, and the benefits of exercise accrue over several months. For anxiety, the best results seem to come from lower-intensity activity.

尽管如此，大多数研究人员都相信锻炼有助于改善情绪。 有氧运动，如跑步、步行或骑自行车，似乎对所有人都特别有益。 对于抑郁症，团体或有人监督的锻炼比独自锻炼更有效，而且锻炼的益处会随着几个月的时间逐渐累积。 对于焦虑症，低强度运动的效果似乎最佳。

Why exercise works is less clear. The popular idea that exercise generates a "high" by causing the release of endorphins, a form of opioid, has little scientific support. A study published in 2021 found that blocking runners' opioid receptors reduced neither the euphoria they reported after a session nor the drop in anxiety. Researchers instead think that endocannabinoids—chemicals produced by the body and brain that activate the same receptors as the active molecules in cannabis—might be responsible for these short-term boosts.

至于锻炼为何能起作用，目前尚不清楚。 一种流行的观点认为，锻炼通过促使内啡肽（一种阿片类物质）的释放而产生“快感”，但这一观点缺乏科学依据。 2021年发表的一项研究发现，阻断跑步者的阿片受体既不会降低他们跑步后报告的愉悦感，也不会减轻焦虑感的下降。 研究人员转而认为，内源性大麻素——由人体和大脑产生、能激活与大麻中活性分子相同受体的化学物质——可能是造成这些短期情绪提升的原因。

Other pathways are also being triggered. Exercise seems to reduce inflammation and improve brain plasticity, as well as increasing the transmission of dopamine in the brain. Dopamine is involved in the process of weighing effort against reward and so increasing transmission may help reverse the loss of motivation associated with depression.

其他途径也被激活。 锻炼似乎能减轻炎症、改善大脑可塑性，并增加大脑中多巴胺的传递。 多巴胺参与权衡努力与回报的过程，因此增加其传递可能有助于逆转抑郁症相关的动力缺失。

There are purely psychological benefits, too: exercise can provide people with a sense of achievement, agency and eventually mastery, all of which are known to lift mood. Plenty of reasons, then, to work up a sweat.

锻炼还有纯粹的心理益处：它能给人带来成就感、掌控感，并最终带来精通感，而这些都被证实能改善情绪。 因此，有充分的理由让我们动起来、出一身汗。

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