Treadmill Vs Running Outside: Which Is Better And Why?

Treadmill Vs Running Outside: Which Is Better And Why?

The debate between a treadmill vs running outside has been raging for years.

Most people think that there is a single, definitive answer. It turns out that most people would be wrong. Both running environments have their upsides and downsides. The best option comes down to each individual runner’s goals, health, local environment, and skill level. This isn’t based on opinion alone. Multiple universities and health companies have funded studies to determine the answer once and for all.

Every study turns up the same answer: the best option is the one that suits the runner’s needs and abilities. Some may opt to run on a treadmill vs running outside; others may prefer the opposite. In other words, there really is no universal answer. Just individual ones.

Deciding Factors

Local Conditions

Runners have to consider their local weather, terrain, and safety level when choosing whether to run indoors or out. Some areas do not offer hills while others are not flat enough. Harsh weather conditions may drive runners indoors. And some runners may not live in an area with outdoor running spaces or they may not be comfortable running outdoors at certain times such as rush hour or after dark.

Fitness Level

A runner’s needs will change as they move from ‘beginner‘ to ‘experienced’. Their body will adjust to the strain of running and they will slowly find themselves capable of pushing new limits. A person’s needs will also change if they are injured or fall ill. And as these needs change, so does the answer to whether running on a treadmill vs the outdoors is better.

Training Goals

There are almost as many training goals as there are runners to pursue them. Some runners want to win marathons or improve their forms. Similarly, some runners just want to go faster while others want to go farther. And under each of these larger goals are countless smaller goals that motivate runners to lace up their shoes and get on their feet. Whether they hit the pavement or head for the treadmill depends on which goals they’re pursuing.

Health Concerns

Any runner with an injury or health concern will attest that it changes everything. Their pace and their form are affected, as is the location best suited for their runs. Some conditions are helped by getting outdoors, particularly when it is sunny or the run takes place somewhere with fresh air. Other conditions make the treadmill a better-suited option because of the controlled climate, monitored location, and lack of a return run. And certain conditions might require abstinence. It’s important to be mindful.

Running Outside Vs On a Treadmill

The Pros

The most popular image of a runner is that of a lone figure on a sidewalk or trail. This person most often runs shortly after dawn with a laser-like focus on the path ahead of them. Most runners can tell you that’s not always the case, but the image has persisted for a reason. Outdoor running is the most popular form of the sport, whether the popularity in question is that of racing or training. There are several upsides to running outside that treadmills cannot match.

Mimics Race Conditions

Nearly every race is held outdoors. This means that the best way to train for a race – whether it is a half-marathon or an ultra-marathon – is to run outdoors. It is the only way to properly mimic race conditions. Such conditions can include weather, wind resistance, and dodging obstacles like curbs or pedestrians. These conditions simply cannot be mimicked on a treadmill, just as a treadmill cannot mimic the variations in terrain elevation and material.

Uses More Energy

A treadmill’s inability to perfectly mimic outdoor terrain does more than impact its efficacy for marathon training. It also means that treadmill runners burn less energy per footfall than outdoor runners. Running outside means that every step a runner takes has to account for wind resistance and slight changes in terrain. Outdoor runners also have to propel themselves along the ground while a treadmill feeds the belt beneath a runner’s feet. Most studies have shown that a runner’s biomechanics – the way their body moves as they run – are the same outside as on a treadmill. But that does not change the lost energy burn associated with running inside.

Better for Bone Density

Outdoor runners get another benefit, footfall for footfall, over indoor runners. Running on hard surfaces such as packed dirt or pavement forces the body to increase bone density. This is a long-term process but studies have shown its impact time and again. Treadmills are designed to absorb some of the shock that happens when people run. This takes some of the strain off joints but it also prevents the body from triggering processes that ultimately lead to better bone density. Running outside can help runners improve their bone health which is especially useful for female runners or runners over a certain age.

Stronger Mental Health Benefits

Running boosts mental health. There are a couple of reasons for this, some of which rely on chemicals the body produces during exercise. But some of the reasons are more straight-forward. Exposure to fresh air and sunlight are proven mood-boosters for most people. Running gives athletes access to both. Runners can also “lose” their thoughts for a little while as they focus on their surroundings, their breathing, and their form. None of these factors can be replicated on the average treadmill, giving outdoor running a leg-up.

The Cons

Outdoor running does have its downsides, however. Some are obvious and immediate while others take longer to notice. In these instances, moving indoors might be a runner’s best bet.

Health Concerns

Certain conditions, injuries, and illnesses make it a bad idea to run outside vs on a treadmill. Pregnant women may find running indoors easier as they are more easily dehydrated and overheated. Injured runners will also find it easier to practice recovery runs inside where they can more easily control the terrain. And anyone recovering from a long illness is better off on a treadmill where they can run without worrying about a return trip.

Safety Concerns

Some runners don’t live near accessible and safe places to run. Other runners may not feel comfortable running at night or during high-traffic times. These runners are better off running inside than not running at all.

Undesirable Terrain

If a runner wants to run hills but lives in a very flat area, treadmills allow them to simulate hills. And if a runner lives in a hilly area and needs a lot of flat space, a treadmill can let them practice speed sprints without tracking down a dedicated outdoor space. The machine cannot perfectly replicate the outdoor experience, but it is better than missing out on training altogether.

Running on a Treadmill Vs Running Outside

The Pros

While outdoor running may be the most popular image for runners, there is a reason treadmills dominate so many gyms. There are upsides and even benefits to hitting the belt now and then.

Controlled Environment

The most obvious benefit to running on a treadmill is the control it offers. Indoor runners will never be rained out, too cold, or dangerously warm. Their water is always close at hand and they can run to exhaustion without worrying about a return run. This is especially helpful in places where temperatures can go to extremes at either end of the thermometer and might make outdoor running uncomfortable or even dangerous.

More Easily Tracked

Treadmills track most run statistics on their own. The runner’s speed, the distance they’ve gone, and – in some cases – even an estimate of the calories burned. These numbers are even more accurate when combined with a motion tracker like a Fitbit, allowing the runner much more control over the effort they exert. It also allows runners to track their progress and milestones more aggressively. This can make it easier for new runners to motivate themselves and injured runners get back on their feet.

Safer for Certain Runners

Certain runners do not feel safe running outdoors. These runners may only be able to run after dark or during high-traffic times. Other runners may worry about running along outside and requiring assistance that is not available. Whatever their reason, these runners are best suited to tracks and treadmills. This provides them with most of the benefits of running but removes the dangerous elements that may worry them.

Easier on Joints

Treadmills are designed to reduce the strain on a runner’s joints. This is excellent news for runners who may be recovering from an injury or want to give their joints a break. Some studies even suggest that using a treadmill once or twice a week prolongs the health of a runner’s joints.

The Cons

Treadmills do have their downsides, though fewer than their opponents usually suggest.

Less Energy Burned

Treadmills burn less of a runner’s energy. The difference can be reduced by setting the machine at a minimum of 1% incline, but there will still be a difference. Researchers believe the difference comes down to wind resistance, obstacles, and how the runner propels themselves. Treadmills feed the “ground” to the runner, whereas runners have to grip the ground and then push off when they run outside.

May Shorten Strides

Multiple studies have shown that treadmills do not ruin a runner’s form. Taller runners, however, may find their strides shortened on an average treadmill. This may be fixed by running on a longer belt. A runner’s best bet, however, is to alternate between machine running and outdoor running. This will avoid damage to their stride length and still give them the benefits of indoor running.

Fewer Health Boosts

It has already been established that running can help boost a person’s mental health. Unfortunately,  running on a treadmill does not give the same boost as running outside. Researchers aren’t completely sure why, but they have a few ideas. Indoor running does not provide the fresh air and sunlight of outdoor running. Running indoors also does not provide the same distractions as running outside. This lack of distractions may leave runners in the “thought loop” that characterizes many kinds of depression and anxiety.


In the end, it is up to each runner to decide whether they should opt for a treadmill vs running outside. Most experts agree that runners should use both, alternating between whichever option suits them best day by day. Strength training, a combination of environments, and regular rest days seem to be a runner’s winning combination.

Be sure to check out our article on Treadmill VS Exercise Bike too.


  1. Runners World
  2. GQ
  3. Shape