Calories burned and Cardio Machines

The WOD today has a 50 calorie row sandwiched between what feels like a million wall balls and deadlifts (this isn’t the workout but bear with me). As you get off the rower you think to yourself, “Sweet, I just burned 50 calories! Now I can eat like two Oreos.” Think again. You may not have burned 50 calories.

What is a Calorie?

A calorie is a unit of energy, just like a meter is a unit of distance. More specifically, a calorie is the amount of energy required to raise 1 gram of water 1°C. If you had 100g of water and wanted to raise it 5°C, you would need 200 x 5 calories (1000 calories). Food calories, though, are kilocalories – calories multiplied by 1000 (think kilometer vs meter). Kcal or Calorie (uppercase C) is also what cardio machines read to you even though they display it as calories (lowercase c), probably to keep things simple.

Calories and food

Way back in the day, Calories were determined by burning a specific food item and measuring the change in temperature of the surrounding water. You may have heard of the laws of thermodynamics. The first law states that energy cannot be created or destroyed, it is simply transferred to something else or lost in the form of heat. Nowadays, calories in your food are calculated more easily as we have come to find out that 1 gram of fat = 9 calories, 1 gram of protein = 4 calories, and 1 gram of carbohydrate = 4 calories. To calculate the total calories in a specific food item, the grams of each macronutrient are added up and multiplied by their corresponding calorie number, then added together.

Calories and You

Your body needs energy in order to support function. Organs, muscle tissues, and all of your other cells need energy to function properly. Notice that body fat does not need energy to function, its just fat. This energy is measured in Calories. The energy a 250 lb man needs to support function is drastically different that the energy a 120lb women needs to support function. This is also why a person with more muscle mass can afford to have a higher calorie intake. Their muscle tissue will need those calories to function properly, while a person of similar weight, but higher body fat will need fewer calories to function. This also extends to exercise. A larger person with more muscle mass will use more energy during a workout than a smaller person or a person of similar weight and less muscle mass. High intensity exercise has also been proven to cause a calorie burn lasting much longer than the duration of your workout. For more information on this, see the Burn vs. Endurance club blog.

Calories and Machines

Most cardio machines have a “calorie” reading. This number is generated based on power production from the user, and a set weight that the brand chooses. Calories on the rower are calculated by taking the wattage (which is measured by how fast the flywheel slows down) and converting it to calories, the unit for how much energy has been transferred into the system.

For example, Concept 2 uses a 175 lb individual to calculate calories on the screen. Metrics they do not use in their formula are your gender, age, height, fitness level, and body fat percentage, all of which factor into the amount of calories you actually “burn”. You likely do not burn the same amount of calories the screen reads. Lets me repeat myself. You do not burn the same amount of calories the machine reads. The Journal of Sports Science says the following formula is how to know how many calories you burned: Calories Burned = [(Age x 0.074) – (Weight x 0.05741) + (Heart Rate during exercise x 0.4472) – 20.4022] x Time / 4.184. Sounds easy, right? Even this formula isn’t precise, as it doesn’t take into consideration body fat %. So, the only way to get a close estimate of the calories you burn is to wear a heart rate monitor that takes into consideration age, weight, body fat % etc. Even then popular heart rate monitors on the market have been shown to have anywhere from 6-15% error. I will link a post about heart rate monitors at the end of this post.

In doing some research, I found an interesting fact about rowing for calories. If person A rows at 2:20/500 pace, and person B rows at a 2:30/500 pace, person A will finish 25 calories 53 seconds faster than person B. The reason is that meters and time are linearly related, and calories and are exponentially related. Rowing hard on calorie rows may be more valuable than rowing hard on meter rows. Thank CrossFit North Harbor for that.

 

Please feel free to comment with any questions or concerns. Hope you Enjoyed!

-Coach Andrew

 

Click here for info on the accuracy of popular heart rate monitors