Treadmill Running: What’s Grade Got To Do With It?

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In researching treadmill running, I’ve come across three items where there has been an attempt at quantifying what an effort is based on the treadmill speed and grade. The first was simple: For every 1 percent increase in grade, your effort was equal to 0.2 mph higher on the speed. So, for instance, if you were running at 8 mph and 1 percent grade, it would be equal to running at 8.2 mph at a zero percent grade. Pretty simple, and if I knew how this conclusion was reached, the more likely I would be to believe it.

The second is a very popular chart from the website HillRunner.com. I had actually referred a number of my athletes to this chart. However, the more I looked into it, the more I pondered how accurate it was, especially at faster speeds. After trying it out for a workout of my own, the more I thought that there was no way that I needed to put the grade that high to hit these paces. Again, I wish there was an explanation behind the theory that would help me better understand it.

Finally, there’s always Jack Daniels, the solution to any situation that calls for data or a strong drink. (Yes, that was a very bad joke. How many times do you think he’s heard that in his 82 years of life?) Anyway, I actually opened up a book and took a look at his charts. Now, I immediately noticed the following:

1. How much faster the equivalencies were compared to the Hill Runner charts

2. That he incorporated VO2 into the charts. (For your reference, this is tables 4.5 and 4.6 of the latest edition of Daniels’ Running Formula).

Why is this important? Because at any given speed and grade, we can calculate the VO2 cost, or how much oxygen is required to run at that speed and/or grade. So, after calculating the VO2 cost of a certain pace with no grade, you can then correlate and adjust the variables (speed and grade) to find what equal work is for whatever variables you plug in. Here’s what I mean:

The following is a formula for running from the American College of Sports Medicine:

VO2 (mL . kg-1 . min-1) = (0.2 . S) + (0.9 . S . G) + 3.5 mL. kg-1.min-1

S= speed in meters per minute

G = grade, expressed as a fraction

Without getting too technical, you can start by calculating what the VO2 cost is for any flat run by taking the mph and converting it to meters per minute (1 mph = 26.82240 m/min) and tossing that in for S. Then just replace G with a zero and run the numbers. You could then find the VO2 cost for the pace you’d like to hit by then either figuring out the actual speed you want to run (solving for G) or solve for S by putting in the max grade you want to run. The result is a good indicator of what kind of effort you are putting in on the treadmill, given your pace and incline.

So is this exact? Probably not. The only way it would truly be completely accurate is hooking yourself up to a metabolic cart for every run, and that’s no fun. However, if you are just trying to get the work in, this is a great way to be pretty darn close to where you need to be for the workout.

Going back to Daniels, I found a messageboard thread in which he contributed, stating that he looked at Boston Marathon splits and also did another study in which he found the ratio to be 12-15 seconds slower per 1 percent grade incline. One caveat here that wasn’t made crystal clear—it appeared he was talking about some pretty quick runners, because he referenced overground running of 5:00-6:00 minute-per-mile pace. I also found another reference from Tim Noakes, author of Lore of Running, that gave a number of 2.6 ml/kg/min (amount of oxygen) increase per 1 percent increase in grade. This then translated into a reduction in speed of around 0.65 kilometers per hour. So, comparing the numbers, Daniels and Noakes match up pretty well.

So, the natural turning point of this discussion turns to the question: “Do I need to run at an incline to compensate for the lack of a self-created headwind?” I have gone back and forth on this question. If you look at the chart from Hill Runner, it’s pretty clear that a 1 percent incline should be used but again, I don’t know where they got those calculations. Daniels’ chart is based on VO2, so it isn’t particularly necessary. However, he did write in the later pages that essentially a 2-percent grade makes up for the fact that you aren’t creating a headwind. So, you might think that adding an incline is absolutely necessary, but I don’t know if that’s the case. The reason is that if you aren’t creating a headwind on the hamster wheel, your ability to cool yourself off is then limited. The result is a slightly higher work rate, represented by a higher exercising heart rate. Now, if you cool yourself off with a fan, then you’ll probably need to adjust the grade to compensate for the increased cooling. Otherwise, I don’t know if a 2-percent grade increase is necessary. I have a feeling that it all ends up being a wash!

The other caveat here is that Daniels’ entire conversation was based around faster-paced running. Noakes also made comments about a speed of 18K/hour  (5:24/mi pace) being the sort of a threshold where the headwind was a major factor. Mainly, the point of all this is that the faster you are, the more likely you will be to have to add an incline to match what your overground efforts.

RELATED: 3 Kickass Treadmill Workouts To Get You Through Winter

Key Takeaways:

  • You can replicate much faster workloads by adjusting your grade and keeping the pace manageable.
  • For easy runs across the pace spectrum, adding a grade will offset the lack of a self-created headwind. A complete generalization would be 0.5 percent for 8:00/mi pace and slower, 1 percent for 6:30-7:30/mi pace, 1.5-2 percent for paces faster than 6:00/mi pace. However, most people will not be approaching those paces for easy runs.
  • For faster workouts, just use the speed/grade combo that you are looking for and just don’t worry about the wind effect—your head might explode.
  • Experiment with which combo works better for you. Some people will thrive better with higher grades and lower speeds, while others will do better with the opposite settings. Personally, I like a fairly moderate speed with a moderate grade. I would try to keep the grade under 7 percent as then your form can start to change due to the incline.

In Closing:

To close this out, there are options out there. Whether you are trying to simulate a hilly race course or just trying to find a way to get your faster Hansons Marathon Method work in, you can do it. The big component for me is that you can adjust these variables and still feel confident that you are getting the right effort in on the right days. If you liked the way I laid out how I would calculate effort based on speed and grade combos, you’re in luck! We’ve made a handy calculator based on the Noakes and Daniels references to help you dial in that work effort. You can sign up for the download on our website.

Luke Humphrey is the author of Hansons Marathon Method (Velopress) and head coach of Hansons Coaching Services. This post originally appeared here and was republished with permission. 

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