一项研究表明，跑步者在跑步机上的速度要比户外慢跑快15%，才能与其燃烧同等热量。
Runners need to move 15 per cent faster on a treadmill to burn the same number of calories as jogging outdoors, research reveals.
意大利米兰大学的研究人员分析了平均年龄为21岁的15名健康男子去户外跑步与在跑步机上跑步的差异。
Researchers from Milan University analysed the difference between running outdoors or on a treadmill in 15 physically fit males with an average age of 21.
参与者先快跑30秒，然后休息30秒，这样分别在户外和跑步机上运动15分钟。
The participants sprinted for 30 seconds followed by 30 seconds of recovery for a total of 15 minutes both outdoors and on a treadmill.
研究人员会在两种类型的跑步后，测量参与者的耗氧量和运动强度。研究成果发表在加拿大《应用生理学、营养与代谢》杂志上。
Oxygen use and exercise intensity were measured after both types of running. The findings were published in the journal of Applied Physiology, Nutrition and Metabolism.
结果显示，在跑步机上跑步时，跑步者的耗氧量大大降低，表明这种方式更省劲。
Results revealed that when on a treadmill, runners use significantly lower amounts of oxygen, suggesting less effort is required.
该研究的作者写道：“在高间歇强度跑步机训练期间，跑步速度增加15%，是达到与户外锻炼同样生理反应的最佳解决方案。”
The study authors wrote: 'A 15 per cent increase in running velocity during a high intermittent intensity treadmill training session is the optimal solution to reach the same physiological responses as an outdoor training session.'
尽管这项研究没有推测为何在跑步机上跑步似乎更省力，但以往的研究指出，跑步机上移动的跑带会推动跑步者向前，从而让他们跑得更快。
Although the study did not speculate why treadmill running appears to be less strenuous, previous research suggests the moving belt of a treadmill propels joggers forward, causing them to move faster.
此外，室内锻炼还意味着锻炼者不必应付陡峭的山坡或风的阻力。
Exercising indoors also means gym-goers do not have to contend with steep hills or wind resistance.