Calories: Why Your Exercise Choice Matters More Than You Think

A calorie is a measure of energy. The number of calories you burn while completing any given activity roughly reflects how much energy you exert while doing that activity.

The amount of calories burned during an activity, however, can vary from person to person. For instance, a heavier person will burn more calories than a lighter weight person while doing the same activity for the same amount of time.

The number of calories burned also varies drastically depending on the type of activity. Different exercises or daily tasks call upon different energy systems, each responsible for the production of adenosine triphosphate (ATP), which is extracted from the food you eat and is required for the reactions that take place during any muscle contraction.

ENERGY SYSTEMS

There are three basic energy systems:  the phosphagen system, the glycolytic energy system, and mitochondrial respiration.

The phosphagen system, also referred to as the immediate energy system, is active during all-out exercise that lasts 5 to 10 seconds. This includes activities like the 100-meter dash, diving, jumping, lifting a heavy weight, or anything else that requires maximum, short bursts of power.

This system is responsible for the production of immediate energy, and calls upon the other sources of energy for assistance in any max intensity exercise lasting longer than 10 seconds.

The glycolytic system, commonly known as the anaerobic system, is used during moderate to high intensity exercise lasting about one to two minutes. Resistance training is a commonly used example of anaerobic exercise.

Anaerobic glycolysis takes place when oxygen demands exceed oxygen supply and the molecule pyruvate (created during the partial breakdown of glucose) is converted to lactate. This is also known as “fast” glycolysis.

However, when there is enough oxygen supply to meet oxygen demands, the molecule pyruvate calls upon additional energy via aerobic processes. This brings us to the mitochondrial respiration, or aerobic system – or “slow” glycolysis.

The aerobic system is used during prolonged light to moderate intensity exercise. Common aerobic exercises include running, swimming, cross-country skiing and low intensity group fitness classes.

You can most easily recognize the difference between aerobic and anaerobic exercise by measuring your heart rate. The transition from aerobic to anaerobic is often marked by substantial increases in heart rate, muscle fatigue and deep breathing.

If you are truly partaking in anaerobic exercise, you won’t be able to sustain the intensity of the exercise for longer than about one to two minutes. If you’re able to sustain your energy for longer than that, you are most likely partaking in aerobic exercise.

But, of course, as you become more fit, you’ll be able to perform at high intensity for longer durations of time.

WHICH EXERCISES BURN THE MOST CALORIES?

As a general rule, aerobic exercises burn the most calories. This makes sense when you consider the fact that aerobic exercises call upon the most energy systems. And the more energy you exert, the more calories you burn.

That being said, anaerobic exercise can be extremely effective in building muscle mass or overall body strength. And its important to remember that muscle tissue is extremely metabolically active, meaning it uses up a lot of energy (or calories) to maintain its proper function

Note from Luke:  One thing you might be asking yourself is, "but, if aerobic exercise burns more calories per minute than anaerobic exercise, why are so many coaches pushing anaerobic activities like lifting, running hills, pushing a sled and doing KB swings?". One often overlooked aspect of exercise is what happens after. Because anaerobic exercise (specifically lifting weights) causes so much muscle damage and demands so much recovery AND growth, it requires more calories to recover from.  Even though you wont burn as many calories per hour lifting weights as you would running, your calorie demand stays elevated from weightlifting for hours and sometimes days following exercise, whereas running would go back to baseline very quickly.  When we look at our energy demand OUTSIDE of the exercise window, we can see anaerobic exercise as a key part of any fat loss program.

Below is a comprehensive chart breaking down the average calories burned during one hour of several common activities. Notice the different body weights shown; as we said before, body weight impacts calories burned.

This chart was adapted from: Ainsworth BE, et al. 2011 compendium of physical activities: A second update of codes and MET values – a scientific study.

Next weeks blog post will go even more in depth on aerobic vs. anaerobic exercise, specifically analyzing the percent of fat and carbs burned during different exercises – stay tuned!

Sources:

“Calculating Your Calories Burned.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 15 Nov. 2014.

“Energy Usage During Exercise: How It Affects Your Workouts.” Energy Usage During Exercise: How It Affects Your Workouts | Precor.

Healthstatus.com, Inc. “Calories Burned Calculator.” HealthStatus.

Wayne, Jake. “Aerobic Vs. Anaerobic Fitness.” LIVESTRONG.COM, Leaf Group, 6 July 2015.