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=The Difference Between Running and Walking=
Running and walking are two different forms of movement. In running you either have one foot on the ground or both feet in the air; both feet are never on the ground at the same time. In contrast, when walking you either have one or both feet on the ground and never have both feet in the air. Sometimes people think that basic physics means that it should take the same energy to move a human over a given distance regardless of running or walking. However, both running and walking are quite inefficient, so most of the energy expended does not go to forward movement. This is most easily seen when you compare a runner with a cyclist; for the same effort, the cyclist will move far faster. This means that the energy cost of running and walking is mostly around how much energy is wasted in each form of movement. =Do You Burn More Calories Running or Walking?=Generally, the answer is that running burns more calories per mile than walking, but as is so often the case, the real answer is "it depends". * If you're running at a moderate pace, you burn more calories per mile and per hour than walking at a moderate pace. * If you're race walking, then you can burn more calories per mile than running. (Race walking here is faster than about 14:00 min/mile.) * The relative Calories per hour for race walking and running will depend on the exact paces. =Should You Run or Walk in an Ultramarathon?=The table below gives some insight into when you should run and when you should walk in an ultra. This table shows how the slope would change your pace if you keep the same effort (Calories per hour). The first column is the running pace on the flat, then each column shows the pace you would travel if you run or walk on various slopes. The table is based on the available research, and there are obviously some practical limitations that make some values unreasonable for most people. As noted above, it's more efficient to walk than to run on level ground, up to the natural transition pace of about 14:00 min/mile. What's surprising is that it is also more efficient to run than walk on uphill sections, even as the equivalent pace drops. So, if you're able to run at a 10:00 min/mile on the flat, you could go up a 10% grade with the same effort at 16:35 min/mile when running or 17:39 min/mile when walking. This seems rather bizarre when both paces are below the natural transition pace (see below), but when I tested this out I found to my surprise it appears to be true. That doesn't mean you should run up the hills, as walking may be a useful break and using different muscles may help with fatigue. In addition, unless you've practiced race walking technique it's unlikely you'll be able to efficiently hit the faster downhill walking paces, where you may be able to hit the downhill running pace. For example, if you're running a 10:00 min/mile pace on the level, you may be able to handle running the 5:59 min/mile pace down a 10% decline, but few people will be able to walk at a 7:28 min/mile pace down the same slope. So it may not make much difference if you take walking breaks uphill or on the level, but you don't want to take them on the downhill sections. (In the table below, I've used a blue font where the walking pace is faster than the equivalent running pace.)<include_PHP file="CalorieInc_EvenEffort"/>=The Effect of Incline=It's intuitively obvious that running or walking uphill is harder than level ground. It's also reasonably obvious that modest downhill slopes are easier than level ground, but as the slope increases so the difficulty becomes greater. Scientific research has supported and quantified this<ref name="Minetti-2002"/>, showing that the energy cost of walking or running is to lowest at about 10% decline. There is some evidence that the slope of minimum energy is independent of pace<ref name=" Minetti 1994"/>. This slope of minimum energy requirement seems to corresponds with the slope that neither requires pushing back for forward movement nor energy dissipation for braking<ref name="SnyderKram2012"/>. The two graphs below show the relationship between slope and the cost of walking/running as measured by a number of studies.{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"|- valign="top"|[[File:Energy cost of running.jpg|none|thumb|300px|The energy cost of running for various slopes.]]|[[File:Energy cost of walking.jpg|none|thumb|300px|The energy cost of walking for various slopes.]]|}There are a number of factors that could change these assumptions:* A study looked at the energy cost of uphill, level, and downhill running before and after a 65Km mountainous ultramarathon<ref name="VernilloSavoldelli2015"/>. After the race, the energy cost of uphill running was unchanged, but both level and downhill running were significantly harder by 8% (level) and 13% (downhill). These differences were greatest for the slowest runners and at least for the fastest runners.* A similar study of a rather more extreme 303 Km mountain ultramarathon found that the energy cost of uphill running and walking was lower after the race<ref name="VernilloSavoldelli2016"/>. This result is a little surprising, and it's unclear why runners would do better fatigued than fresh. (The study did not look at level or downhill running.)* I've found no research on the effect of training on the energy cost of running uphill or downhill. I would expect that downhill training would reduce the energy cost of downhill running.
=The Transition Between Running and Walking=
The energy required to run a given distance is the roughly the same regardless of pace. This is different to walking, where the energy required to walk a given distance generally goes up with pace. This means that at slow speeds, it costs less energy to walk than run, but as you go faster it becomes easier to run. When people are put on a [[Treadmill| treadmill ]] and the speed gradually increased, they will naturally transition from walking to running. This transition occurs at roughly the same speed for most people and is called the Preferred Transition Speed (PTS)<ref name="Rotstein-2005"/>. You can see this in the two graphs below. The graph on the left shows the energy expenditure over time, showing the energy required to walk goes up faster than for running. The graph on the right shows the cost per distance, with running staying constant and the cost of walking rising with pace. (It takes more energy to walk a distance very slowly, so the graph shows the low point which is the lowest energy cost to cover a distance.)
{| class="wikitable"
|- valign="top"
|[[File:Energy cost and transition Distance.jpg|right|thumb|300px|Energy cost over distance.]]
|}
=Calories Per Hour=
This table shows the number of Calories used per hour for a person weighing <include_PHP file="CalorieInc_ShowWeight"/>.
This table shows the number of Calories used to cover a <include_PHP file="CalorieInc_ShowDistanceUnits"/>for a person weighing <include_PHP file="CalorieInc_ShowWeight"/>.
<include_PHP file="CalorieInc_PerDistance"/>
=Training Status Effects=
The graph on the below shows that there are slight, non-significant differences between runners and active non-runners. This indicates that training does not change the transition speed, though it’s it's worth noting that the actual transition speed is slower than would be expected from the energy costs<ref name="Rotstein-2005"/>. Also note that the actual cost of running is not quite constant with speed, but actually goes down as you go faster.
[[File:Transition Runners.jpg|none|thumb|500px|The energy cost for runners and non-runners, showing the Preferred Transition Speed (PTS) and the Energetically Optimal Transition Speed (ETOS).]]
=Formula=
for those who like to create their own tables, below are the underlying formulas that I'm using. The cost of running (Cr<sub>i</sub>) and walking (Cw<sub>i</sub>) on a slope is given by these equations:
Cr<sub>i</sub> = 155.4i<sup>5</sup> - 30.4i<sup>4</sup> - 43.3i<sup>3</sup> + 46.3i<sup>2</sup> + 19.5i + 3.6
Cw<sub>i</sub> = 280.5i<sup>5</sup> - 58.7i<sup>4</sup>- 76.8i<sup>3</sup>+ 51.9i<sup>2</sup>2+ 19.6i + 2.5
Where i is the slope and the result I in Jules per Kg per Meter.
=References=
<references>
<ref name="Minetti-2002"> AE. Minetti, C. Moia, GS. Roi, D. Susta, G. Ferretti, Energy cost of walking and running at extreme uphill and downhill slopes., J Appl Physiol, volume 93, issue 3, pages 1039-46, Sep 2002, doi [http://dx.doi.org/10.1152/japplphysiol.01177.2001 10.1152/japplphysiol.01177.2001], PMID [http://www.ncbi.nlm.nih.gov/pubmed/12183501 12183501]</ref>
<ref name="Rotstein-2005"> A. Rotstein, O. Inbar, T. Berginsky, Y. Meckel, Preferred transition speed between walking and running: effects of training status., Med Sci Sports Exerc, volume 37, issue 11, pages 1864-70, Nov 2005, PMID [http://www.ncbi.nlm.nih.gov/pubmed/16286854 16286854]</ref>
<ref name="VernilloSavoldelli2015">Gianluca Vernillo, Aldo Savoldelli, Andrea Zignoli, Spyros Skafidas, Alessandro Fornasiero, Antonio La Torre, Lorenzo Bortolan, Barbara Pellegrini, Federico Schena, Energy cost and kinematics of level, uphill and downhill running: fatigue-induced changes after a mountain ultramarathon, Journal of Sports Sciences, volume 33, issue 19, 2015, pages 1998–2005, ISSN [http://www.worldcat.org/issn/0264-0414 0264-0414], doi [http://dx.doi.org/10.1080/02640414.2015.1022870 10.1080/02640414.2015.1022870]</ref>
<ref name="VernilloSavoldelli2016">Gianluca Vernillo, Aldo Savoldelli, Spyros Skafidas, Andrea Zignoli, Antonio La Torre, Barbara Pellegrini, Guido Giardini, Pietro Trabucchi, Grégoire P. Millet, Federico Schena, An Extreme Mountain Ultra-Marathon Decreases the Cost of Uphill Walking and Running, Frontiers in Physiology, volume 7, 2016, ISSN [http://www.worldcat.org/issn/1664-042X 1664-042X], doi [http://dx.doi.org/10.3389/fphys.2016.00530 10.3389/fphys.2016.00530]</ref>
<ref name=" Minetti 1994">Minetti, A. E., L. P. Ardigo, and F. Saibene. "Mechanical determinants of the minimum energy cost of gradient running in humans." Journal of Experimental Biology 195.1 (1994): 211-225.</ref>
<ref name="SnyderKram2012">K. L. Snyder, R. Kram, J. S. Gottschall, The role of elastic energy storage and recovery in downhill and uphill running, Journal of Experimental Biology, volume 215, issue 13, 2012, pages 2283–2287, ISSN [http://www.worldcat.org/issn/0022-0949 0022-0949], doi [http://dx.doi.org/10.1242/jeb.066332 10.1242/jeb.066332]</ref>
</references>
[[Category:Science]]