Hello,
Reading this post about UTMB made me think about this C. Weller's post on Instagram about running / walking in function of the slope. Below is the copy-paste:
When you're trying to move quickly in the mountains over long distances, it can be tough to decide the right points at which to switch between running and walking.
On flat ground, this is easy enough. It's dependent on speed. At slow speeds, walking is more efficient. At higher speeds, running is more efficient. (this is why race walking is so weirdly exhausting - it'd be easier to just run at that pace)
If you're measuring biomechanical efficiency, we tend to transition from walking to running a little bit early on flat ground. Most people find it more comfortable to start running or "shuffling" just a little earlier than is functionally necessary.
This changes when the terrain goes from flat to uphill.
At some point, no matter how quickly you're trying to move, walking becomes the fastest, most efficient way to get up a long hill. You could try running, but you end up putting more energy into going the same speed or slower, and wearing yourself out.
The point at which we naturally figure out this transition is on slopes of about 15 degrees or more. Once hills are that steep, most people instinctively revert to a purposeful walk, even when trying to move fast. On hills lower than 15 degrees, we're likely to still want to switch to running earlier than is necessary. There is an awkward transition point where neither mode of travel feels quite right. Walking is too slow, but running seems unnecessarily fatiguing.
Researchers have also found that in variable and steep terrain people tend to do best with an alternating approach between running and walking. Aside from the variability introduced by natural changes in the slope, this is a way of allowing for alternating recovery.
The soleus muscles (part of your calves) have been shown to do 36% less work when running uphill rather than walking. Running switches the demand to other leg muscles and the aerobic system.
By periodically switching back and forth between running and walking, you're able to let your calves recover from walking, and then let your hips, quads, and aerobic system recover from running. "
Kind regards,
Pet'