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When you first start out doing a particular exercise, obviously it's harder than if you've been doing it for a while and your body is used to it. Does that mean it takes more energy, and that you therefore burn more calories doing an exercise when it's new to you, compared to when you're "in shape" for it?

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3 Answers 3

Short answer:

No, you are burning fewer calories than when you are experienced--particularly if you are increasing load.

Longer answer:

Based on my own experimentation with my Polar heart rate monitor I have found that the calories burned is a function of the amount of work being done. The more experienced you become, the more adapted your body becomes to the type of work you give it. Your range of motion improves, the amount of additional load (weight) you can handle also increases, and the amount of work you are doing increases. As you get stronger, you either increase your muscle mass or become more efficient using them. This in turn improves your metabolism, which will burn more calories even while sitting still.

The reason a new exercise is hard at first is because your muscles are not used to working that way yet. You can't use all the potential energy you have until you acquire both the skill (muscle coordination) and strength to do it properly.

The more you work the more you burn.

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Short Answer

No, experienced athletes burn the same number of calories as novices when performing the same action over the same time.

Long Answer

We will use physics to answer this question. In particular, the forumla for potential energy will be of use:

U = mass * gravity * height

Let's take the simple example of lifting a 20 kg dumbbell from the ground to 1 meter high.

U = m * g * h
U = 20 kg * 9.8 m/s^2 * 1 m
U = 196 joules

It takes 196 joules of energy to increase the potential energy of that dumbbell. Where does this energy come from? It must come from somewhere to satisfy the law of conservation of energy.

It states that the total amount of energy in a system remains constant over time (is said to be conserved over time)

The energy comes from the body burning calories. It must burn 196 joules to comply with the law.

1 cal = 4.2 joules
1 kcal = 42000 joules
196 joules / (42000 joules/kcal) = 0.00467 kcal

You burn 0.00467 kcal to move that dumbbell up. (Food items are always labeled plainly with calories, but technically they mean kilocalories). No where in these equations does experience or ease of effort factor in. Arnold Schwarzenegger in his prime will burn 0.00467 kcal and a scrawny kid will also burn 0.00467 kcal to move a 20 kilogram dumbbell up 1 meter. Yes, Arnold will have a easier time because trained muscles store more glycogen and stronger muscle fibers contract. But he cannot defy the laws of physics by burning less calories than the scrawny kid.

Real World

The above assumes that the experienced athlete uses the same technique as the novice. In the real world, this is not always the case. In nearly every sport except bodybuilding, athletes use special techniques to more efficiently use their energy. These techniques channel more energy towards there goals and lets less energy dissipate for other means. For example, I recall in the 2008 Olympics, the announcers said Usain Bolt took on average less steps than his competitors. This allowed him to more efficiently channel his energy towards running fast. His competitors were generating less speed for the same amount of calories burned.

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6  
You falsely assume a 100% energy conversion efficiency, which muscles don't reach. Muscles have an efficiency of 14% - 27%. Your model is way to simplistic. I can hold a dumbbell just straight out in front of me without moving, yet I'm constantly burning calories despite the potential energy staying the same. You give the theoretical minimal amount of energy that has to be used but don't even consider waste heat. In reality you actually you use a lot more energy and the efficiency can actually be increased through training. –  Matthias Sep 11 '11 at 5:08
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I wasn't talking about isometric exercises here. If I was, I would have used this explanation. –  JoJo Sep 11 '11 at 5:16
    
Thanks for the explanation! I think your "Real World" explanation was what I was looking for - I was wondering if, when your body becomes used to a certain sport or exercise, you become more efficient and therefore burn less calories. You think that's the case? If so, if you want to burn MORE calories, would it be better to mix up your routine? –  Lauren Sep 11 '11 at 23:03
    
It depends on if your technique is improving. I trained with a marathon runner and he gave me tips such as lean slightly forward and land with the middle of your foot. Techniques such as these help convert more of your burned calories into movement and less is lost to the ground. So if you use these techniques to run a 6 minute mile VS horrible techniques to run the same 6 minute mile, you will burn less calories. Bodybuilding is a whole separate type of sport where the goal is not to make exercise easier, which is why in my physics explanation I left out energy efficiency. –  JoJo Sep 12 '11 at 0:24
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I wouldn't switch up a routine as the primary way to increase calorie expenditure. It's much better to smartly choose exercises rather than depend on your inefficiency at a new routine to burn more calories. For example, to burn more calories, you would stop doing wrist curls and run a mile instead. You would not switch from barbell wrist curls to dumbbell wrist curls as the primary way to burn more calories. –  JoJo Sep 12 '11 at 0:39

Movement efficiency can be improved though training. How much of an effect this has depends on the form of exercises but generally isn't that big.

But the situation is a lot more complex. Let's say you go running. Over time you might loose some weight, which means you use less energy to run the same distance at the same pace. On the other hand as you get better at running you might run the same distance in shorter time, which uses more energy.

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