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Ask The Experts: Why Am I Slower Outdoors Than On A Treadmill?


Dear Experts,

Last year I weighed in at 274 lbs, was on beta blockers, and had numerous issues with my knees and shoulders. Since September of last year, I have been training regularly, and have made some great strides, including finishing the Rock ‘n’ Roll Chicago ½ Marathon in 2 hours, 45 minutes and 45 seconds.  In addition, I now weigh 193 lbs, and I no longer need to take the beta blockers.

Anyway, a majority of my running is on a treadmill. I am not, and I do not ever expect to be, a fast runner. But I think that I can keep a respectable pace on the treadmill. I am able to do my workouts (all but my long runs) with an average pace of 5.7 [mph] on the treadmill, and I hit sustained speeds of 6.2 [mph] for 5 minutes. What I am having a hard time doing is transitioning to running outside. My outside running times are significantly slower, and as a result, I seem to tire out much more quickly. I can run for an hour and a half straight on the treadmill (and longer), but there are times when I run outside that I can’t run for 40 minutes straight.

So how is it that I can make that transition? And how should I pace myself? Should I find a pace on the treadmill, and get used to that pace, and then attempt to do that outside? I will be running the Rock ‘n’ Roll ½ Marathon in Vegas in December, and I really want to be able to break the 2 hour and 30 minute time.



Dear Greg,

First of all, congratulations on your weight loss and health improvements. That’s fantastic.

Now, to your question. The relationship between treadmill and outdoor running is an interesting one. Although the action is fundamentally the same in both environments, on the level of details there are some key differences between outdoor and treadmill running. Most notably, in outdoor running, forward motion is achieved through the application of force from the foot to the ground. On the treadmill, of course, there is no forward motion. Instead, a runner keeps from moving backward with the belt by applying force to the belt with the foot so as to continually reposition the foot underneath his nonmoving center of gravity. Other differences between treadmill and outdoor running include the absence of wind resistance indoors and a softer, more pliant landing surface in the case of the treadmill.

Whether treadmill or outdoor running is “easier” than the other is a matter that has been much debated. In my opinion, the evidence shows rather plainly that while treadmill running is in fact easier, outdoor running is faster. Research has shown that heart rate is slightly lower at any given pace on a treadmill than it is outdoors. However, in one study by researchers at the University of Stockholm, runners were allowed to set their own pace in an indoor treadmill run and an outdoor trail run. They ran significantly faster at the same perceived effort level outdoors.

These findings only seem contradictory if you overestimate the importance of heart rate, as many runners do. Bear in mind that the winner of any given race is usually the runner who has the highest average heart rate throughout it. This is simply an indication that he is the runner who is able to work the hardest over the full race distance. Thus, while treadmill running may be more efficient than outdoor running, such that heart rate is slightly lower on the treadmill at any given pace, something about the treadmill limits how hard a runner is able to work relative to outdoors.

One possible factor is emotional in nature. Most runners find running outside more fun and stimulating, and this may enable harder work. Another possible factor is neuromuscular. When you run on a treadmill, you are locked into a very rigid rhythm, whereas outdoors there is all kinds of subtle variation in rhythm and movement patterns from one stride to the next. I have a strong suspicion that, by leaving more control in the hands of the runner’s nervous system and allowing such subtle play in the stride, the outdoor environment enables the runner to run more relaxed and effectively. But that’s just speculation.

So, I’ve just explained why runners run faster outdoors than indoors, and yet your personal experience is just the opposite. How can that be? There are three possible reasons for your being an exception to the rule. First, as you’ve stated, you do most of your running on a treadmill, so you’re currently better adapted to it—that’s the principle of specificity at work. Second, you’ve identified yourself as a heavier runner, and as such, you may be able to run more comfortably and with less abuse to your legs on a treadmill, thanks to its softer, more pliant landing surface. And finally, while most runners enjoy outdoor running more than treadmill running, some do have the reverse preference. Perhaps you currently enjoy treadmill running more and therefore put more into it.

Regardless, road races take place outdoors, and to meet your road racing goals you need to be well adapted to outdoor running. So here’s what I suggest:

  • First, spend more time running outside. The more you do it, the more comfortable and proficient you will become.
  • Second, do as much of your outdoor running as possible on softer surfaces such as grass and dirt instead of asphalt and concrete. This will help you run more comfortably outdoors and ease the transition.
  • Third, ignore pace and run by feel outdoors. Instead of trying to duplicate the pace of your treadmill runs outdoors, try only to duplicate the duration and effort level, even if that means you have to run ridiculously slowly at times. Just don’t worry about your outdoor running pace for now and concentrate on the process.

I can guarantee that with a little patience and persistence you will steadily improve as an outdoor runner until you are able to run just as well outdoors as you are on the treadmill—or better.


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