Can you compare indoor lab tests with outdoor field test?

The comprehensive results of a complete physiological assessment can help you to plan your training sessions and nutrition more effectively. It’s a necessity for elite runners and it’s even a good idea for recreational runners that are training for a specific time in an upcoming event.


But where should you test? Should you seek out your local sports science performance lab? Or should you implement field test protocols to measure your performance data outdoors? The truth is, there are variables that will affect your performance data whichever method you choose.


So, we’re going to break down the pros and cons of testing running protocols indoors vs outdoors. This will enable you to understand your performance data in more detail and will give you an informed view of the limitations caused by the test setting.

The benefits of indoor lab tests

Let’s start by taking a look at some of the benefits of testing indoors. It’s often the go-to setting for elite athletes looking to gather data on their VO2max, running economy, lactate threshold, substrate utilization and other useful data. But why is that?

Indoor lab tests provide access to advanced testing equipment

Probably one of the most obvious benefits to indoor testing is that performance labs will house all of the advanced testing equipment that can’t be taken outdoors. For example, if you were looking to measure your metabolic efficiency you need a gas exchange mask which is hooked up to a metabolic cart and to a computer. So, it’s simple to understand why it’s easier to test your metabolic efficiency on a treadmill rather than on an athletics track.


Testing indoors is in many cases the only way that athletes can access all of the equipment necessary to gather data from the most basic test protocols, to the most advanced protocols.

Whether in cycling, running or any other sport: tests are often performed indoor, mainly due to the needed equipment

Indoor lab testing controls for major variables

Indoor testing allows for tighter controls over variables that will affect your performance. For example, two of the biggest factors that can skew your data when testing outdoors are wind drag and inclining/declining terrain. Running indoors on a treadmill can eliminate those two variables immediately and ensure that your running performance is not tainted by variables outside of your control. So, in that sense, your performance data is more accurate.


Controlling for variables also comes in handy when collecting measurements during step tests. When measuring your running performance, your coach or lab technician will usually have you execute incremental step tests that start at a low intensity for a set period of time and increase in intensity across intervals of the same set time. This is easy when testing indoors on a treadmill because your location stays the same. So, if lactic samples need to be taken or your heart rate needs to be measured, you are right next to the person recording this data. This is in contrast to testing outdoors, where it is difficult to measure during step tests because the distance travelled and therefore location differs when intensity increases.

The benefits of outdoor field testing

We’ve discovered that testing indoors is the go-to setting to measure some of the most important running performance metrics. The tighter control over variables like drag and access to lots of advanced equipment suggests that indoors could be the best place to test. So, why would anyone want to test outdoors?

What are the benefits of field tests over indoor lab test?

Field-test protocols allow you to test closer to race day conditions

Replicating race day conditions when running test protocols is much easier to achieve when you are testing outside. This is because the event you are training for is likely to be held on a track, road or trail. The feedback your muscles get when pounding a treadmill is significantly different to running on a road for example, and it requires a different energy demand. This difference could affect your scores when measuring things like your VO2max or anaerobic threshold. So, it’s difficult to accurately extrapolate the data gathered from running on a treadmill indoors to calibrate your outdoor training sessions.

When you carry out test protocols outdoors, you can perform them on terrain that matches the conditions that you will experience on race day. For marathon runners, understanding your anaerobic threshold or FTP over tarmac will allow you to plan your training sessions more accurately than if you were to work it out from data gathered from treadmill running. The same applies to track and trail runners.

The main difference between indoor vs outdoor running

You might wonder if indoor (treadmill) running is truly different from outdoor running. Let’s find out.

When running outdoor, the most efficient runners will have a small vertical lift and will exert as much force as possible across the horizontal (or forward) plane of motion. Runners that have a 10cm vertical lift compared with runners that have a 5cm vertical lift when travelling overground are effectively increasing energy demand. However, they will not increase the distance travelled across the horizontal plane. Which is the ultimate goal of running. So, there is an incentive to decrease vertical lift so that more energy is directed to forward motion when running overground.

The same theory does not apply when running on a treadmill. A runner with a higher vertical lift in their stride will theoretically have to exert less energy on a treadmill to cover a set distance than those with a lower vertical lift. As the runner is experiencing hang time between strides, the treadmill is still moving at the same speed. The distance travelled between each stride will be more for runners with a higher vertical lift. Therefore, requiring them to exert less energy over a fixed distance.

This challenges the idea that data collected indoors on a treadmill can be extrapolated to outdoor conditions. It also confirms the benefit of testing outdoor when training and racing outdoor.

Final thoughts

We’ve highlighted that indoor testing is great for measuring all the protocols that you need to create an effective training plan. However, the indoor lab setting and running on a treadmill does not replicate a real-life setting and therefore the data doesn’t accurately represent your true performance metrics.


Outdoor testing allows you to create testing conditions that are similar to the conditions in which you need to perform on race day. However, you cannot measure all of the data that you would want to know as an athlete training for a big event.


In an ideal world, we could take the necessary equipment outside to accurately determine our bodies metabolic efficiency in similar conditions to the event we are training for. Is this possible? Sure. However, the cost of portable gas exchange systems used to measure metabolic efficiency will make your eyes water. So, for most of us, this is simply not possible.

Do we really need to continue dreaming of an ideal world where we can run indoor testing protocols in an outdoor setting?

Future Technology

Tero Joutsen is an exercise physiologist at the Finnish KIHI Research Institute for Olympic Sports. He carried out an undercover test that measured the INSCYD Power-Performance Decoder’s ability to measure VO2max and metabolic efficiency outdoors while cycling. He then compared it with gold-standard lab test results. He found that his outdoor test results from INSCYD’s Power-Performance Decoder, were identical to his lab results.

If only there was a similar test that gave running coaches and athletes an affordable, non-invasive field-testing protocol that could accurately measure VO2max, metabolic efficiency and more… But there is! Read about that test by clicking on this link.