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High vs. Low-intensity cardio, what’s the best for your fitness goals?

Among the top five questions I’m most commonly asked is the question of which kind of cardio is best.  Although I try to give the best answer, an accurate answer is not quite as simple and would take more time than most people want to sit and listen to me.  This article will answer that question and my hope is that by reading this you will be able to understand how to answer that question for yourself.

Let’s begin by defining a few key terms that will set the foundation.

cardio to lose weight and fat

The VO2max

The term VO2max may not be familiar to anyone who has not studied exercise but it is the gold standard of cardiovascular fitness and health among the exercise science world.

VO2Max stands for Maximal Ventilatory rate of Oxygen Consumption.  To simplify it is your bodieoxygen your body can use during exercise not just how much air your lungs can suck in while breathing. It is measured in milliliters per kilogram of bodyweight per min aka ml/kg/min and although it is the gold standard of cardiovascular health, actually calculating your own requires a machine and/or tests.


The METs

MET stands for metabolic equivalent and is used to measure intensity based on the amount of oxygen a person is consuming relative to their VO2max. In other words, a MET is the way we calculate the amount of calories someone is burning based on the percentage of their VO2max they are exercising at.  1 MET  has two values though as I will demonstrate below.


My VO2max = 50 ml/kg/min

1 kcal/min = 1 MET = 3.5 ml/kg/min and


Below is how I would calculate how many calories I would burn exercising at my VO2max for 60 minutes:

1st –  50 (ml/kg/min) ¸ 3.5 (ml/kg/min) = 14.2 METs

2nd– 14.2 METs ´  102.2 kg (Bodyweight in kg) = 1451 calories burned in 1 hour


*Although it is a lot of calories, it is literally impossible to run for longer than even 5 minutes @100% VO2max.  It is important to know the total however and you will see a bit later in this article how that will apply.


high intensity cardio to lose fat


The Hear Rate (HR) and Max Heart Rate (MHR)


Not everyone has access to a lab or machine that will calculate your VO2max.  Luckily we’ve learne how to convert VO2max to percent of Max Heart Rate which is something everyone can calculate by simply using this formula: 220 – (age) = MHR.  My MHR is 194, now you all know my age…

According to the American College of Sports Medicine, exercise at 60 percent of VO2 max corresponds with a heart rate that is 75 percent of maximum, and exercise at 80 percent of VO2 max corresponds with 88 percent of maximum heart rate.


How to apply those 3 ?


Anyone who knows me will tell you I like facts and raw data to prove what is most effective of the “best” way to exercise depending on a person’s fitness goals.

I love studying the science behind because although everyone has an opinion, science has just about filtered through all of the “mysteries of fitness/weightloss/gaining muscle etc..” and really can provide mind blowing answers to simple questions.

Below is a graph depicting which fuel source our bodies when we exercise at different intensities aka percentage of VO2max. A quick look at the graph and you’ll find that as the intensity of exercise increases we use burn less fat and use more carbohydrate otherwise known as sugar.

This graph is great but without the last piece of the puzzle one might mistaken think “Well it’s obvious Cal, lower intensity exercise will burn more fat.” What the graph actual shows is exercising at lower intensities will burn a higher percentage of fat relative to the total amount of calories burned! However, that does not mean it is the most optimal type of exercise for burning the most fat… #waitwhat?


Here is a real life example, using my data in the calculations:

Pretend I want to do cardio for 30 minutes and want to burn the most fat possible hoping to get those washboard chiseled abs for the summer time. Based on the VO2max to MET to Calories burned calculation from earlier I know that if I can exercise for 60 minutes at 100% of my VO2max I will burn 1452 calories total.  Now that we know how the body uses fat and carbs at different intensities the question is “what intensity will be optimal for burning the most fat??”

So based on all the information in this article, I sit down and come up with the table below:


% VO2max % MHR HR


Calories burned in 60 min Calories burned in 30 min Calories from fat Calories from carbs
90 95% 184 1305 653 65 587
80 88% 174 1160 580 116 464
70 82% 164 1015 508 152 355
60 75% 155 870 435 174 261
50 66% 145 725 363 181 181
40 57% 135 580 290 174 116
30 46% 125 435 218 152 65
20 33% 115 290 145 116 29
10 18% 105 145 73 65 7

Table 1


The Result?

The optimal intensity for burning the most amount of fat is at 50% of my VO2max.  Increasing my intensity will decrease the percentage of fat burned but I will increase the total amount of calories burned.  If I decrease my intensity, I will not only decrease the percentage of fat burned but I will also decrease total number of calories burned.


How to apply into your training:


If your goal is to burn fat, exercise at the optimal intensity of 50% VO2max

If you want to lose weight, the higher the intensity of your workouts the more calories you will burn overall.

Don’t forget that supplements are a great addition to your diet and can help you achieve your goals faster ! Check out our article on the top 4 supplements to a leaner body !

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