September 12, 2026, 4:11 pm | Read time: 5 minutes
Some prefer running through nature, while others complete their training on a treadmill. But does it make a difference to the body whether you run outside or on a treadmill, in terms of performance, calorie consumption, or injury risk? FITBOOK provides an overview of the pros and cons of both forms of running.
What Burns More Calories?
Many people turn to endurance sports, especially running, to lose weight. This raises the question of whether there is a difference in calorie consumption between running outside or on a treadmill. A U.S. study with young adults found that energy expenditure at a self-selected, moderate running pace was similar under both conditions.1 However, possible influencing factors of outdoor running, such as different terrains, inclines, or obstacles, were not considered. These can also affect physical exertion and thus calorie consumption.
Those who generally prefer training in the gym rather than outdoors and want to burn as many calories as possible may find the treadmill a good option. Depending on the intensity of the workout, running can allow for higher energy expenditure than training on equipment like rowing machines, stationary bikes, or steppers.2
What Is Gentler on the Joints?
Some runners prefer the treadmill because it is considered gentler on the joints and is thought to have a lower risk of injury. But is that really true?
Running generally exerts forces on muscles and joints. While many treadmills offer some cushioning, this does not necessarily mean a significant advantage over outdoor running. This is also suggested by the aforementioned study published in “Medicine & Science in Sports & Exercise”: Muscle activity and joint stress were comparable when running on a treadmill and outdoors.
Are Treadmills Safer?
In terms of injury risk, the treadmill may still offer certain advantages. This is suggested by a meta-analysis that considered the results of ten studies.3 According to this, running behavior on the treadmill differs in part from running outdoors. Among other things, stride length was shorter on the treadmill.
A shorter stride length can reduce certain stresses while running and is therefore associated with a potentially lower risk of injury. However, it cannot be definitively concluded from this that treadmill training actually protects against running injuries overall.
Newer data, however, suggest greater differences than long assumed. In a 2025 study published in the “Journal of Biomechanics,” 71 physically active adults ran five kilometers outside and five kilometers on a treadmill. Sensors on their shoes recorded each step. The running mechanics differed significantly, especially in the forces exerted and the inward rolling of the foot. Whether this affects the risk of injury in the long term cannot be determined from such snapshots.4
That injuries can also occur during treadmill training is shown by an analysis of data from U.S. emergency rooms. Treadmill accidents between 2000 and 2022 were examined. It is estimated that around 451,000 people required medical treatment for such accidents during this period.
About one-third of the injuries involved legs, knees, feet, or ankles. The most common diagnoses were strains and sprains (about 37 percent), followed by bruises (about 18 percent) and fractures (nearly 10 percent). About 62 percent of those injured were women. People between the ages of 30 and 49 were particularly affected.
There were also differences in the location of the accidents. Children were more likely to be injured at home, while adults were more often injured in the gym. Overall, the number of treadmill accidents initially increased until about 2012, then decreased, and rose slightly again after 2020.5
What Benefits Mental Health?
In one aspect, running outdoors has a clear advantage over the treadmill. Exercising in the fresh air, especially in nature, can have a positive effect on the psyche. This is also indicated by scientific studies. Exercise in a natural environment can promote well-being and reduce stress.
British researchers found this in a meta-analysis of studies comparing physical activity in natural environments versus indoors.6 The finding: Those who work out outdoors feel more invigorated, empowered, and energized, while feeling less tense, confused, angry, or depressed. Outdoor athletes were also more likely to say they wanted to repeat their workout soon and stay committed. The analysis could not explain exactly why this is. However, it is suspected that the environment is stimulating, while training indoors—despite entertainment options like TV or music—is more monotonous.
What seems crucial here is less the act of being outdoors itself than the environment. A British review from 2022 compared studies in which people moved once in nature and once in the city—both outdoors. Medium to large effects on anxiety, fatigue, mood, and vitality were found in favor of nature. So jogging through the city center may be less beneficial psychologically than running through the park.7
Rowing, Cycling or Running–Which Builds More Muscle and Burns More Calories?
Incline Walking vs. Running: Study Shows Which Burns More Fat
What Trains the Muscles Better?
Those who want to build muscle should ideally combine endurance training with strength training. Nevertheless, running also engages the muscles, especially in the legs. A study suggests that outdoor running may have advantages over treadmill training in this regard. In the six-week study with physically active men, the skeletal muscle mass of the legs increased more with outdoor running than with treadmill training. The group that trained outdoors also performed better in terms of physical fitness. However, regular treadmill training also showed benefits: Participants improved their fitness and reduced their body fat percentage.8
Conclusion
Overall, running outdoors offers several advantages. Varying surfaces and external conditions can make training more diverse. At the same time, exercising in nature can also have positive effects on mental well-being. But the treadmill also has its strengths, allowing for well-controlled training—regardless of weather and time of day.
Whether a treadmill or outdoor running is the better choice also depends on personal preferences and training goals. The key is to stay active regularly. If rain, cold, or other external conditions deter you from running outside, a session on the treadmill is certainly better than skipping the workout altogether.