October 24, 2025, 12:57 pm | Read time: 5 minutes
Some love running through nature, while others prefer the treadmill for their workouts. But do these different preferences have different effects—such as on performance, calorie consumption, or injury susceptibility? FITBOOK editorial director Melanie Hoffmann provides an overview of the pros and cons of both types of running training.
What Burns More Calories?
Many who focus on endurance sports, and especially running, aim to lose weight. So, the question arises: Does it make a difference in calorie consumption whether you run outside or on a treadmill? According to a U.S. study with young participants, energy consumption at a self-selected moderate pace is similar for both training preferences.1 However, the study did not examine how factors like terrain, inclines, or obstacles during outdoor workouts affect calorie consumption.
Those who generally prefer sweating it out in the gym rather than outdoor sports should indeed opt for the treadmill for high calorie consumption. It is more effective in this regard than training equipment such as rowing machines, bicycles, or steppers.2
Running Outside or on the Treadmill: Which Is Gentler on the Joints?
Some runners prefer the treadmill because it is said to be gentler on the joints and less likely to cause injury. Is that true?
Running generally puts pressure on the joints, but can a treadmill really cushion and reduce the load? The previously mentioned study published in “Medicine and Science in Sports and Exercise” found an answer. Surprisingly, the treadmill does not seem to offer a significant advantage over outdoor running in this regard. The study concluded that muscle activity and joint pressure are comparable.
Are Treadmills Safer?
Regarding safety or lower injury susceptibility, treadmill training might have the edge. At least, that’s what a meta-analysis in the “Journal of Sports Health,” which considered ten studies, suggests.3 Treadmill training results in shorter jogging strides than outdoor workouts. The study concluded that the reduced stride length decreases the risk of injury while running.
A benefit of treadmills, but that doesn’t automatically make the equipment safe. In March 2021, the U.S. Consumer Product Safety Commission announced on Twitter: “In 2019, U.S. emergency rooms treated about 22,500 treadmill-related injuries. All age groups were affected (about 2,000 cases involved children under eight years old).”
Additionally, Another Evaluation
An evaluation of American emergency data showed how often people get injured while training on treadmills. Cases from U.S. clinics between 2000 and 2022 were examined. The result: An estimated 451,000 people were treated for treadmill-related injuries during this period. About one-third of these (around 153,000 cases) involved legs, knees, feet, or ankles. The most common injuries were strains or sprains (about 37 percent), bruises (around 18 percent), and fractures (nearly 10 percent). Most of the injured were women (approximately 62 percent), particularly between the ages of 30 and 49. Children were mostly injured at home, while adults were more often affected in gyms. Overall, the number of accidents increased until about 2012, then decreased until 2020 (likely due to the pandemic) and slightly increased again afterward.4
What Benefits Mental Health?
Treadmills can lead to accidents and injuries, not only from falls or unsupervised use by children, but they must also take a back seat to outdoor running when it comes to positive effects on mental health. Perhaps unsurprisingly, but also scientifically proven: Exercise—and thus running—in nature is a true boost for mental health.
British researchers found this in a meta-analysis of studies comparing physical activity in natural environments versus indoors.5 The finding: Those who work out outdoors feel more invigorated, strengthened, and energized, while also 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 couldn’t explain exactly why, but it is suspected that the environment stimulates, while indoor training—despite entertainment options like TV or music—is more monotonous.
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 specifically want to build muscle should ideally combine endurance sports with strength training. Running strengthens muscles and particularly defines those in our legs. For this goal, according to a study from this year, you should lace up your shoes and head outside rather than to the treadmill. A six-week study with a group of recreationally active men found that the skeletal muscle mass of the legs was more positively influenced by outdoor running than treadmill training. Physical fitness also benefited more from movement in a natural environment in the fresh air. At the same time, the study found that regular treadmill running also improved fitness and reduced body fat percentage.6
Conclusion
Overall, outdoor running has the edge because it is more varied and challenging. It promotes both physical fitness and mental health. However, the treadmill can also score points compared to other training equipment. Ultimately, the key is to exercise regularly. Before letting weather or other environmental conditions completely deter you from working out, it’s better to exercise indoors than not at all.