In the dark days of winter, opting to run on an indoor treadmill rather than braving the cold may seem tempting. But does it bring the same effects?

One thing that could make the treadmill easier is the lack of air resistance- you don’t have to displace the air in front of you when you run on the spot. To make up for this and to ensure indoor workout isn’t too easy, some people religiously set the treadmill’s incline to 1%. That figure originated from a 1966 study that found runners doing a 7-minute-per-ile pace used similar amounts of energy to run over ground as they did on a treadmill with a 1% incline. However, at slower speeds, there were no differences in the energy costs of running over ground or on a flat treadmill.

Many people think the “dreadmill”feels harder, not easier. Runners on a treadmill asked to replicate a pace they had previously run on a track, for example, jogged more than 2 minutes per mile slower. Irene Davis at Harvard Medical School, who studies the biomechanics of running, has seen the same thing- people find that comfortable paces suddenly seem less so on the treadmill. She blames the treadmill forcing you to maintain one speed, which is tiring and unnatural. When you run outdoors, “you’re constantly speeding up and slowing down and probably adjusting your speed to your fatigue level”, she says.

Another explanation is the lack of visual cues that help you gauge your pac. A review of studies compared exercising indoors and outside found that people who worked out in the fresh air had higher levels of satisfaction and enjoyment, and said they were more likely to do it again than those who exercised indoors. Davis recommends adjusting the speed throughout the workout according to how you feel. “Your body is meant to be loaded in lots of different ways”- whether its easy or not. Teal Burrell. New Scientist Jan 2018