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The GOOD and BAD of Treadmill Running


It’s that time of year.


It’s cold outside. Wet. Snowy. Icy. Windy. Dark. Quiet…


And you’re registered for a spring marathon.


Ha! Good luck!


…just kidding. But in all seriousness. What do you do when you’re about 4-6 months away from a huge event this time of year? You don’t have many options, to be honest. Run outside in any or all of the conditions listed above…or run on a treadmill.


Most people choose to run on a treadmill if they have the access. By “access” I mean if they “own” one. I’d go out on a limb and say 99% of people training for races have some sort of gym membership. So sure, of course you have access. But driving to the gym in these conditions also has it’s limitations. First of all, if you want to run EARLY, you might not be able to. You probably need to wait until 6am when the gym opens. For those of you who like running earlier than that, your hands are tied! Not to mention, the gym requires significantly more preparation compared to running on a treadmill you own. Get stuff ready, warm the car up because it’s been sitting outside in the elements overnight, prepare your gym bag, prepare a shower bag, prepare your fuel/supplements, etc. etc. I own a treadmill and all I do is put my sneakers on, walk downstairs, and go. It’s pretty awesome. Any time of day, too, which is a huge plus.


This time of the season comes around and I typically always find myself on the treadmill. I’m not saying it’s either GOOD or BAD…but I’ll provide some feedback I’ve experienced lately, and you can be the judge.



Pacing is KEY for big marathon preps. Race pace, tempo runs, tempo intervals, sprints, long slow distance runs, anaerobic intervals…all of these can be controlled on the treadmill very easily. You can kind of FORCE yourself to adhere to your program a bit better by seeing your pacing. When you’re outside, you may have a goal in mind, but it’s up to you to move your body at the appropriate pace to get the specific adaptation from the session. The treadmill does the work for you. If you’re running a tempo run at 20 seconds faster than your marathon pace, you can be guaranteed (if it’s calibrated correctly) that the treadmill will stay at that pace the entire run. If you’re attempting to run a long slow distance (LSD) run on the treadmill (I do NOT advise this), you can easily select pacing that falls within the 2-2:30 SLOWER (yes, you read that right) pace that’s required (I’ll dive into that relevance another time).



Temperature is also important when you’re running for awhile. If you’re running outdoors in 90+ degrees, your fueling changes. You prepare differently when you’re in different climates. At least, you should. When you’re running on the treadmill, you can also use a fan! If your pain cave is super hot and humid, crank that fan and get some airflow! The temperature greatly influences your pacing as well. If the temperature is very hot outdoors, you are FORCED to slow your planned pacing. I once raced in a marathon that used colors to indicate the severity of the temperature. It was so hot and humid that it was recommended athletes should reduce their planned marathon pacing per mile by 90 seconds…what marathoner you know would drop their overall goal time by 40 minutes?! NONE. Needless to say, lots of athletes hit the wall very early and completely bonked in that race. I was one of them. But the same concern should exist when the weather is COLD outside! Your thermoregulatory responses CHANGE in different temperatures. It’s good to “practice” what you feel like and how you should fuel if you’re racing in cold or warm temperatures. Everything changes when you get off the treadmill.



This is a curious one, but relevant in my opinion. Let’s keep it simple. If you’re indoor on a treadmill, you can wear less clothing because the climate is controlled (see above). But if you’re running outside this time of year, you are bundling up! This IMMEDIATELY raises your skin, core, and total body temperature. Without diving into the physiology, all three of those metrics matter. Yes, the cooler outdoor temperatures will surely prevent you from overheating, perhaps. BUT you will likely start sweating faster due to the microenvironment created by skin and clothing contact. Just a thought…it may not negatively impact your run, HR, performance, etc. but it’s certainly something to be mindful of. Because again, if your temperature and/or thermoregulatory responses are altered, your fueling should also likely change.



This is an easy one. Treadmill has no distractions. Outside running has a lot of distractions. Due to the required awareness of outside running, it’s possible that you’re expending more energy simply by focusing a bit more (mentally, and also your running gait, avoiding potholes, skipping over sidewalks, running off the road if a car passes, etc. etc. – this all burns extra energy and requires mental focus). This is both good and bad. You’re expending more energy, yes. Perhaps that’s good in terms of caloric burn. But it’s NOT good in terms of running economy. Running economy refers to metabolic cost at a given intensity or pace. In simplest terms, if you’re running at an 8:00min/mile pace on a treadmill for 10 miles, let’s say your HR is 130bpm. Now let’s take the 10 miles at 8:00min/mile outside instead of the treadmill. You’re wearing sweats, winter hat, gloves, it’s rainy and dark so you have a headlamp, you’re dodging cars as they pass, and jumping over sidewalk edges…your HR may jump to 145 for the duration of that run, at the (alleged) SAME intensity. Make sense? This is avoided by running indoor on a treadmill. BUT running without distractions isn’t really practical, is it? I mean, when you’re racing, you absolutely will have to deal with some of those distractions. The treadmill does NOT prepare you for dealing with those distractions, and may, in fact, provide you with a false sense of efficiency at given speeds.



This is one that certainly favors road running, in my opinion. The treadmill may have some advantages related to some of the items that you can “control,” but in terms of injuries, there are some specific negatives associated with the treadmill it’s important to be aware of. First of all, when you’re running outside, sure there’s the potential for injury. These potential injuries are related to stress, excessive volume, maybe tripping over something, vehicles, etc. But on the treadmill, the interaction between shoe and belt isn’t favorable for the hip/knee/ankle/foot. The impact is high. Higher than outdoors; almost like a pounding that can become dangerous if too much volume is on the treadmill (sure, this also depends on body weight). But hip/knee/ankle stress is high on a treadmill. The potential for overuse injuries is a bit higher here. Theres also the obvious potential to fall off the treadmill! Again, if you’re too distracted with Netflix or not paying attention…BOOM. There goes the season. Lastly, damage to the bottom of the foot, or some form of plantar fasciitis can occur. Damage to the deep tissue is possible due to the excess stress. This also depends on the shoe you’re wearing and your efficiency with each foot contact. Talk to a professional if this is overwhelming!


In summary, I’m not really sure what’s “BETTER” this time of year. I know the treadmill has some benefits. I know running outdoor has some benefits. Both can absolutely be used, and I think you SHOULD incorporate both at different times for different reasons, especially this time of year.


Please feel free to reach out if you have any questions about any of this! And share your thoughts, too. Which do YOU think is best???