# When exercising, does the amount of effort determine calories burned or the actual work being done?

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Will an athlete who runs for an hour at moderate pace and is not tired at the end burn more calories than an out of shape person who runs for an hour a way shorter distance but is exhausted at the end?
Assuming both have the same weight and such

What I want to know basically is if your body gets stronger will it need less energy to perform the same amount of work?

In: 1708

In general no, it requires a set amount of energy (calories) to do the same amount of work. In fact, work and energy as physical quantities have the same measurement unit (it’s Joule). However, it is possible that training will make your body more efficient at doing work, so there may be less energy wasted (like on needless movements, or panting etc.) and thus less energy spent overall. But being exhausted does not necessarily mean you’ve done more work.

Being tired/out of breath is a signal that you’re operating at something approaching your limits.

Work is work though. A 200lb person jogging for 100 metres at the same pace as someone weighing 100lbs is going to use roughly twice the energy.

You burn ~30% more calories jogging than walking. But that’s about it (i.e if you increase running speed more the increase in calories burnt doesn’t increase as much).

So walking 1km burns less energy than running 1km. Obvs efficiency comes into it as you get fitter your body becomes better at stuff. For example if your leg muscles are initially weak you may be using other muscles to compensate for the weakness.

Edit: here’s a study about it
https://pubmed.ncbi.nlm.nih.gov/15570150/

I’m not a scientist, but I have lost weight using a weight loss app that tracks calories burned. Since it knows how heavy I am, the distance I traveled, and how fast I did it, it can tell me how many calories I burned during my exercise. I noticed that at around 220 lbs, it takes about 480 calories to run 5 km in 40 minutes, opposed to around 400 calories to run it when I was at 190 lbs, running it in around 35

I may be mistaken, but it seems the question isn’t being answered?

Does a calorie represent the amount of work accomplished outside your body (like, travelling 1K), or the amount of internal work (travelling 1K easily or having to work hard)?

If a pro athlete runs 1K and an average guy runs 1K, did they both burn the same number of calories?

The key points to me are: *”an athlete who runs for an hour”* versus *”out of shape person who runs for an hour”*.

I’ll ignore the comments about “energy” and “work”, because they are loaded depending on your background. For example, if you’re doing a physics math problem running around the block has zero net work because you’re back where you started.

Body efficiency and physical health are major factors. Even if the two people were of similar body weight, the athlete who is strong and in shape will have strong muscles and high body efficiency if they’re a regular runner. Their body is used to the exercise. Their heart works less hard and more efficiently, their muscles are already toned and strong and work more efficiently, they need to breathe less hard, their body won’t heat as much and need to be cooled less, and so on. The out of shape person likely has weak muscles that are out of tone, and their body is not used to the exercise. Their heart must pump harder, their muscles strain more, their breathing will be more labored, all requiring more effort even furthering a core body temperature rise that needs to be cooled, and more.

Because the two ran a different distance your answer is hard to answer. If both decided to run across the same field at about the same time, for the toned athlete it is a short jog, for the couch potato it is a hard run, and the athlete will burn fewer calories both in the doing of it and the recovery of it.

The key concept isn’t the body being stronger, but having a more efficient response to intense aerobic exercises, like running. Your heart and lungs get stronger and are capable of pumping more blood with less energy, that’s called aerobic conditioning.

So yeah, if you train your aerobic conditioning, you’ll be able to do aerobic exercises with less expenditure of calories.

There is currently a study being done in Ireland sort of related to this, essentially the idea being investigated is, a person is on a bike for 60 mins in a high gear (lower rpm but more effort) and a person is on a bike for 45 mins in a low gear (higher rpm lower effort) , the work being done by both is the exact same but for an unknown reason the faster RPM cyclist is using more O2.

The candidates all had maximal VO2 tests to ensure they were fit enough. The number of revolutions were calculated to be equal. The bikes were watt bikes indoors. Basically the only variable was the resistance on the bikes.

I dont know the outcome and its a bit of a tangent to your question but the answer should be that O2 required should be the same but it isnt and they dont know why.

Effort and results vary depending on the machine doing the work. Think of it in terms of cars. An older car that’s not been taken care of will struggle to perform even moderately and consume much fuel doing so. A newer, well maintained car will out perform most older vehicles without consuming as much fuel.
The human machine is the same. Out of shape, older and obese people tax their bodies far more than younger, in shape people while performing the same task. Yes, like cars, age matters for us too… old man sigh. You will burn more calories because you’re less efficient. You will also struggle to maintain that level of effort. Strength and stamina are the signs of a well maintained machine. Strength is a result of the work being done. Stamina is your bodies efficiency which it develops as it becomes acclimated to the work.
I hope this helps.

I’m pretty sure that as you get more coordinated it takes less work (calories) to do the same task. This is why ‘noob gains’ are a thing: you’re not that much stronger, you’re just better at firing all the bench-press muscles in sequence. So someone who’s run 2000 miles in the past year is likely to be better at running than someone who’s never done one.

My highschool physics teacher had a great lesson for this. He had me and my friend go to the bottom of the stairwell and basically race up three flights of stairs as fast as we could. Then he and the rest of the class came strolling up at a relaxing pace while we were panting at the top. (Aside from slight weight differences) We had done the same amount of work and burned the same amount of calories.

>if your body gets stronger will it need less energy to perform the same amount of work?

“Work” is a term from science that equals Force times Distance. If for example you pick up a box and carry it to the other side of the room it will always be the same amount of work done regardless how much or how little you struggle.

However, struggling increases energy cost. Arms shaking, maybe you need to set it down and take a breather then pick it back up. Even the systems for breathing and transfer of energy to muscles require energy themselves.

When running you’re basically the box itself and also the Force moving it a given Distance. The same rules apply, energy spent not on directly completing the task is lost efficiency.

TL;DR: Struggling decreases the *efficiency* of energy spent on the task, therefore increasing the total spent.

Bonus: Levers are interesting in the conversation of work. Remember W=F*D, so if you increase the distance (longer lever) it decreases the force required (less effort) to achieve the same amount of work (rotation).

It is kind of both in some circumstances and not in others. For example, a bike- if you take a 30 min ride on a recumbent bike where you lean your upper body against the back of the seat and just move your legs, you’ll burn slightly less calories than on an upright bike at the same resistance for the same time if you’re engaging your core muscles while doing it, so in that case the effort does increase the outcome. In your example, it’s affected by the persons PRE, which is the perceived rate of exhaustion. you’re probably not as exhausted as your body thinks you are. but if two people were to run the same distance at the same speed, the person with worse cardiac endurance would have a greater payoff.

exercise needs to be a static thing to continually improve. If you do the same exact workout every single day, you’ll improve to a point and then plateau. In order to leave the plateau, you need to increase the duration, intensity, or both of the work out

This is easy to answer. The correct answer is that it is the effort you exert that burns the calories, not the actual distance the weight bar (for example) has moved. Burned calories are expelled as CO2 in our breath, and water as sweat/urine/etc. if two people climb a flight of stairs, and one arrives sweaty and out of breath and the other arrives with nary a change in heart rate, one has burned more calories than the other. Can you guess who?

Most likely you will burn more calories… as muscle burns more calories than fat… your base burn rate is increased.

If you are asking just to satisfy your curiosity, the answer is yes. And to add on, not something easily explained to a 5 year old (or anyone unfamiliar with the subject). Basically, your breathing, weight, stride, familiarity with the exercise, and much more all play a part. A calorie is a measurement of energy, so more work = more calories burned. But the measurement of the work is hard to quantify.

If asking in the context of losing weight or getting in shape, the ELI5 answer is: it doesn’t really matter. Were talking a few hundred calories difference at the most, a small chicken breast is like 500 calories.

I was fat. When I first started running, I could barely run. It took me an hour to go nowhere and I was wrecked afterwards. The weight barely budged.

I pushed myself. I got fitter, stronger, faster… but was still fat.

But a time came when I was fit-but-fat and so I could run haaard for a longer time.. I felt alive after those runs. Energised and ready to go.

It was those hard, fast, alive runs that caused the weight to melt off in just weeks. Everything until then was just prologue.

I could feel my body dealing with the hard, long, fast runs for hours after I stopped… literally just slimming me down.

The slow, ploddy, fat-man runs just had me hurting after and having a sit down.

That’s not science, it’s just what happened. 🙂

From what I’ve heard if you run a mile or walk a mile you burn the same amount of calories. I’m not sure if that’s true

Calories burned walking a mile = 100 /
Calories burned jogging a mile = 100 /
Calories burned sprinting 100m = 6

However, let’s say you sprinted 100m ten times with a minute rest between each Sprint. On paper you burn 60 calories. But this is a FAR greater option for burning fat and expending calories. This is because sprinting increases your RESTING metabolism a lot more. This is called EPOC (excess post-exercise oxygen consumption). The Sprinting example above burns less calories DURING compared to walking or jogging, but for the rest of the day, you are burning a crazy amount of calories and drastically changing your hormones to promote fat loss. After walking or jogging, that’s it. This is why sprinters are always more cut and lean compared to distance runners.