Cardio: How much is enough?

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It seems like almost everywhere you go people are giving you opposing opinions on when, how and how long to do cardio. Should you do low intensity for a long period of time? Or should you do high intensity for a shorter period of time? One thing is for certain; we all have our own genetic predisposition that governs how various forms of cardiovascular activities affect us. However, genetics don’t doom or guarantee anything! That is an exercise law.

To help us understand cardio let’s first take a look at the three dominate metabolic pathways. Each one has a purpose and each one affects our strength, endurance, body composition and agility differently.

1) Phosphagen Pathway: This is the first and most powerful of the three pathways. This is the power source of all your explosive maximal efforts: sprints, heavy lifts, or any all-out physical activity lasting less than 30 seconds. At this point you may be saying to yourself  “30 seconds? How the hell is anything lasting 30 seconds considered cardio?” Well, the beauty of this pathway is that the recovery time between intense “bouts” is also very fast because the phosphagen pathway works hand in hand with “ATP” or adenosine triphosphate. Which is just a big scientific word meaning the currency of energy on the body. Basically, we all have a certain amount of ATP cells in our bodies at any given time and after 30 seconds of all-out maximum exertion they’re pretty much depleted, but only for about a minute or two and then our body produces more (of course this varies depending on your current levels of conditioning and could take upwards of 3-5 minutes in the beginning stages of training) . An example of how to put this pathway into action to improve cardiovascular stamina would be a 30 second all-out sprint followed by 1 minute of rest repeated 10-20 times.

Another beautiful thing about this pathway is that in addition to burning fat it does NOT waste muscle but in fact helps to build it! This is due to the intensity of the exercise. Most workouts fall short “waking up” the central nervous system because of their lack of intensity. Intensity is the key because intensity is the signal to your body that a change is needed whether in the form of fat loss or muscle gains. Without intensity (sweating, out of breath, cursing your trainer…) your body happily stays right where it was because it’s already “fit” enough to handle the amount of strength and stamina you require from it. So step it up!

2) Glycolytic Pathway: This is the dominant pathway in intervals of exertion lasting between 30-120 seconds. This is our “mid-distance” pathway and is mainly used in such sports as boxing, 400, 800, and 1200 meter runs or swims, basketball, soccer etc… This pathway also aids in waking up our central nervous system by recruiting a high amount of muscle fibers to complete the task at hand. A two minute on – one minute off approach to running, boxing, burpees, box jumping, rowing etc. about 10 times through is a great way to increase your cardiovascular capacity without having to sacrifice strength and agility. This pathway allows for higher levels of cardio endurance to be reached than the phosphagen pathway through longer intervals of exertion but without all the muscle wasting side affects and the third pathway. Which brings us to…

3) Oxidative Pathway: This, as you may have guessed is the long distance or endurance pathway and the only one that is considered “sustainable”. Meaning that unlike the phosphagen and the Glycolytic pathways which are unsustainable (you can only do em for so long before you fatigue) The oxidative pathway can be trained to go and go. Marathon runners are an example of people who have trained their oxidative pathway to insane capacities. Basically anything lasting longer than two minutes is dominated by this pathway.

So, what is one to do? Which one is the best for me? Answer: They all are. However, here’s something to consider before you lace up your running shoes and set out for that 10k. Although the oxidative (long distance) pathway is conventionally know to decrease body fat it is also considered to be the least functional of the three and wastes the most muscle tissue as well. Studies have shown that high intensity levels of interval training (the first two pathways) burns as much, if not more body fat than long distance training does. Studies have also shown that training in the first two pathways increases ability in the third, however training in the third pathway actually decreases ability in the first and second. Meaning those long runs and bike rides could be the very thing preventing you from getting that sculpted physique we so long for. Need proof? Just compare the bodies of sprinters and long distance runners.

My opinion? Keep the cardio brief and intense (under 30 minutes). Use intervals when you do cardio. Don’t get sucked into the belief that you should be on the treadmill for an hour at the same pace. Warm up, tax your central nervous system, push your limits, and get out. You will get all the benefits of long distance endurance training, all the while expanding and improving your overall strength and ability.

Happy cardioing!

To your health,

Justin Schollard


About Justin Schollard

Health and fitness professional. View all posts by Justin Schollard

3 responses to “Cardio: How much is enough?

  • ucfknight46

    Beautifully explained and extremely accurate! I love my high intensity functional training workouts, and I’m all about sprints 80% of the time with one day a week dedicated to long distance runs or bike! Great post!

  • Braden

    I awyals thought higher intensity but would be interested to see what others think too.References :

    • Justin Schollard

      As with any routine variation is equally important. Setting out for a 5k isn’t a “bad” thing to do. My point is that all too often people rely on endurance training as their primary mode of exercise. Things like plyometrics, calisthenics, sprinting and weight lifting burn just as many if not more calories than endurance training, but without sacrificing strength, agility, balance, power, speed and stamina. Intensity is what gives your body’s unique genetic disposition the impetus to change or adapt to a greater level of fitness.

      Thanks for the comment and for reading!!

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