10 ms·

Is running a more efficient way to travel than walking?

120 points by freediver 2y ago

pverghese 2y ago
7 min mile as most efficient seems off. Not many people run a 7 min mile especially for the population of people who walk generally
- polotics 2y ago
  Lots of missing variables in the equation: how much do you carry, how much of your body weight is useful muscle versus the rest, etc... I suspect the announced most-efficient run speed is for the most efficient (light) runner.
  - AmericanChopper 2y ago
    I wouldn’t be surprised if it was quite generalizable. The lost efficiency has to be from the increased vertical travel required from running (followed by the additional stabilization required), I wouldn’t be surprised if the most efficient ratio of vertical to forward travel was very similar for a wide range of weights. I’d be more interested in how they collected the data. A skilled and fit runner will run a lot more efficiently than a less skilled and less fit runner, and you’d also expect a skilled/fit runner to run faster than a less skilled/fit runner. So depending on how they collected the data, that could be a big confounder.
- fer 2y ago
  Same opinion. There are so many wrong things with how the data is used. For starters, the data is biased because the basal metabolic rate of someone who does sports is higher than someone who doesn't, and that's without taking into account the higher metabolic rate of people who are overweight/obese (albeit for different reasons), and even for people who are fit, runners are trained to be more efficient at running (duh). But the underlying message isn't really all that insightful: the optimal running pace isn't the slowest nor the fastest, but somewhere in the middle, which is pretty obvious to anyone who's done some running.
  - Gasp0de 2y ago
    I wish 14.5km/h was my "somewhere in the middle" running speed
    - throwaway12223 2y ago
      yah they obvoiusly never ran a day in their life :P
  - Ekaros 2y ago
    Isn't same true for any mode of travel? At least terrestrial. Optimal speed is not either top or slowest speed. Lot of factors affect efficiency, but almost certainly neither very slow or maximum speed is most efficient.
    - chrisco255 2y ago
      What determines "slow" or "fast"? These are subjective quantities.
    - fer 2y ago
      It's true for most machines (as in, energy conversion). The main exception would be heating, and even then, it's usually that the optimum performance is just really close to the top performance; e.g. imperfect combustion of more fuel being less efficient than perfect combustion of less.
- newaccount74 2y ago
  7 min mile is one kilometer in 4:20. You need to be pretty fit to run that fast, especially over longer distances.
  - pastage 2y ago
    As a 17 year old I got there by running an hour three times a week, maybe I just had the body for it low weight and long legs. You will be top 25% in our local 10 km competition[1]. The track is considered perfect for running in a fast pace, people compete to get a good PB. [1] https://www.marathon.se/racetimer?v=/sv/race/resultlist/5768%3Fcheckpoint%3D9999%26amp%3Blayout%3Dmarathon%26amp%3Bpage%3D1%26amp%3Brc_id%3D22283 https://www.marathon.se/racetimer?v=/sv/race/resultlist/5768... This is two minute bins that made 10km in X minutes, only those under an hour are included. min count percentage 30 9 1 32 18 1 34 46 3 36 89 6 38 182 12 40 160 10 42 162 10 44 150 10 46 159 10 48 176 11 50 83 5 52 102 6 54 111 7 56 69 4 58 61 4 Edit: changed bin size to remove 40 minute bias.
- statguy 2y ago
  I was curious so I looked it up, it turns out that the men’s world record for a mile is 3 minutes and 43 seconds, the women’s is 4 minutes and 7 seconds. These are the very best in the world at their prime. I would conjecture that less than 50% of adults in an industrial society would be able to run a 7 min mile, which is less than twice the world record times.
  - stavros 2y ago
    > Less than 50% of adults That's a fancy way of saying "around 5%".
- serial_dev 2y ago
  I'd say it's obviously wrong? 7:00 min/miles is a 4:21 min/km, which would result in 21 min 5K, 43 min 10K, 1h 32 min half marathon and 3h 3min marathon. I can run a 7 min mile pace, but I can't sustain it for a long time, and when it comes to comparing running VS walking, 20-30 km feels like the distance you should use, as that's a distance most people could walk daily over an extended period of time (e.g a week). I was never a great long distance runner, but I took it seriously for 1.5 years and I could run a half marathon just under 2hrs. The pace the whole time felt dynamic, everything went perfect, I was significantly faster than all the joggers by the river. I needed two days to recover, and the suggested place would have been 30 minutes faster. With 7 min/mile pace, I would qualify for the Boston Marathon https://en.m.wikipedia.org/wiki/Boston_Marathon_Qualifying_Standards https://en.m.wikipedia.org/wiki/Boston_Marathon_Qualifying_S...
  - LandR 2y ago
    I'd be very happy if I could just maintain a 8min mile over 10k. 7 min mile sustained feels like an impossible goal. Hell, my best single mile is 6:48 and I'm dead at the end of that.
    - Fnoord 2y ago
      When I did a running course, I started from a bit above nothing (hence first weeks were boring) and ended at 5 km in 30 minutes (easily, with 8 min remaining). The course took 12 weeks to reach, approx 3 runs a week (so sometimes one extra day off). I was around 35 y.o. then, so it was still relatively easy to get in shape. If you're older, this is more difficult. But the course was nice because I had a (Belgian) woman in my ears telling me what to do. Really easy. You do what she tells you to. And if you can't, you still give it your best. Oh, and dear reader, do yourself a favor: do a proper warming up, every time. You don't want to retract a muscle.
    - nonameiguess 2y ago
      You're probably just getting old and I don't think most people appreciate the effect that years of being relatively sedentary can have on you. I ran competitively in high school and stayed at it mostly recreationally, but not consistently, joined the Army at one point, then got badly injured in my 30s and didn't run for nearly a decade. Now I run again in my 40s, frankly more than I ever did before. At age 12, I ran a 5:05 mile with no training except running a weekly all-out mile for PE class. At age 14, I ran a 17:14 5K after three months of training in my first cross-country meet of my first season. I PRed at 16:04 two years later. In my late 20, I was still hitting an 11:30 2-mile in the Army's fitness test pretty easily, mostly without running. I swam every day, did a lot of rowing, and ran track repeats for 8 weeks leading up to the test. Today, I run almost 80 miles a week right now, a structured, principled program, and I can't get anywhere remotely close to the times I once used to run almost effortlessly. Same person, same genetics, but in my 40s after a decade of being mostly sedentary. It takes its toll and it makes people who take this up as a hobby because they got fat in their 30s think something is impossible that likely would have been quite doable if they'd been doing it their entire lives.
- gns24 2y ago
  I don't see why that means there's anything off. Just because most of us can't produce enough energy per unit time to maintain this pace doesn't mean that it's not the most efficient pace per unit distance. Anecdotally, when I start (or re-start) running I find the pace I can run at increases quite rapidly. That makes sense with this data - although my fitness is only increasing slowly, being able to produce slightly more power actually gives a disproportionate increase in pace because the higher speed is more efficient per km.
awelxtr 2y ago
Betteridge's Law of Headlines
- bux93 2y ago
  I read an article about that one, "Betteridge's Law of Headlines: is it universally true?"
jrflowers 2y ago
TLDR: no.
donquichotte 2y ago
It's an interesting question, but only looking at energy expenditure probably does not cut it. I hike a lot and started running races in alpine territory (e.g. this one [1]) about a decade ago and think if you take into account fatigue (mental, muscle, tendons) and exposure to the elements (sun, rain, wind, snow), a light running pace can definitely make you arrive at your destination less exhausted than walking the same distance, given that you can move confidently in the given terrain. So it is a multi-dimensional optimization problem (as opposed to only optimizing for energy expenditure) and very dependent on how comfortably you can move at the given velocities. [1] https://www.youtube.com/watch?v=o-12ghcODMM https://www.youtube.com/watch?v=o-12ghcODMM
- fire_lake 2y ago
  Having done some light ultra events myself I have definitely found that going faster can be less tiring overall because you reduce overall duration - less sleep deprivation, less time on feet, etc.
  - Bomboclaat1 2y ago
    Less time on feet but under a bigger strain with less efficiency which will make you more tired. It's the same for all of these. >(sun, rain, wind, snow) You are are not as long in the sun but you are longer in the sun under a less efficient energy expenditure. You will sweat more because your are not in an ideal window. If you look at the Ultra events with 100+ Miles and tons of elevation gain, even the winners have an avg pace of a fast walking speed. There are some hikers who only hiked these events and got very good results. The more you weight the further the efficiency goes away. Even the top runners only walk the steep uphills. And in long races with lots of elevation gain at the and they are walking all hills. It's exactly because it becomes so inefficient even for lightweights
    - PaulDavisThe1st 2y ago
      > If you look at the Ultra events with 100+ Miles and tons of elevation gain, even the winners have an avg pace of a fast walking speed. There are some hikers who only hiked these events and got very good results. Sorry, but this is totally incorrect. The record for the Western States 100, which has nearly 19,000' of elevation gain, is just over 14hrs for men, and about 15.5hrs for women. Fast hiking in that terrain would be 4mph which translates to 25hrs minimum. The world's best ultra runners can maintain 6+mph average in insane terrain.
NeoTar 2y ago
To me that data looks sufficiently messy that I wouldn't feel comfortable concluding much, beyond that running is less efficient at lower speeds.
itohihiyt 2y ago
I can't say I agree with the running findings, having had to start training for a long distance run recently from not having run any sort of distance in over eight years. My physical heart cannot cope with 13km/h for anything longer than 1.5k on a treadmill. However the author has a full Wikipedia page about himself which is impressive.
- ralferoo 2y ago
  I referred to it in my other comment in this thread, but if you really want to boost your range, look into MAF (maximum aerobic fitness). The general principle is that you stay in the metabolic range where you're primarily burning fat reserves rather than using glycogen. The body typically has sufficient reserves for about 30 minutes of maximum glycogen use. The faster you run, the more glycogen you're using compared to fat, and so the quicker you'll run out and hit the wall. A lot of people don't get on with MAF because it forces you to stop running and walk a lot in the early stages (essentially, you have a target HR of 180-age and if your HR is above that, you switch to walking), and even when your body does adapt and you can keep running all the time, you have to run much, much slower than you think you're capable of and that you probably want to be running at. But, over time you'll find your body gets more efficient and your speed at the target HR goes up over time. But to translate it into normal terminologoy, it's like you're always training in zone 2, although for most people 180-age is lower than the calculated top of zone 2. An anecdotal result is that I used to be exhausted at the end of a 5km because I was running as fast as I could. Within a few weeks of switching to MAF training, I was routinely doing 10km-15km without really feeling tired and within a month I'd accidentally done a half marathon (very slowly, of course) after getting lost and being stuck on the wrong side of the river for 4km longer than I planned, and then an extra 3km the other side. I was tired at the end of that, but I also never would have believed I was even capable of that distance a month earlier.
Zacharias030 2y ago
This problem was treated with a bit more sophistication by Harvards Lieberman in „A story of the human body“ and the corresponding nature article [0] establishing persistence hunting as an ancestoral hunting technique of homo sapien. See figure 2b for the plot you were looking for. Running faster is less efficient but only slightly so and walking is a U-shaped curve like most mammal gaites. It shows that in contrast to most animals, the efficiency curve of humans for running speeds is extremely flat, ie, we are about equally efficient at many different speeds, while the kind of game that we hunted was not. The discrepancy allowed us to find a speed where we could exhaust the animal after 10-30km (as I understand) provided we were also excellent trackers. https://www.nature.com/articles/nature03052.epdf?sharing_token=Ke6yvZKEVvMSKfUfm73bRdRgN0jAjWel9jnR3ZoTv0O52bUtxu-KLGqf6fqgad3OSqMqJaMeK92lj8PCB6XF1Qyn_5NI3MevfRHMNt3k02KmOyi4lzTf25oCQ2IVJCCPw6fi1slyYdmvI2Lq7aWg7XbWSbkOR64ywDxfVHwBO-jtvtUW18XS_S2tNVsHXnu7cio0yNj9BUxvU_9644LdsuKX7HUlTbxe0_kJLVwf-K8WuGIXOhYcsBqwthDp2ZSN44xVeT4kKegfb_sXC6qD_Q%3D%3D&tracking_referrer=www.nature.com https://www.nature.com/articles/nature03052.epdf?sharing_tok...
- Mistletoe 2y ago
  I'm a runner and have had a weird question, could a runner defeat a larger human in this way? Like if I found myself in mortal combat with The Rock at 260 lbs after his steroids cycle, could I just repeatedly run away and follow him (while staying out of range) until he tired out and then bonk him on the head with a rock, like a tired antelope? (No offense to The Rock, seems like a great guy) Might explain why we aren't all musclebound and huge? Although I'm sure food availability had more influence.
  - underlipton 2y ago
    Layman: skeletal muscles are expensive to maintain in terms of caloric and protein/water intake, and larger muscles are less efficient at dumping the heat that their use generates because volume increases faster than exposed surface area with muscular hypertrophy. If food and body temperature regulation were more immediate concerns than violent conflict, then the ability to gas out your opponent was probably less influential.
  - 2y ago
culebron21 2y ago
7 min/mile, or 100 m in 25 seconds seems doable if you excercise regularly, but not for an average human. Higher speeds mean higher power (watts or cal/sec), to which there are limits.
- LandR 2y ago
  Depends on how many miles you are doing. If you only want to do 1 mile at 7 min, then that is doable, if you want to do 10k at that pace... I reckon you'd have to be a VERY fit and strong runner.
- jdubner 2y ago
  > 7 min/mile, or 100 m in 25 seconds seems doable if you excercise regularly ... I have to disagree. I run 20 miles per week at about 11 min/mile yet could not run a single 7-minute mile to save my life. The best I can do at a "max effort" is a single 9-minute mile. Never even a 100-yard stretch in the 8s. But then, I'm 77 years old. Nowhere in this discussion have I seen an accounting for age. Perhaps with advancing age walking is more efficient (whatever the metric) regardless. Anecdotally (I see that word used here a lot <g>) I don't see any other runners my age, only walkers, so that must be true.
FabHK 2y ago
Calories are not metric. Joules are. 1 MET = 4184 J/(kg hr), and, since a joule is a kg m/s^2, 1 MET = 1.162 m^2/s^3
- Mordisquitos 2y ago
  >Calories are not metric. Joules are. To make that unit even more confusing, by convention a Calorie is equal to a kilocalorie or 1000 calories.
ralferoo 2y ago
The article seems to actually be answering a different question than it poses. From my experience of roughly analysing this a couple of years ago when I was losing quite a lot of weight, I drew two main conclusions: * Calories used is a function of total distance travelled and your weight, your speed isn't really that significant a factor. * Walking rather than running uses about 80% of the calories for the same distance compared to running. It seems to be based on the mechanics of changing gait. If you at walking speed (google MAF - maximum aerobic fitness for more info), you use more calories than just walking. While these would seem to be opposite to the conclusions in the article, it's worth noting that the MET value is a function of calories over time, not calories over distance. The faster you're moving, the more calories you're using and the greater the distance you're covering, and they roughly cancel out. I also found it interesting that running slowly and/or walking is better for losing weight as running faster primarily uses glycogen (and makes you hungry), and running slowly primarily uses fat. This doesn't really affect energy efficiency, per se, but fat is a more efficient energy storage source, so this might be relevant in answering the posed question. But in any case, if you want to lose weight, walking is significantly more useful than running as you can generally sustain the activity over a longer period of time, and with less stress on your body.
- rob74 2y ago
  Well, the answer to the initial question is kind of obvious I think: running is less efficient (for the same speed) because when running more of your energy goes into vertical motion (jumping from one foot to the other) than into horizontal motion. Of course, above certain speeds walking just isn't "feasible" anymore, but running will never be as efficient as walking at the optimal speeds for walking. ...but if you want the most efficient way to travel only with the power of your own muscles, you need a bicycle :)
- david-gpu 2y ago
  Purely anecdotal, but I was surprised to find out that I gained significant weight when I switched from walking 6 hours/week to riding a bike for the same amount of time. I find it much harder to recover from riding, which makes sense because my heart rate goes way higher. Riding is much more fun, but I suspect you are completely right about walking being the better choice for weight loss. I was at my leanest when my breakfast was just black coffee and it was followed by a 60-90 minute walk.
rcastellotti 2y ago
what a fantastic example of https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headlines https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headline...
TrackerFF 2y ago
Hmm a 7 min mile is equivalent to 13.79 km/h. That gives you a hair over 13 min time on a 3000m run. When I was in the (Norwegian) military, that time would get you a 7 out of 9 score for males, and 8 (or 9) out of 9 score for females on a physical test. Pretty solid score. It would also almost give you a sub 3 hour marathon. You'd be a pretty capable runner if you can keep a steady 7 min mile, for the sake of running efficiently!
- kijin 2y ago
  Another commenter talked about prehistoric hunters chasing game. I would assume that those hunters were quite a bit more fit than the average Western dude today. It's also not surprising that a human body in good shape is still optimized for that prehistoric lifestyle.
  - davzie 2y ago
    I think they benefited from slower runs across the course of days rather than sprints to chase game. Lots of animals are faster than humans, but in order to cool down they have to stop. From what I've read, humans' ability to run and stay cool through sweating allowed them to, over the course of days track and just simply wear out animals to the point the animal would just collapse from exhaustion.
- fire_lake 2y ago
  That is an impressive marathon time but over 3km it’s not very fast at all! I expected military standards to be more stringent?
  - TrackerFF 2y ago
    A 7 min mile would pass most special forces (selection) requirements around the world. For BUD/S (Navy Seals), it seems like a 1.5 mile run is part of the physical screening test, a 10m30s time would put you 10 seconds from the "competitive category". Minimum requirement is 11m And from my memory, that was roughly the same requirements in my country for most SOF positions. But, of course, those screening tests aren't necessarily done under ideal conditions. But if you can do a 7 min mile, it's not your conditioning that will stop you. You should be able to pass the minimum requirements for every position in the military.
oldpersonintx 2y ago
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T4iga 2y ago
The difference between an untrained runner, a trained runner and n elite athlete are left completely unanalyzed. Given how seemingly varied for no apparent reason some of these points on the graph are and coming from an anecdotal perspective this analysis is not very useful, and probably even wrong. Seemingly an elite athlete must have been tracked because almost nobody(considering the whole population) can run the given top-end pace for a sustained amount of time (More that 100metres). I was hoping for more from the article, or at least that it was called 'calorically More efficient'.
- wiether 2y ago
  It's not like the author says this: > The answer probably depends on the person. Someone who regularly runs, runs more efficiently than someone who does not. > But we can still generalize.
derriz 2y ago
Requires a correction: "about 9 mph or a pace of 6.6 miles per minute" should be "about 9 mph or a pace of 6.6 minutes per mile"
a3w 2y ago
Who does science in imperial units?! Thats what crashes stuff and people into hard objects. Well, then again, they use kcal, instead of Joule. Which has conflicting definitions by a small percentage. And usually, the kilo-part is hidden. Making some calcuations off by a factor of one thousand.
jowdones 2y ago
I can walk for hours but can't run more than a few minutes. So obvious conclusion. If the goal is "traveling" then running doesn't even qualify. Soldiers marching 20 miles a day don't run'em. They walk.
- askvictor 2y ago
  Yeah this. I can't imagine running a marathon. But walk 40km straight? I'd be tired, but could definitely do it.
drtgh 2y ago
Efficient or not (the conclusion may be premature due oversimplified numbers, IMHO), the repetitive impact of running will wear down the cartilage and meniscus, essentially causing premature ageing of the knees when used routinely; this variable should be considered as a deferred efficiency cost also. It doesn't seem that our body sees running as a method of travel, given our inability to regenerate cartilage and due the dehydration through cooling, it sounds more like a momentarily needed resource for survival.
- echelon_musk 2y ago
  > the repetitive impact of running will wear down the cartilage and meniscus, essentially causing premature ageing of the knees when used routinely This concerned me as someone who benefits from running. I found the following study which says "Cumulative number of years running, number of marathons completed, weekly mileage, and mean running pace were not significant predictors for arthritis". https://pubmed.ncbi.nlm.nih.gov/37555313/ https://pubmed.ncbi.nlm.nih.gov/37555313/
  - carlmr 2y ago
    I found running style is a major contributor. I got knee pain preparing for a 10K run in my early 20s. When I stopped for a month it would go aways, but when I started again it would instantly come back. I then learned about natural running (forefoot strike, using your joints for suspensions) which made logical sense to me. I could run again, even every day, and even more than a decade later no knee pain when running. It does have the added benefit that you don't even need expensive running shoes anymore, because you use your body's joints for suspension instead of some gel midsole. There is a slightly higher risk of ankle injury, which did happen once in over a decade. But otherwise I think natural running just makes so much sense. You should also ease into it, because you need to train your calf muscles to do a bit more work.
    - echelon_musk 2y ago
      Thank you for providing this information. I've been getting hip pain when running so I'll see if I can incorporate and test the effects of a forefoot strike.
wslh 2y ago
A little bit stretch but as someone who decide to run "slowly" in long distances, the other metric is sweating. If it not were by sweating I prefer to run at a controlled pace than to walk.
WalterBright 2y ago
I suppose a lot could depend on form. Most people run in a manner where they push them selves up and slap back down. If you run so that from the hips up you stay at the same altitude, I expect it would use much less energy.
Fnoord 2y ago
Need to take into account different body types, and whether the goal is to burn calories or not. Whether there is time gained or not. Say, walking is evidently more efficient than running. Why do people run then? Because circumstances demand it; because they like to stay or get into shape, because they want to burn fat, because they enjoy a change of pace, or because they need to catch a bus. Or simply: because they can / find it fun (children). Speaking of children: hopping is the most efficient form of movement for small children (IIRC around the age of 6).
justinator 2y ago
a 7 minute mile is the most efficient That works out to a 3:03 marathon time. That's years of work to become so efficient. I'm a little bummed that the article doesn't touch on how can maintain that pace for x amount of miles, since plainly: only people who have trained very carefully have a chance. So that running speed is off the table. Stick to walking.
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mettamage 2y ago
I find it a lot more fun. Are the psychological benefits taken into account? My attention is always better after running.
gumby 2y ago
As far as human endurance goes (more the topic of various comments than the article), humans can outrun a horse, most recently last year: https://www.bbc.com/news/uk-wales-65867327 https://www.bbc.com/news/uk-wales-65867327 I seem to remember reading as a kid that this happened first in some Victorian bet (I would have read this in one of my dad’s kid’s books from the 1930s). This was also a plot device in a Larry Niven short story (one of the Draco’s Tavern stories).
meroes 2y ago
I think calorie-wise running/jogging is roughly half the time to cover a distance for twice the calories per second compared to moderate walking. You could slice this a million ways to tease out many different efficiencies.
rtchau 2y ago
No, I don't believe that it would be. In terms of "calories expended over distance", it'd be pretty close, but we're made for endurance, not raw speed. From what I understand, the energy budget of the human body is tuned for 2 things: neurological activity (the energy consumption of which far exceeds any other animal on earth) and endurance. It's what makes us such terrifying hunters... prey can outrun us but then when they invariably have to stop to recover, we eventually just turn up and they have to keep running again. So, any activity where you're cranking the ol' powerhouse up to 120% and going for a run is going to incur a cost, both in terms of energy consumption (which, as the post demonstrates, is slightly more efficient than a fast-paced walk), but then also the resultant metabolic waste which needs to be eliminated, which is a process that takes place during recovery in the 24hrs or so after you've completed your "efficient" 7-minute mile, and I don't believe the article takes this into account. I watched an interesting video recently (I think it was Kurzgesagt?) that talks about the illusion of high-intensity activity vs low-intensity but longer-duration activity.
- NoPicklez 2y ago
  We aren't talking about sprinting or 120% type running in this debate. We used to catch our prey through running, but not at breakneck speeds. Humans are absolutely made for endurance running, but not at 120% speeds.
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nayuki 2y ago
> 1 MET is 1 kcal/kg/hr These guys need to get with the program and use metric units. For example, the cycling world uses watts per kilogram (W/kg) to quantify an athlete's output. This is the correct unit to use. To help with this, note that 1 MET ≈ 1.162 W/kg.
- scotty79 2y ago
  Calorie is a part of International System of Units (SI). But I agree it's lame.
  - nayuki 2y ago
    The calorie is not part of the current SI. The SI unit that measures the same quantity is the joule (J). Like all SI derived units, the joule is obtained by multiplying or dividing any number of SI base units, without using numeric scaling factors. 1 joule = 1 newton × 1 kilogram = m^2 × kg × s^−2. The calorie measures the same quantity as the joule (energy or work), but 1 calorie = 4.184 joules. SI generally disallows having multiple units that measure the same quantity (e.g. tesla vs. gauss), especially ones that have numerical scaling factors (e.g. 1 bar = 100 kilopascals). Quotes and references: > the kcal is not officially part of the International System of Units (SI), and is regarded as obsolete, having been replaced in many uses by the SI derived unit of energy, the joule (J) -- https://en.wikipedia.org/wiki/Calorie https://en.wikipedia.org/wiki/Calorie > (this page does not contain any mention of the word "calorie") -- https://en.wikipedia.org/wiki/International_System_of_Units https://en.wikipedia.org/wiki/International_System_of_Units > (Section 4: Units outside the SI) (page 29) Examples of other non-SI units: calorie > (page 52) (year 1948) calorie > (Section 2.2: SI derived units) (page 21) SI derived units with special names and symbols: joule | J | N ⋅ m | m^2 ⋅ kg ⋅ s^−2 -- https://physics.nist.gov/cuu/pdf/sp330.pdf https://physics.nist.gov/cuu/pdf/sp330.pdf
two_handfuls 2y ago
A nitpick: the author states that `kcal/kg/h = kcal/kgh`. This is false, because multiply and divide have the same priority and so are applied left to right. The correct way to write this is: `kcal/kg/h = kcal/(kgh)` The actual computations in the article are unaffected.

120 points by freediver 2y ago

7 min mile as most efficient seems off. Not many people run a 7 min mile especially for the population of people who walk generally

polotics 2y ago
Lots of missing variables in the equation: how much do you carry, how much of your body weight is useful muscle versus the rest, etc... I suspect the announced most-efficient run speed is for the most efficient (light) runner.
- AmericanChopper 2y ago
  I wouldn’t be surprised if it was quite generalizable. The lost efficiency has to be from the increased vertical travel required from running (followed by the additional stabilization required), I wouldn’t be surprised if the most efficient ratio of vertical to forward travel was very similar for a wide range of weights. I’d be more interested in how they collected the data. A skilled and fit runner will run a lot more efficiently than a less skilled and less fit runner, and you’d also expect a skilled/fit runner to run faster than a less skilled/fit runner. So depending on how they collected the data, that could be a big confounder.
fer 2y ago
Same opinion. There are so many wrong things with how the data is used. For starters, the data is biased because the basal metabolic rate of someone who does sports is higher than someone who doesn't, and that's without taking into account the higher metabolic rate of people who are overweight/obese (albeit for different reasons), and even for people who are fit, runners are trained to be more efficient at running (duh). But the underlying message isn't really all that insightful: the optimal running pace isn't the slowest nor the fastest, but somewhere in the middle, which is pretty obvious to anyone who's done some running.
- Gasp0de 2y ago
  I wish 14.5km/h was my "somewhere in the middle" running speed
  - throwaway12223 2y ago
    yah they obvoiusly never ran a day in their life :P
- Ekaros 2y ago
  Isn't same true for any mode of travel? At least terrestrial. Optimal speed is not either top or slowest speed. Lot of factors affect efficiency, but almost certainly neither very slow or maximum speed is most efficient.
  - chrisco255 2y ago
    What determines "slow" or "fast"? These are subjective quantities.
  - fer 2y ago
    It's true for most machines (as in, energy conversion). The main exception would be heating, and even then, it's usually that the optimum performance is just really close to the top performance; e.g. imperfect combustion of more fuel being less efficient than perfect combustion of less.
newaccount74 2y ago
7 min mile is one kilometer in 4:20. You need to be pretty fit to run that fast, especially over longer distances.
- pastage 2y ago
  As a 17 year old I got there by running an hour three times a week, maybe I just had the body for it low weight and long legs. You will be top 25% in our local 10 km competition[1]. The track is considered perfect for running in a fast pace, people compete to get a good PB. [1] https://www.marathon.se/racetimer?v=/sv/race/resultlist/5768%3Fcheckpoint%3D9999%26amp%3Blayout%3Dmarathon%26amp%3Bpage%3D1%26amp%3Brc_id%3D22283 https://www.marathon.se/racetimer?v=/sv/race/resultlist/5768... This is two minute bins that made 10km in X minutes, only those under an hour are included. min count percentage 30 9 1 32 18 1 34 46 3 36 89 6 38 182 12 40 160 10 42 162 10 44 150 10 46 159 10 48 176 11 50 83 5 52 102 6 54 111 7 56 69 4 58 61 4 Edit: changed bin size to remove 40 minute bias.
statguy 2y ago
I was curious so I looked it up, it turns out that the men’s world record for a mile is 3 minutes and 43 seconds, the women’s is 4 minutes and 7 seconds. These are the very best in the world at their prime. I would conjecture that less than 50% of adults in an industrial society would be able to run a 7 min mile, which is less than twice the world record times.
- stavros 2y ago
  > Less than 50% of adults That's a fancy way of saying "around 5%".
serial_dev 2y ago
I'd say it's obviously wrong? 7:00 min/miles is a 4:21 min/km, which would result in 21 min 5K, 43 min 10K, 1h 32 min half marathon and 3h 3min marathon. I can run a 7 min mile pace, but I can't sustain it for a long time, and when it comes to comparing running VS walking, 20-30 km feels like the distance you should use, as that's a distance most people could walk daily over an extended period of time (e.g a week). I was never a great long distance runner, but I took it seriously for 1.5 years and I could run a half marathon just under 2hrs. The pace the whole time felt dynamic, everything went perfect, I was significantly faster than all the joggers by the river. I needed two days to recover, and the suggested place would have been 30 minutes faster. With 7 min/mile pace, I would qualify for the Boston Marathon https://en.m.wikipedia.org/wiki/Boston_Marathon_Qualifying_Standards https://en.m.wikipedia.org/wiki/Boston_Marathon_Qualifying_S...
- LandR 2y ago
  I'd be very happy if I could just maintain a 8min mile over 10k. 7 min mile sustained feels like an impossible goal. Hell, my best single mile is 6:48 and I'm dead at the end of that.
  - Fnoord 2y ago
    When I did a running course, I started from a bit above nothing (hence first weeks were boring) and ended at 5 km in 30 minutes (easily, with 8 min remaining). The course took 12 weeks to reach, approx 3 runs a week (so sometimes one extra day off). I was around 35 y.o. then, so it was still relatively easy to get in shape. If you're older, this is more difficult. But the course was nice because I had a (Belgian) woman in my ears telling me what to do. Really easy. You do what she tells you to. And if you can't, you still give it your best. Oh, and dear reader, do yourself a favor: do a proper warming up, every time. You don't want to retract a muscle.
  - nonameiguess 2y ago
    You're probably just getting old and I don't think most people appreciate the effect that years of being relatively sedentary can have on you. I ran competitively in high school and stayed at it mostly recreationally, but not consistently, joined the Army at one point, then got badly injured in my 30s and didn't run for nearly a decade. Now I run again in my 40s, frankly more than I ever did before. At age 12, I ran a 5:05 mile with no training except running a weekly all-out mile for PE class. At age 14, I ran a 17:14 5K after three months of training in my first cross-country meet of my first season. I PRed at 16:04 two years later. In my late 20, I was still hitting an 11:30 2-mile in the Army's fitness test pretty easily, mostly without running. I swam every day, did a lot of rowing, and ran track repeats for 8 weeks leading up to the test. Today, I run almost 80 miles a week right now, a structured, principled program, and I can't get anywhere remotely close to the times I once used to run almost effortlessly. Same person, same genetics, but in my 40s after a decade of being mostly sedentary. It takes its toll and it makes people who take this up as a hobby because they got fat in their 30s think something is impossible that likely would have been quite doable if they'd been doing it their entire lives.
gns24 2y ago
I don't see why that means there's anything off. Just because most of us can't produce enough energy per unit time to maintain this pace doesn't mean that it's not the most efficient pace per unit distance. Anecdotally, when I start (or re-start) running I find the pace I can run at increases quite rapidly. That makes sense with this data - although my fitness is only increasing slowly, being able to produce slightly more power actually gives a disproportionate increase in pace because the higher speed is more efficient per km.

awelxtr 2y ago

Betteridge's Law of Headlines

bux93 2y ago
I read an article about that one, "Betteridge's Law of Headlines: is it universally true?"

jrflowers 2y ago

TLDR: no.

donquichotte 2y ago

It's an interesting question, but only looking at energy expenditure probably does not cut it. I hike a lot and started running races in alpine territory (e.g. this one [1]) about a decade ago and think if you take into account fatigue (mental, muscle, tendons) and exposure to the elements (sun, rain, wind, snow), a light running pace can definitely make you arrive at your destination less exhausted than walking the same distance, given that you can move confidently in the given terrain. So it is a multi-dimensional optimization problem (as opposed to only optimizing for energy expenditure) and very dependent on how comfortably you can move at the given velocities. [1] https://www.youtube.com/watch?v=o-12ghcODMM https://www.youtube.com/watch?v=o-12ghcODMM

fire_lake 2y ago
Having done some light ultra events myself I have definitely found that going faster can be less tiring overall because you reduce overall duration - less sleep deprivation, less time on feet, etc.
- Bomboclaat1 2y ago
  Less time on feet but under a bigger strain with less efficiency which will make you more tired. It's the same for all of these. >(sun, rain, wind, snow) You are are not as long in the sun but you are longer in the sun under a less efficient energy expenditure. You will sweat more because your are not in an ideal window. If you look at the Ultra events with 100+ Miles and tons of elevation gain, even the winners have an avg pace of a fast walking speed. There are some hikers who only hiked these events and got very good results. The more you weight the further the efficiency goes away. Even the top runners only walk the steep uphills. And in long races with lots of elevation gain at the and they are walking all hills. It's exactly because it becomes so inefficient even for lightweights
  - PaulDavisThe1st 2y ago
    > If you look at the Ultra events with 100+ Miles and tons of elevation gain, even the winners have an avg pace of a fast walking speed. There are some hikers who only hiked these events and got very good results. Sorry, but this is totally incorrect. The record for the Western States 100, which has nearly 19,000' of elevation gain, is just over 14hrs for men, and about 15.5hrs for women. Fast hiking in that terrain would be 4mph which translates to 25hrs minimum. The world's best ultra runners can maintain 6+mph average in insane terrain.

NeoTar 2y ago

To me that data looks sufficiently messy that I wouldn't feel comfortable concluding much, beyond that running is less efficient at lower speeds.

itohihiyt 2y ago

I can't say I agree with the running findings, having had to start training for a long distance run recently from not having run any sort of distance in over eight years. My physical heart cannot cope with 13km/h for anything longer than 1.5k on a treadmill. However the author has a full Wikipedia page about himself which is impressive.

ralferoo 2y ago
I referred to it in my other comment in this thread, but if you really want to boost your range, look into MAF (maximum aerobic fitness). The general principle is that you stay in the metabolic range where you're primarily burning fat reserves rather than using glycogen. The body typically has sufficient reserves for about 30 minutes of maximum glycogen use. The faster you run, the more glycogen you're using compared to fat, and so the quicker you'll run out and hit the wall. A lot of people don't get on with MAF because it forces you to stop running and walk a lot in the early stages (essentially, you have a target HR of 180-age and if your HR is above that, you switch to walking), and even when your body does adapt and you can keep running all the time, you have to run much, much slower than you think you're capable of and that you probably want to be running at. But, over time you'll find your body gets more efficient and your speed at the target HR goes up over time. But to translate it into normal terminologoy, it's like you're always training in zone 2, although for most people 180-age is lower than the calculated top of zone 2. An anecdotal result is that I used to be exhausted at the end of a 5km because I was running as fast as I could. Within a few weeks of switching to MAF training, I was routinely doing 10km-15km without really feeling tired and within a month I'd accidentally done a half marathon (very slowly, of course) after getting lost and being stuck on the wrong side of the river for 4km longer than I planned, and then an extra 3km the other side. I was tired at the end of that, but I also never would have believed I was even capable of that distance a month earlier.

Zacharias030 2y ago

This problem was treated with a bit more sophistication by Harvards Lieberman in „A story of the human body“ and the corresponding nature article [0] establishing persistence hunting as an ancestoral hunting technique of homo sapien. See figure 2b for the plot you were looking for. Running faster is less efficient but only slightly so and walking is a U-shaped curve like most mammal gaites. It shows that in contrast to most animals, the efficiency curve of humans for running speeds is extremely flat, ie, we are about equally efficient at many different speeds, while the kind of game that we hunted was not. The discrepancy allowed us to find a speed where we could exhaust the animal after 10-30km (as I understand) provided we were also excellent trackers. https://www.nature.com/articles/nature03052.epdf?sharing_token=Ke6yvZKEVvMSKfUfm73bRdRgN0jAjWel9jnR3ZoTv0O52bUtxu-KLGqf6fqgad3OSqMqJaMeK92lj8PCB6XF1Qyn_5NI3MevfRHMNt3k02KmOyi4lzTf25oCQ2IVJCCPw6fi1slyYdmvI2Lq7aWg7XbWSbkOR64ywDxfVHwBO-jtvtUW18XS_S2tNVsHXnu7cio0yNj9BUxvU_9644LdsuKX7HUlTbxe0_kJLVwf-K8WuGIXOhYcsBqwthDp2ZSN44xVeT4kKegfb_sXC6qD_Q%3D%3D&tracking_referrer=www.nature.com https://www.nature.com/articles/nature03052.epdf?sharing_tok...

Mistletoe 2y ago
I'm a runner and have had a weird question, could a runner defeat a larger human in this way? Like if I found myself in mortal combat with The Rock at 260 lbs after his steroids cycle, could I just repeatedly run away and follow him (while staying out of range) until he tired out and then bonk him on the head with a rock, like a tired antelope? (No offense to The Rock, seems like a great guy) Might explain why we aren't all musclebound and huge? Although I'm sure food availability had more influence.
- underlipton 2y ago
  Layman: skeletal muscles are expensive to maintain in terms of caloric and protein/water intake, and larger muscles are less efficient at dumping the heat that their use generates because volume increases faster than exposed surface area with muscular hypertrophy. If food and body temperature regulation were more immediate concerns than violent conflict, then the ability to gas out your opponent was probably less influential.
- 2y ago

culebron21 2y ago

7 min/mile, or 100 m in 25 seconds seems doable if you excercise regularly, but not for an average human. Higher speeds mean higher power (watts or cal/sec), to which there are limits.

LandR 2y ago
Depends on how many miles you are doing. If you only want to do 1 mile at 7 min, then that is doable, if you want to do 10k at that pace... I reckon you'd have to be a VERY fit and strong runner.
jdubner 2y ago
> 7 min/mile, or 100 m in 25 seconds seems doable if you excercise regularly ... I have to disagree. I run 20 miles per week at about 11 min/mile yet could not run a single 7-minute mile to save my life. The best I can do at a "max effort" is a single 9-minute mile. Never even a 100-yard stretch in the 8s. But then, I'm 77 years old. Nowhere in this discussion have I seen an accounting for age. Perhaps with advancing age walking is more efficient (whatever the metric) regardless. Anecdotally (I see that word used here a lot <g>) I don't see any other runners my age, only walkers, so that must be true.

FabHK 2y ago

Calories are not metric. Joules are. 1 MET = 4184 J/(kg hr), and, since a joule is a kg m/s^2, 1 MET = 1.162 m^2/s^3

Mordisquitos 2y ago
>Calories are not metric. Joules are. To make that unit even more confusing, by convention a Calorie is equal to a kilocalorie or 1000 calories.

ralferoo 2y ago

The article seems to actually be answering a different question than it poses. From my experience of roughly analysing this a couple of years ago when I was losing quite a lot of weight, I drew two main conclusions: * Calories used is a function of total distance travelled and your weight, your speed isn't really that significant a factor. * Walking rather than running uses about 80% of the calories for the same distance compared to running. It seems to be based on the mechanics of changing gait. If you at walking speed (google MAF - maximum aerobic fitness for more info), you use more calories than just walking. While these would seem to be opposite to the conclusions in the article, it's worth noting that the MET value is a function of calories over time, not calories over distance. The faster you're moving, the more calories you're using and the greater the distance you're covering, and they roughly cancel out. I also found it interesting that running slowly and/or walking is better for losing weight as running faster primarily uses glycogen (and makes you hungry), and running slowly primarily uses fat. This doesn't really affect energy efficiency, per se, but fat is a more efficient energy storage source, so this might be relevant in answering the posed question. But in any case, if you want to lose weight, walking is significantly more useful than running as you can generally sustain the activity over a longer period of time, and with less stress on your body.

rob74 2y ago
Well, the answer to the initial question is kind of obvious I think: running is less efficient (for the same speed) because when running more of your energy goes into vertical motion (jumping from one foot to the other) than into horizontal motion. Of course, above certain speeds walking just isn't "feasible" anymore, but running will never be as efficient as walking at the optimal speeds for walking. ...but if you want the most efficient way to travel only with the power of your own muscles, you need a bicycle :)
david-gpu 2y ago
Purely anecdotal, but I was surprised to find out that I gained significant weight when I switched from walking 6 hours/week to riding a bike for the same amount of time. I find it much harder to recover from riding, which makes sense because my heart rate goes way higher. Riding is much more fun, but I suspect you are completely right about walking being the better choice for weight loss. I was at my leanest when my breakfast was just black coffee and it was followed by a 60-90 minute walk.

rcastellotti 2y ago

what a fantastic example of https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headlines https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headline...

TrackerFF 2y ago

Hmm a 7 min mile is equivalent to 13.79 km/h. That gives you a hair over 13 min time on a 3000m run. When I was in the (Norwegian) military, that time would get you a 7 out of 9 score for males, and 8 (or 9) out of 9 score for females on a physical test. Pretty solid score. It would also almost give you a sub 3 hour marathon. You'd be a pretty capable runner if you can keep a steady 7 min mile, for the sake of running efficiently!

kijin 2y ago
Another commenter talked about prehistoric hunters chasing game. I would assume that those hunters were quite a bit more fit than the average Western dude today. It's also not surprising that a human body in good shape is still optimized for that prehistoric lifestyle.
- davzie 2y ago
  I think they benefited from slower runs across the course of days rather than sprints to chase game. Lots of animals are faster than humans, but in order to cool down they have to stop. From what I've read, humans' ability to run and stay cool through sweating allowed them to, over the course of days track and just simply wear out animals to the point the animal would just collapse from exhaustion.
fire_lake 2y ago
That is an impressive marathon time but over 3km it’s not very fast at all! I expected military standards to be more stringent?
- TrackerFF 2y ago
  A 7 min mile would pass most special forces (selection) requirements around the world. For BUD/S (Navy Seals), it seems like a 1.5 mile run is part of the physical screening test, a 10m30s time would put you 10 seconds from the "competitive category". Minimum requirement is 11m And from my memory, that was roughly the same requirements in my country for most SOF positions. But, of course, those screening tests aren't necessarily done under ideal conditions. But if you can do a 7 min mile, it's not your conditioning that will stop you. You should be able to pass the minimum requirements for every position in the military.

oldpersonintx 2y ago

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T4iga 2y ago

The difference between an untrained runner, a trained runner and n elite athlete are left completely unanalyzed. Given how seemingly varied for no apparent reason some of these points on the graph are and coming from an anecdotal perspective this analysis is not very useful, and probably even wrong. Seemingly an elite athlete must have been tracked because almost nobody(considering the whole population) can run the given top-end pace for a sustained amount of time (More that 100metres). I was hoping for more from the article, or at least that it was called 'calorically More efficient'.

wiether 2y ago
It's not like the author says this: > The answer probably depends on the person. Someone who regularly runs, runs more efficiently than someone who does not. > But we can still generalize.

derriz 2y ago

Requires a correction: "about 9 mph or a pace of 6.6 miles per minute" should be "about 9 mph or a pace of 6.6 minutes per mile"

a3w 2y ago

Who does science in imperial units?! Thats what crashes stuff and people into hard objects. Well, then again, they use kcal, instead of Joule. Which has conflicting definitions by a small percentage. And usually, the kilo-part is hidden. Making some calcuations off by a factor of one thousand.

jowdones 2y ago

I can walk for hours but can't run more than a few minutes. So obvious conclusion. If the goal is "traveling" then running doesn't even qualify. Soldiers marching 20 miles a day don't run'em. They walk.

askvictor 2y ago
Yeah this. I can't imagine running a marathon. But walk 40km straight? I'd be tired, but could definitely do it.

drtgh 2y ago

Efficient or not (the conclusion may be premature due oversimplified numbers, IMHO), the repetitive impact of running will wear down the cartilage and meniscus, essentially causing premature ageing of the knees when used routinely; this variable should be considered as a deferred efficiency cost also. It doesn't seem that our body sees running as a method of travel, given our inability to regenerate cartilage and due the dehydration through cooling, it sounds more like a momentarily needed resource for survival.

echelon_musk 2y ago
> the repetitive impact of running will wear down the cartilage and meniscus, essentially causing premature ageing of the knees when used routinely This concerned me as someone who benefits from running. I found the following study which says "Cumulative number of years running, number of marathons completed, weekly mileage, and mean running pace were not significant predictors for arthritis". https://pubmed.ncbi.nlm.nih.gov/37555313/ https://pubmed.ncbi.nlm.nih.gov/37555313/
- carlmr 2y ago
  I found running style is a major contributor. I got knee pain preparing for a 10K run in my early 20s. When I stopped for a month it would go aways, but when I started again it would instantly come back. I then learned about natural running (forefoot strike, using your joints for suspensions) which made logical sense to me. I could run again, even every day, and even more than a decade later no knee pain when running. It does have the added benefit that you don't even need expensive running shoes anymore, because you use your body's joints for suspension instead of some gel midsole. There is a slightly higher risk of ankle injury, which did happen once in over a decade. But otherwise I think natural running just makes so much sense. You should also ease into it, because you need to train your calf muscles to do a bit more work.
  - echelon_musk 2y ago
    Thank you for providing this information. I've been getting hip pain when running so I'll see if I can incorporate and test the effects of a forefoot strike.

wslh 2y ago

A little bit stretch but as someone who decide to run "slowly" in long distances, the other metric is sweating. If it not were by sweating I prefer to run at a controlled pace than to walk.

WalterBright 2y ago

I suppose a lot could depend on form. Most people run in a manner where they push them selves up and slap back down. If you run so that from the hips up you stay at the same altitude, I expect it would use much less energy.

Fnoord 2y ago

Need to take into account different body types, and whether the goal is to burn calories or not. Whether there is time gained or not. Say, walking is evidently more efficient than running. Why do people run then? Because circumstances demand it; because they like to stay or get into shape, because they want to burn fat, because they enjoy a change of pace, or because they need to catch a bus. Or simply: because they can / find it fun (children). Speaking of children: hopping is the most efficient form of movement for small children (IIRC around the age of 6).

justinator 2y ago

a 7 minute mile is the most efficient That works out to a 3:03 marathon time. That's years of work to become so efficient. I'm a little bummed that the article doesn't touch on how can maintain that pace for x amount of miles, since plainly: only people who have trained very carefully have a chance. So that running speed is off the table. Stick to walking.

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mettamage 2y ago

I find it a lot more fun. Are the psychological benefits taken into account? My attention is always better after running.

gumby 2y ago

As far as human endurance goes (more the topic of various comments than the article), humans can outrun a horse, most recently last year: https://www.bbc.com/news/uk-wales-65867327 https://www.bbc.com/news/uk-wales-65867327 I seem to remember reading as a kid that this happened first in some Victorian bet (I would have read this in one of my dad’s kid’s books from the 1930s). This was also a plot device in a Larry Niven short story (one of the Draco’s Tavern stories).

meroes 2y ago

I think calorie-wise running/jogging is roughly half the time to cover a distance for twice the calories per second compared to moderate walking. You could slice this a million ways to tease out many different efficiencies.

rtchau 2y ago

No, I don't believe that it would be. In terms of "calories expended over distance", it'd be pretty close, but we're made for endurance, not raw speed. From what I understand, the energy budget of the human body is tuned for 2 things: neurological activity (the energy consumption of which far exceeds any other animal on earth) and endurance. It's what makes us such terrifying hunters... prey can outrun us but then when they invariably have to stop to recover, we eventually just turn up and they have to keep running again. So, any activity where you're cranking the ol' powerhouse up to 120% and going for a run is going to incur a cost, both in terms of energy consumption (which, as the post demonstrates, is slightly more efficient than a fast-paced walk), but then also the resultant metabolic waste which needs to be eliminated, which is a process that takes place during recovery in the 24hrs or so after you've completed your "efficient" 7-minute mile, and I don't believe the article takes this into account. I watched an interesting video recently (I think it was Kurzgesagt?) that talks about the illusion of high-intensity activity vs low-intensity but longer-duration activity.

NoPicklez 2y ago
We aren't talking about sprinting or 120% type running in this debate. We used to catch our prey through running, but not at breakneck speeds. Humans are absolutely made for endurance running, but not at 120% speeds.

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nayuki 2y ago

> 1 MET is 1 kcal/kg/hr These guys need to get with the program and use metric units. For example, the cycling world uses watts per kilogram (W/kg) to quantify an athlete's output. This is the correct unit to use. To help with this, note that 1 MET ≈ 1.162 W/kg.

scotty79 2y ago
Calorie is a part of International System of Units (SI). But I agree it's lame.
- nayuki 2y ago
  The calorie is not part of the current SI. The SI unit that measures the same quantity is the joule (J). Like all SI derived units, the joule is obtained by multiplying or dividing any number of SI base units, without using numeric scaling factors. 1 joule = 1 newton × 1 kilogram = m^2 × kg × s^−2. The calorie measures the same quantity as the joule (energy or work), but 1 calorie = 4.184 joules. SI generally disallows having multiple units that measure the same quantity (e.g. tesla vs. gauss), especially ones that have numerical scaling factors (e.g. 1 bar = 100 kilopascals). Quotes and references: > the kcal is not officially part of the International System of Units (SI), and is regarded as obsolete, having been replaced in many uses by the SI derived unit of energy, the joule (J) -- https://en.wikipedia.org/wiki/Calorie https://en.wikipedia.org/wiki/Calorie > (this page does not contain any mention of the word "calorie") -- https://en.wikipedia.org/wiki/International_System_of_Units https://en.wikipedia.org/wiki/International_System_of_Units > (Section 4: Units outside the SI) (page 29) Examples of other non-SI units: calorie > (page 52) (year 1948) calorie > (Section 2.2: SI derived units) (page 21) SI derived units with special names and symbols: joule | J | N ⋅ m | m^2 ⋅ kg ⋅ s^−2 -- https://physics.nist.gov/cuu/pdf/sp330.pdf https://physics.nist.gov/cuu/pdf/sp330.pdf

two_handfuls 2y ago

A nitpick: the author states that `kcal/kg/h = kcal/kgh`. This is false, because multiply and divide have the same priority and so are applied left to right. The correct way to write this is: `kcal/kg/h = kcal/(kgh)` The actual computations in the article are unaffected.