When Should You Run vs. Hike in an Ultramarathon?

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When Should You Run vs. Hike in an Ultramarathon?

Should you run vs. hike up a steep grade during a trail run or ultramarathon? Does the run vs. hike decision hinge on the steepness of the grade, the duration/distance of the climb, or the speed of the runner?  Turns out, the best answer from researchers, coaches, and athletes is that the run-to-hike transition point depends on all of the above. So, let’s look at the science of traveling uphill so you can figure out when you should switch from running to hiking.

How Can We Tell Whether It’s Better To Run vs. Hike Uphill?

First, we must figure out what we’re trying to achieve. Based on the research that’s been done on uphill running, choices include:

• Maximize running economy: To maximize running economy, you want to minimize the oxygen cost of locomotion, or use the least amount of oxygen to go as fast as possible.
• Finish faster: This applies to finishing the climb itself faster as well as reaching the event finish line faster.
• Reduce fatigue/muscle damage: Delaying the onset of fatigue and muscle damage helps trail runners maintain a faster average pace longer into an ultramarathon.

Running Economy in Uphill Running vs. Uphill Hiking

At some point during an uphill climb, it may be more economical (i.e., use less oxygen at a given pace) to hike/walk instead of run. To figure out the optimal grade vs. pace combination for this transition, we first must explain running economy on level ground.

When do people switch from walking to running on flat ground?

Researchers have studied the oxygen cost of transport in walkers and runners for decades. When you plot walking speed against cost of transport on flat ground, you get a clean U-shaped curve. The speed at the bottom is the cheapest, metabolically, and speeds faster or slower than that cost you more oxygen per meter covered.

The most economical walking pace is around 1.5-1.6 meters per second (approximately 16:45-18:00 minutes per mile). The curve above stays relatively constant across most populations, athlete and non-athlete alike, in countries and cultures worldwide. It’s important to note, too, that although “preferred walking speed” and “most economical walking speed” are not synonymous, they align closely enough that researchers consider preferred walking speed as a proxy for physiology behind it.

On flat ground, people naturally shift from walking to running at about 2 meters per second, about a 13:30 minutes per mile pace. And physiologically, that’s about where running becomes metabolically cheaper, too. Humans have evolved/adapted to make the walk-to-run transition when it becomes metabolically too costly to continue walking.

The figure below represents these two points (the bottom part of the U-shaped curve is the preferred walking speed and the intersection of the blue and black lines is the preferred walk to run transition under level conditions).

 

 

Running vs. Hiking on Steep Grades

To assess when to run and when to walk in steeper conditions, researchers from the University of Colorado Integrative Physiology Department brought tested high caliber runners at different speeds at a 30 degree slope (or 58% grade). For context, a 30-degree slope is steeper than the infamous Manitou Incline and about equal to the slope of the vertical kilometer course in Fully, Switzerland where the current VK world record stands.

Along with the metabolic data, they also collected EMG information to see how their muscles were working under those different conditions. Metabolically, all runners were more economical at speeds below .9 m/s (just under 30-minute miles). Meaning, on something ridiculously steep, all but the very best runners at the very highest speeds will be more economical walking vs. running.

Earlier data from 2015 (see Figure 3 below) showed that when vertical speed is kept constant, walking is more economical across a range of speeds and grades, with exception for the trial that was done at a 10 degree slope (18% grade) at a speed of 2.14 m/s. To put that into context, that’s running a 12:30 min/mile pace up the back side of Hope Pass on the Leadville 100 course (which is slightly less than a 18% grade).

 

Taken together, the research above indicates that running is only more economical than walking for some elite runners on the steepest of climbs. When the trail is steep, almost everyone is better off hiking.

Hiking Is Not Necessarily Easier Than Running Uphill

We need to dispel the idea that hiking/walking on steep hills is “taking the easy way out”. Just because walking/hiking is more economical on steep grades doesn’t mean it’s easy, especially compared with traveling over flat ground. When researchers investigated muscle activation directly, walking up a modest nine-degree incline drove dramatic increases in muscle activity throughout the leg, compared to flat ground. The hip extensors worked several times harder. The quadriceps and calf muscles worked substantially harder too. And as walking speed increased, muscle activation climbed as well.

Another difference between walking and running is the spring-like action of your Achilles tendon. When running, particularly on flat ground, the Achilles stores energy on landing and returns a significant portion of that elastic energy when you push off. When running uphill, you benefit less from the stiffness of your Achilles tendon, and that benefit largely breaks down once you’re walking uphill.

So, even though walking up a steep grade is the more economical choice from an oxygen standpoint, it still places significant mechanical demand on leg muscles and largely excludes any potential energy return from a stiff Achilles tendon. Hiking a climb is not necessarily an easy option for your legs. You’re choosing a different loading pattern, not a lighter one.

Practical Recommendations for Run vs. Hike Transition

Currently, there is no table nor piece of software that will reliably recommend the optimal speed/pace for every athlete’s run-to-walk transition across a range of grades. We know that a good run to walk transition point on flat ground is ~18:00 min miles. Meaning, if you are walking faster than that on flat ground, it’s more economical (costs less oxygen) to run. If you are running slower than that, it’s more economical to walk.

When it comes to trail running and ultramarathons, the list below includes practical recommendations for ultrarunners at the front to the back of the pack:

1. Practice walking in training. This is something I don’t think enough runners do. Particularly with the longer ultras with more elevation gain, walking is going to be a big part of your race plan. Just like nutrition, gear, etc., better practice it in training. So, if you have climbs available to you, it might make more sense to dial down the intensity and hike them in training, even though you run them if you wanted to.
2. Use RPE during the race to determine when you are going to hike and when you are going to run. You should have a reasonable RPE plan going into any race. When executing that plan, hike when your RPE is getting too high (and hike slower if you need to) and run when you can keep your RPE in your desired range. Simple, but not easy!
3. If you are ever in-between a hike and a run, hike if the race or the particular climb is longer and run if the race/climb is shorter. With the shorter climbs and/or races, you can take a bit of risk and run slightly harder during the uphill, knowing that there (likely) is a downhill on the other side where you can recover.

Special Thanks

Special thanks to Jackson Brill for his contributions to this article. 

References 

1. 1. Characteristics of Preferred Gait Patterns: Considerations for Exercise Prescription – Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Representation-of-the-metabolic-cost-of-transport-COT-for-walking-and-running-as-a_fig2_294873908
   2. Ortiz ALR, Giovanelli N, Kram R. The metabolic costs of walking and running up a 30-degree incline: implications for vertical kilometer foot races. Eur J Appl Physiol. 2017 Sep;117(9) 1869-1876.
   3. Giovanelli, N, Ortiz A, Henninger K, Kram R. Energetics of vertical kilometer foot races; is steeper cheaper? Journal of Applied Physiology. Feb 2016.
   4. Minetti, A. E., Moia, C., Roi, G. S., Susta, D., & Ferretti, G. (2002). Energy cost of walking and running at extreme uphill and downhill slopes. Journal of applied physiology (Bethesda, Md. : 1985), 93(3), 1039–1046.