Summer is at its peak, and those trying to stay fit by running find themselves debating between running outdoors, in the stifling heat of over thirty degrees, and running inside, on a treadmill, which never feels the same. But can the latter type of running be as effective a workout as the first? Perplexity summarizes for us what experts say about it:
Energy
According to Bas van Horn, a competitive runner and researcher at Maastricht University in the Netherlands, running on a treadmill is generally as effective as running outdoors. While energy consumption for walking is "very low," the differences are minor. For example, at speeds up to 16 km/h, running a treadmill causes similar oxygen consumption and heart rate compared to running outdoors. However, the slight difference in energy consumption can add up in someone who does most or all of their workouts on a treadmill.
Slant
Some runners use treadmills with a positive incline (increase) of 1% in an effort to compare the energy costs of running on them to running outdoors – but according to Van Horn, this is not necessary. Keeping the treadmill on a zero incline is fine. Increasing the incline on treadmills can be useful to diversify your workouts.
Running form
Unlike outdoor runs, where the runner pushes his body forward from the ground, when running on a treadmill the belt moves underneath him and he just needs to bounce a little and land back. People who are not used to treadmill running may therefore adopt a slightly higher frequency of steps and land a little more towards the front of their foot compared to the heel of their foot. The rigidity of the treadmill is also important. It can affect how you run and even your leg injury. A very rigid treadmill will cause runners to adopt steps that start with landing the heel, which may take some load off the Achilles tendon, but increase the load on the knee. In contrast, on a more bouncy treadmill, runners tend to adopt steps starting from the front of the foot, which puts more strain on the Achilles tendon but less strain on the knee. Science does not prioritize either of these types of measures.
Feeling of effort
The physiological demands of running on and off a treadmill are similar, but the feeling of strain of running on a treadmill may be higher. In a 2019 paper, Van Horn and his colleagues speculated about why runners prefer to run outdoors, noting that this could be due to a preference for greater control over speed and timing of stops, as well as a lower risk of falls. Another reason may be that the body temperature during a treadmill run indoors increases due to less airflow.
So how to train?
According to Olympian Kim Connelly, running on a treadmill takes the mental load off speed work or repetitive runs up hills, which in the real world you have to descend to climb again, while on a treadmill you can just keep running on a steady incline.
The bottom line is that there are no significant differences between running on a treadmill and running outdoors, so choosing between these two types of running is a matter of personal preference.
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