Treadmill Vs Outdoor Running: Which Is Better For Top Performance?

Ah, the trusty treadmill, incredibly convenient and cruel in equal measure. I worked with a client a few years ago who would religiously run 26 miles on a treadmill each Saturday morning down at her local gym.

As a runner who spends the vast majority of their time running on trails, I could never understand the appeal, but believe me, she was fit as a fiddle and as tough as nails.

With a treadmill, rain or shine, you’re in the comfort of a climate-controlled room. No more dodging puddles, battling high winds, or running home with your phone light on because you got lost on a network of trails.

Whether you prefer the controlled environment of a treadmill or the freedom of outdoor running, both options offer unique benefits and drawbacks.

But is there any difference between the performance and physiological aspects between treadmill vs outdoor running?

In this article, we will cover the following:

  • Treadmill Vs Outdoor Running: Physiological Differences
  • Treadmill Vs Outdoor Running: Performance Differences
  • 5 Reasons You Should Run Outdoors
  • 5 Reasons You Should Run On A Treadmill

Let’s get into it!

A person running on a treadmill.

Treadmill Vs Outdoor Running: Physiological Differences

There are a number of physiological differences to note when comparing treadmill running to outdoor running.

Most notably:

Shock Absorption

One study observed that treadmill running tends to provide more shock absorption and vertical deformation compared to outdoor surfaces like concrete, artificial turf, or tracks. However, it didn’t look at other surfaces, such as grass and trails.

This means that when you run on a treadmill, the surface is better at absorbing the impact of your steps, potentially reducing stress on your joints. It should be noted that different treadmills will provide different levels of shock absorption.

In fact, a study published in 2017 demonstrated that the physical exertion needed for treadmill running can fluctuate by five to seven percent, contingent on the rigidity of the treadmill surface.

A person running on a treadmill.

Muscle Engagement

When we compare the activity of key lower limb muscles, we find some notable variations.

Running on grass and concrete surfaces generally requires greater muscle engagement in muscles like the tibialis anterior, peroneus longus, soleus, gastrocnemius medialis, vastus medialis, to name a few…

This suggests that outdoor running on these surfaces may demand more from these specific muscles compared to treadmill running. When we are running on varying terrain, our muscles have to activate to correct for the twists and turns of trails and paths.

You can look at this one of two ways: either running outside offers more bang for your buck by more significant muscle engagement, or the extra muscle engagement increases the risk of injury.

Despite a broad range of opinions in the running world, the main mechanics of the running gait remain largely similar across key lower limb muscles for both treadmill and outdoor running.

Running on a treadmill.

So, does more absorption mean less injury?

As for the injury prevention aspect of the shock-absorbing properties of a treadmill, there is little evidence to show that treadmills offer a significant reduction in injury rates.

There is one key factor that underpins the majority of running injuries, and that is the progressive overload principle. I’ve written about it extensively, and it’s a great principle to get your head around.

Our bodies need time to adjust to training loads; if we aren’t supplying our bodies with a well-thought-out and progressive training plan, lots of sleep, and sufficient nutrition, we risk not fostering a nourishing environment for them to adapt to the stimulus of training.

You’re better off gradually increasing your running volume outdoors than you are suddenly and significantly increasing your volume on a treadmill, even if there is sometimes more absorption.

People running on treadmills.

Treadmill Vs Outdoor Running: Performance Differences

It has long been thought that because of the lack of air resistance, running on the treadmill was “easier” than running outside. For years, runners have been told to adjust the treadmill to a 1% gradient in order to nullify the difference to outdoor running.

However, in recent years, studies have continually shown a statistically insignificant difference in performance when comparing treadmill running to outdoor running. For speeds slower than six minutes per mile, there’s no need to set the treadmill incline.

Let’s take a look at a couple of specific metrics comparing running performance:

Oxygen Consumption

When running on the flat, oxygen consumption appears to be similar for both treadmill and outdoor running. This similarity persists for inclined running (5.7% grade).

The oxygen demand for running is comparable between treadmill and outdoor conditions, both for level and inclined running.

The prevailing view that overground hill running is more costly than inclined treadmill running was not supported by the empirical findings of this study.

A person running on a treadmill.

Heart Rate And Perceived Rate Of Exertion

A 2019 Meta-analysis comparing physiological, perceptual, and performance measures between treadmill and overground running found that heart rate and perceived exertion followed a U-shaped curve, dependent upon the speed at which the runner is running.

A U-shaped curve means that running at slow paces on a treadmill feels easier with lower heart rates, while fast speeds elicit higher heart rates and a harder perceived effort.


Overall running performance, measured by both distance and time, was consistently worse on the treadmill, attributed to the aforementioned increased rate of perceived effort and heart rate at high speeds. This performance drop is seen in the “U-shaped curve.”

Although performance during tough workouts or interval sessions may be worse on the treadmill, a firmer treadmill platform can help mitigate this effect. On top of that, the meta-analysis found that easy runs might feel easier on a treadmill!

A person running outside in the sun.

5 Reasons You Should Run Outdoors

Outdoor running, whether on trails, roads, or tracks, offers unique advantages:

#1: Immersion In Nature

When you run outdoors, you are immersed in the beauty of the natural world.

The changing of seasons brings an ever-shifting landscape, from the vibrant colors of spring flowers to the golden hues of autumn leaves. Even the worst weather can feel incredibly exhilarating.

Being immersed in nature allows us to become attuned to the stillness of our surroundings, something that can be quite rare in our fast-paced society.

#2: Mental Wellbeing

Running outdoors provides us with a plethora of mental health benefits. It has been shown to reduce stress, improve mood, and enhance mental well-being.

Few things make me feel more present than watching a sunrise atop a hill I’ve just run up. Although, in fairness, there have been a few times I’ve had to jump a fence to avoid a charging herd of cattle, which is rather stress-inducing.

Runners will likely experience a positive effect on their mental well-being, irrespective of whether they’re running outdoors or on a treadmill!

Two people running outside.

#3: Vitamin D Exposure

Over 40% of Americans are vitamin D deficient. Running outdoors exposes you to natural sunlight, increasing vitamin D production, which is crucial for overall health.

#4: Community

Running outdoors can create opportunities for social interaction. For example, you might opt to go for a jog with a friend or join a local running group.

A study conducted in 2022 discovered that the more running partners individuals had, the more frequently they engaged in running sessions.

Moreover, when runners could identify a key running buddy, they reported receiving increased social support for their running endeavors.

#5: Race Simulation

Have you ever signed up for an indoor treadmill marathon? No? Me neither. Although treadmills effectively recreate the performance and training aspects of running, it is lacking in the real-life experience of running on trails or concrete.

Running outdoors offers different routes, varying surfaces, and obstacles that you might experience during a race.

People running in a group.

5 Reasons you should run on a treadmill

Treadmills offer unique advantages, these are:

#1: Precise Workouts

One of the key advantages lies in the ability to effectively manage the workout. You can easily adjust the speed, incline, and duration of your run at the push of a button, enabling precise and consistent training.

This degree of control can prove especially valuable for novices who are in the process of developing their endurance and speed. It’s easy to speed up or slow down when you’re running outside.

Treadmills are also equipped with built-in monitors that provide real-time metrics for monitoring data.

#2: No Weather Woes

You’re all set for a fantastic outdoor run, but the heavens open, and you’re slipping and sliding and wishing you’d gone to the gym and jumped on the treadmill.

You can run on a treadmill regardless of weather conditions, ensuring consistent training all year round.

Additionally, in the winter months, when it seems to be dark all day, you can rest assured that you have a well-lit, environment-controlled area to run in.

Running on treadmills.

#3: Joint-Friendly

As mentioned earlier, treadmills typically provide a cushioned surface, reducing the impact on joints and possibly reducing injury risk.

#4: Consistent Terrain

If, like me, you live in a hilly or mountainous area, flat runs are a pipe dream. Treadmills offer a great way of getting on those flat and consistent treadmill surfaces, ideal for specific training like interval runs or speed workouts.

#5: Rehabilitation

Treadmills have a particularly useful role in rehabilitation. Due to their immovable nature, they allow a physio or coach to work directly with a client in a controlled and highly adaptable manner.

A person running outside.

Final Thoughts

There is no clear-cut better option when it comes to treadmill and outdoor running.

Each has its unique advantages, and the decision hinges on personal preferences and objectives. Some runners favor the controlled setting and ease of treadmills, while others value the mental and sensory rewards of outdoor running.

Many individuals blend both types into their fitness routines to benefit from both experiences.

Ultimately, the choice that suits you best is the one aligned with your fitness goals and provides the most fulfillment and pleasure.

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Ben is a qualified Personal Trainer and Sports Massage Therapist with a particular interest in running performance and injury. He has spent the last 9 years working with runners at his clinic in Brighton. Ben is a keen runner and avid cyclist. Evenly splitting his time between trail running, road biking, and MTB.

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