This is likely because you are burning the most calories on average per minute swimming than you do in bike or run (almost certain, if not you would be able to crank out 6 hrs swims and 6 hrs bike rides and feel equally exhausted after both, but almost no one can even finish a 6 hrs swim due to glycogen depletion).

Most people just don't swim long or hard enough often enough to know, but it is also why people feel like heros on their 5 hrs rides in training and then 4 hrs into race day in an Ironman after what they think is an easy 1 hrs swim they are totally slowing down. But 1 hrs swim + 4 hrs ride is always harder than 5 hrs ride. But hey, everyone likes to ignore how much the swim takes out of us (because really there is not a good accurate way to measure it deterministically)

This.

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I finished a 90 minute ride outdoors the other night, and my Wahoo Elemnt had NP as 217 watts, kj at 916 and calories at 916. Does that mean that my PM and Wahoo are inaccurate also? I was nowhere close to averaging 250 watts, but I did climb about 1300 feet during the ride.

DO NOT look at normalized power if you want to know energy burned during a ride.

• The kilojoules of energy put to the road is average power x time
• The kilojoules you consumed are essentially 4 x average power x time
• To convert to calories, roughly divide that by four so you are back to average power x time

If your kilojoules were 916 in 90 minutes then your average power

= 916 x 1000/(90 x 60) = 169.6W

NP is a fictitious construct when it comes to physics that roughly tries to convert the variability of your ride into some type of physiological equivalent wattage had your ridden the entire ride pegged at that average power.

To help simplify this, let's say I do 100 kilo bench press 4x 10 reps. According to this I moved 100 kilo x 40 x 0.5m (let's say 50cm is length of my arms) x 9.8m/s**2

The total work here is 19,600 joules

I could also do 20 kilos x 10 sets of 20 reps.

The total work here is 19,600 joules too,

Let's say I spread both efforts over 10 minutes (600 seconds) taking whatever rest I want between sets. Then my average power would 19,600 joules/600 seconds = 32.6 W

As far as physics goes I did the exact same amount of work and use the exact same average power over 10 minutes. It is just how I spaced all that out. Or I could do a single set of 100 kilos 40 reps of I could do 400 kilos x 10 reps

But for me if I did 40 reps of 100 kilos versus 200 reps of 20 kilos I will later feel a lot worse on the set with heavier weights but less often and more coasting/rest in between.

I don't know how you would calculate the NP for the 10x400 kilos set vs vs the 4x10x100kilos set vs the 20x10x20 kilos set, but from first to last the NP would go down.

NP goes up when you concentrate your workload into shorter higher power periods relative to a perfectly evenly spread out effort (ideally in an Ironman AP = NP). If you ever do a really steep hill climb that is 30 minutes of longer you will see your NP and AP will also be identical (your body will self select a sustainable even pace)

You are gonna have to provide at least a shred of real evidence for anyone to believe you on this

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Matt

I can agree with these rough ratios.
For me, similarly intensity workouts in all 3 disciplines result in:
16 Cal/min for swim,
17 Cal/min for ride,
18 Cal/min for running.

In principle, it's pretty much a wash.

Your wording could be a bit less snobby for your ask but let's at least have a reasonable adult discussion rather than get all pompous without offering anything useful.

But how do you measure the mechanical energy applied by the entire body to the water. If you can do that, then we can deterministically calculate between all three sports.

This is why I said "likely". My real world observation of almost everyone handling a straight out 5 hrs ride vs a 1 hrs swim+4 hrs ride (assuming same average wattage for bike leg) suggests to me I am on to something as I have experimented with groups of people (typically 30-75 people) during long training camps. The qualitative observation by and large of the campers has always been 1 hrs swim + 4 hrs bike is always more difficult that straight up 5 hrs ride. I have also experimented on the guys and gals with 90 min swim + 6 hrs bike format. Everyone is crawling and dead at the end of this. When I do 7.5 hrs bike, generally folks are much more chipper.

The other obvious shred of evidence, would be for me to ask you to do three sessions

2.5 hrs swim
2.5 hrs run
2.5 hrs bike

Just go easy in all sports and report back. Once you report back at least we will have he evidence on your body. That would be an N=1. 2.5 hrs should be just enough to get slightly glycogen depleted in an sports. You can only use water for nutrition in all three sessions. No sugar, no electrolytes

There are very few studies which measure o2 and swimming but here’s one on cycling, arm cranking and swimming. In this group swimming is about 20% lower.

For the sake of argument 1L per minute o2 is about 5cal. So someone going pretty well at threshold of 4L is about 4x5x 60 minutes =1200cal.

We’ve done about 500 tests mostly multiple times on the same athlete and only rarely see run values lower than cycling (think cat 1/2 cyclist turned triathlete who can’t run yet)

https://www.frontiersin.org/...phys.2017.00639/full

Maurice

Doing a test to exhaustion is one thing. I was talking about average effort over multiple workouts in a week originally in this thread and then was talking about effort at aerobic levels. I would just eyeball that if you are going at threshold effort, running is going to burn the most due to the weight bearing nature. But at easy efforts, you can really drop the run effort. For swimming you can only go so slow before your stroke rate goes so far down that you're no longer getting enough oxygen. Running you can go slower and slower and slower till you're barely walking.

From the first paragraph of this study:
Oxygen uptake (VO2) kinetics has been reported to be influenced by the activity mode. However, only few studies have compared

VO2 kinetics between activities in the same subjects in which they were equally trained. Therefore, this study compared the V⋅V·O2 kinetics response to swimming, arm cranking, and cycling within the same group of subjects within the heavy exercise intensity domain. Ten trained male triathletes (age 23.2 ± 4.5 years; height 180.8 ± 8.3 cm; weight 72.3 ± 6.6 kg) completed an incremental test to exhaustion and a 6-min heavy constant-load test in the three exercise modes in random order.

Right at the start they have made a fundamentally flawed assumption, i.e. that triathletes ae equally trained in the swim and the bike. I think we all know this is not true, e.g. that tri-guys are much more highly trained on the bike vs minimally trained on the swim. This kind of invalidates the whole study IMO. :)

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"Anyone can be who they want to be IF they have the HUNGER and the DRIVE."

Feel free to scroll down and read a bit more than the opening sentence(s). It expresses o2 consumption as a function of speed.

As I said not a whole of studies but more than this one out there.

ETA: the measured o2 at 2:55 or so per 200 was about 3.7L, for cycling at 350 watts it was about 4.8L.

Maurice

OK, but still the 2:55/200 m swim is a considerably lower level of effort than holding 350 watts on the bike, if the person is really evenly trained in both.

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"Anyone can be who they want to be IF they have the HUNGER and the DRIVE."

Running.

Your not hungry. It is your intestines and stomach pressing back down on your body once gravity is placed back on top of you. If you bike right after or run you will not get this feeling as you focus on other sensor information.

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Technique will always last longer then energy production. Improve biomechanics, improve performance.
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Here is the only study I found that measured energy expenditure data on triathletes in all three disciplines. These are the relationships they determined between speed and rate of oxygen consumption for 55 national-class youth male Czech triathletes (average 18 years old):

Running: Edot = 6.03*v - 2.13
Cycling: Edot = 3.08*v - 10.13
Swimming: Edot = 18.79*v + 5.02

Reference: https://www.persee.fr/...99_num_24_1_2125.pdf

In these equations, "v" is the speed in miles per hour, and "Edot" is the resulting rate of oxygen consumption in milliliters of oxygen consumed, per minute, per kg of body mass. In exercise physiology, oxygen consumption rate scales linearly with "metabolic power", which is the rate of metabolic energy expenditure e.g. calories per minute.

So you can plug in different values for "v" here and see what you'd expect for relative energy expenditure in the different disciplines, or determine the speed in each needed for a certain rate of energy expenditure. For example, an oxygen consumption rate of 50 mL/kg/min would be achieved at a running speed of ~8.6 mph (just under 7:00 mile pace), a cycling speed of ~19.5 mph, and a swimming speed of ~2.4 mph (about 1:10 minutes per 100-yard pace).

YMMV but for me the swimming speed is the outlier here. At more modest pace of 1:30-2:00/100y, Edot for swimming ranges from 37-47 mL/kg/min. Relatedly, these equations are average lines of best-fit. They will vary at the individual level, e.g. my function for running may be 6.63*v - 1.95, yours may be 5.87*v + 0.87, etc.

This is quite useful and at the end of the day the most important thing is actually what your overall body is doing for aggregate work, not what mechanical work gets to the water or road, because the aggregate human body work load is what affects the question at the top of this thread and what affects us in real life (power to the road is a very nice accurate proxity for how much energy my body is consuming per second).

But you point our personal efficiencies in each sport, and this is where Erikmulk was going (and so am I). By and large triathletes have horrible efficiency in the water, so if I tell a group of random triathletes to go and load up on pasta tonight and tomorrow morning ask them to do a 2.5 hrs swim this week, a 2.5 hrs bike next week and a 2.5 hrs run the following week and ask them do all three at whatever pace they want with no nutrition, almost all triathletes will be most spent after the 2.5 hrs swim (because the personal efficiency/proficiency comes into play). And to make it easier and remove the question about muscle glycogen being depleted in arms we can mix it up with breaks for kick, or one arm (I actually use a lot of one arm in 10k swim races, to break it up and change up my strokes with some back stroke too).

This is where you equation for O2 metabolic rate and individual variances will show.

This is at best a very abstract way to support your assertion at best. What does subjective fatigue have directly to do with calorie expenditure and glycogen depletion? Those people could just be "more tired" or "crawling and dead" because they used their whole bodies during the multisport workout vs straight cycling. They could have gotten their nutrition wrong because of the logistics of swim/run. They could be mentally fatigued from an inevitably longer day going from the pool to the bike rather than just setting out on a single ride. You can't draw any conclusions or "likelihoods" from those observations.

It logically follows that high impact, high "gravity" running burns the most calories at a given effort, cycling where your body weight is partially supported burns a little less and swimming, the lowest impact sport burns the fewest. There are studies to support this too, I think even a GTN video on the subject if I recall. I can see a scenario where cycling up a steep climb burns more than running on a flat path and where swimming hard in cold water burns more of course. In "normal" circumstances though, I can't see how swimming is the most (least?) efficient way to output energy.

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It really doesn't matter if someone is "more efficient" at swimming. Just because Phelps can burn more calories than me in the pool because he's stupid fast doesn't mean he won't burn more calories given the same time while running. If he runs slow he's going to be close to his metabolic burn rate of swimming and if he runs fast he will be beyond that.

The difference could be that the swimming and cycling portion could be pretty close.

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Washed up footy player turned Triathlete.

Not sure what the per hour rate would be, but I train about 12 hours per week and go through different phases in terms of proportions for each sport (from a base of S4 B4 R4 I'll vary the weighting for each sport). My training experience has always been: when I am running more, I lose weight and get really lean; when I bike lots, my weight stays level (or even goes up); when I swim lots, my shoulders and upper body seem to to bulk up and I weigh 5-10 pounds more. So if you are swimming over long periods, maybe the extra upper-body muscle-bulk increases the metabolic demands and you feel more hungry?

Thank you! I’d started several responses and backed off each of them. There were so many flaws in the logic I couldn’t formulate a reasonable place to begin.

I did say it is subjective as we have no mechanical way of measuring.

But in general terms, what i am trying to explain that if you do several hours of training (or a reasonbly long workout like a 2.5 hrs workout in each sport), the average intensity will end up highest on the swim because most people cannot swim easy enough to bring down swim intensity during easy swim periods. I was not trying to compare same intensity across sports. I agreed that for the same intensity, more weight bearing will result in more overall energy burned.

All the reasons you point out for the swim-bike workout subjectively feeling harder are somewhat valid, but I ran these camps for something like 15 years and have observations from many athletes, over multiple workouts over multiple years. I know you guys want a contained study, and I can't offer that. Some observations over many years from the real world.

I think you guys need to listen to what Erikmulk is saying. I get that this board will be biased a bit towards bike-run. The down side is triathletes generally under estimate the workload from their swim in races and swim in workouts. It is likely much larger than they give it credit for.

Do the three standalone workouts of 2.5 hrs each to get a better subjective observation removing all other sports. Do them all tapered and rested. You won't be able to get the easiest swim intensity low enough to not get less gassed compared to an easy bike intensity or even an easy run intensity (as you can always walk). Easy swimming at some point you just drown.

Why don't we invent a sport with all three and find out once and for all?

I feel like we've been here before. I recognize that tree.

I think that the bolded part is all we are talking about here, it directly answers the question from the OP. If you agree with that, you spend a lot of words making it sound like you don't.

To my interpretation, no one was ever talking about fatigue or being "gassed", and we couldn't in this context because it is infinitely individual (background, training, physiology etc) and subjective (what is fatigue really?). Some people can run 100 miles without too much issue, some can swim the English Channel and some can ride 50 000km or more in a year, you can't compare or generalize fatigue across distinct sports. Hell, I would be completely wrecked after 30 minutes of pick up basketball but I could ride 200k and mow the lawn afterwards.

All the rest of this about 2.5 hr workouts, camps is interesting but irrelevant to the question. You are so often right and the smart guy in the thread around here but I think this line of argument is not fully conceived.

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I agree that for the same effort more weight bearing will result in more calories burned. But it is a discussion forum not "just answer one question"

What I have been trying to explain (not doing a good job for some), is that when we swim (especially triathletes) we actually use more energy than we think because swim easy effort is much harder than going easy in the other sports, because swim has this minimum effort, and over time, the load from that adds up. So three workouts at the same intensity, I agree with you. I guess I was trying to explain over many hours in a week or a single long swim like at the start of an Ironman, most triathletes likely use their highest average energy in the swim due to how difficult easy swimming is.

Now that I look back and I look a the OPs original question, I know why I embarked on this slant. Its because he asked "on average between all intensities". So it lead by down that discussion. My response was not meant as a competition about who is theoretically most correct. I was trying to relate this to the practical world for triathletes who may underestimate how much the swim is draining them overall.

I'm also suspicious of Peloton power numbers. The one at our gym says I can hold ~280 W for an hour without much trouble. I weigh about 158 lbs so 280 W is already nearly 4 W/kg for me. I wish I had "4 W/kg is an easy spin" fitness but sadly that is not the case.

If we think of this Q in terms of absolutely which burns the most cal on average in a single hour, yes, running wins.

However, since running is "more weight bearing", this means that you can do less of it over the course of days, weeks, and years. Top distance runners run at most around 150 mi/wk; at 100cal/mi, that's 15,000 cal/wk. Top distance swimmers may swim up to 120,000 yd/wk, which at about 250 cal/1000 yd, equals 30,000 cal/wk. Top cyclists at 700 mi/wk times 40 cal/mi equals 28,000 cal/wk. (The 250 cal/1000 yd and 40 cal/mi are my own personal estimates based on long observation of my personal caloric needs.)

So, swim and bike roughly equal vs runners who burn consid less. This is why top college runners watch their diets very carefully vs swimmers who eat "everything in sight". Of course, swimmers are generally bigger people than runners, roughly 50 % bigger if we compare 130 lb runner vs 185 lb swimmer; taking this into account the comparison is basically a wash but OTOH, a 185 lb runner is unlikely to able to run 150 mi/wk w/o injury. Thus in the end, swim and bike win out in terms of what can you burn the most cals with over the long haul. :)

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"Anyone can be who they want to be IF they have the HUNGER and the DRIVE."