The 1% Incline: Simulating Over-Ground Running?

Are you part of the 1% club? No, we don’t mean the wealthiest group of Americans or an outlaw motorcycle gang (although, you may be part of these groups too - the treadmill really is for everyone.) But what we mean is are you a runner that increases the incline of your treadmill to 1% to better simulate over-ground running?

If yes, were you also told that this was incorrect? Or that you should just try running faster or that you should just bag the treadmill altogether?

We are here with a little help from Cory Hofmann of our own Cybex Research Institute to tell you why you may not necessarily be wrong, nor are your friends when they tell you to just run faster.

Does 1% incline simulate over-ground running?

So does running at a 1% incline on a treadmill really simulate over-ground running?

The answer: sort of. Cody Beals, a pro triathlete and self proclaimed exercise nerd, uses physics to attempt to explain what differences, if any, occur when running over ground vs. treadmill running. Specifically, he shows the differences in drag, or air resistance, when outside vs. inside.

While Beals admits his model is simplified to account for runners who weigh an average of 150 lbs. running at sea level in conditions that are similar to what you would find indoors, the model does suggest that the 1-2% incline rule of thumb is a reasonable approximation of the energy output you would expend when running outdoors. But this is for runners who are traveling at speeds greater than 10 mph (which translates to a 6 minute mile or better). This is also consistent with several research studies, which have been summarized by the CRI’s Dr. Paul Juris.

I don’t know about you, but I will not be running at a constant speed of 10 mph anytime soon. If you are like me (and that is more than okay), then the 1-2% include rule is probably overdoing it a bit.

CRI's View of 1% Incline on a Treadmill

Our own Cory Hofmann weighs in on the 1% rule and why you should consider making this tweak (or not) to your treadmill settings:

The 1% rule appears to be valid for fast running speeds if the intention is to create comparable caloric expenditure, but be aware that there are biomechanical differences between running on an incline and running on level ground. Even though the rule is exaggerated at slower speeds, if one is entirely able and capable, then there is no harm in working slightly harder by increasing the incline.

What about just going a little faster on the treadmill?

As for increasing our speed a little (say by 3-6%) as another way to simulate over ground running, Beals also developed a model to account for this. Again, he simplified for things such as runner size and environmental conditions, but the results still show that these adjustments work well for those of us who run pretty fast anyway. This time, it is a little more forgiving though, as his results show that increasing your speed by 3%-6%, a difference of about 12-18 seconds per mile (depending on how fast or slow you run), offers the most over ground running equivalency for those who run between a 4:50 – 8:00 min. mile (or roughly 7.5 – 12.41 mph). Here are Beals' results:

If you run faster than this (and if your name is Meb Keflezighi), you will have to increase your speed much more to simulate running outside. Here is a helpful chart that illustrates how much faster you may need to run on a treadmill based on your typical mile pace:

If you run slower than this, increasing your speed slightly won’t necessarily simulate over ground running, but any increase in speed over distance will help you along your way to becoming a stronger runner.

Increase Your Speed 3-6% on the Treadmill

According to Cory Hofmann, increasing your speed 3-6% on a treadmill can be a great idea:

If you are running to burn calories, then of course running a little bit faster will be better! If you are training and using the treadmill to stay at an easy-pace, then simply run based on your effort level rather than the speed on the treadmill.

Treadmill Incline vs. Running Speed

Really there is no clear answer here, but it is nice to know that you have the option to perform either adjustment (or neither), without altering the workout too much or making it much more difficult than what you are used to. If you want to try making these changes to your treadmill workouts, make your choice based on your exercise goals and what you think you are capable of.

Inclined running increases the muscular demand, especially in the calves, so consider this when deciding on incorporating inclines into your treadmill workout. Faster runners or those performing a speed workout might consider a slight incline or increase in speed when considering their workout goals/times.

According to Cory, “If the goal of the exercise is to simply burn more calories, working at a higher intensity (longer, faster, or higher incline) will be beneficial. Ultimately, the differences are so small between running outside and on the treadmill that it shouldn’t be a concern. If the goal is to compare outdoor miles to indoor miles, they are close enough. But if this misconception is enough motivation for someone to run slightly faster or at a slightly higher incline, then go for it!”

That said, logging some quality time burning some calories is never a bad thing, if you are indoors on your treadmill or on the open road. There are plenty of reasons to enjoy both treadmill and outdoor cardio this winter, so get out there (or indoors on one of our treadmills) and start moving.