Ok, spoiler alert, this post is me geeking out a little bit about training intensity, (concerning cardio) and while I find this kind of stuff pretty cool for some reason not everyone else does (heads up, not a good topic for your typical night out….)

How Our Bodies Create Energy And Allow Us to Exercise/Do Pretty Much Anything (i.e. The 3 Energy Pathways)

Keep in mind that the process of creating energy is way more complicated than this, but essentially the body converts substances within our body (such as food) to useable forms of energy and in order to do so there needs to be oxygen (among other things) present. Our bodies have 3 different methods of creating energy and the one we use at any given time depends on the energy requirements of the activity we are doing at that moment. The Three Methods (pathways) are…

  1. The Phosphagen Pathway: fuels intense exercises which are only sustainable for up to 30 seconds (think maximum effort sprints)
  2. The Glycolytic Pathway: for when we engage in moderate-to-high intensity exercise lasting approximately 2 and a half minutes but not longer (running around a 400m track for time)
  3. The Oxidative Pathway: for low-to-moderate intensity exercises that can be sustained for long periods of time (running a 5k, a 10k, a half marathon….you get the idea)

The Energy Pathways

What This Means RE: Cardio & Training

The first two pathways (Phosphagen and Glycolytic) are anaerobic, meaning that they use oxygen quicker than our bodies can supply it (not that our bodies don’t try, think back to your breathing last time you did some sprints). It is because the demand for oxygen exceeds the available supply that exercising at this level of intensity is not sustainable. Activities like sprinting are not sustainable and quickly result in fatigue, but by exercising at near maximal intensities we train our bodies to be not only stronger and but also more capable of generating explosive speed and power.

The third pathway (Oxidative) is aerobic, which means that the rate it uses oxygen is equal to or less than the rate at which our bodies can supply it. Training at lower intensities (running at a steady sustainable speed) is effective for building endurance, but does not increase (and in excesss can actually decrease) strength, speed and explosive power.

Ok, so whats the deal? Training hard and fast will increase speed and strength, while going slow and long will create better endurance, but what if I want both? By using high intensity interval training (short intervals of maximum effort ‘sprints’ with periods of rapid recovery) its possible to not only increase strength, speed and power but also improve endurance.

How High Intensity Interval Training (HIIT) Works

The short bursts (sprints) target the anaerobic pathways (thus increasing strength, speed and power) and because there is a recovery period the body is able to replenish the depleted oxygen stores, making another max effort sprint possible (what fun). By repeating this combination of sprint/recovery multiple times (rather than doing single sprints) you will start to target the aerobic pathway as well and as a result BAM increased endurance (and sore legs, but hey that’s only temporary).

Bottom Line

I’m not saying that whatever you are currently doing now is worthless as exercise, chances are you’re doing “x” because you enjoy it and if it makes you happy its worth it. Nor am I implying that I run sprints ever day, that would be a lie (I wish I could motivate myself to do that but I can’t). What I’m trying to get at is that if you love running long distances (or biking for hours etc.) you need to switch it up with some short/intense session, if you want to see real results and keep your body from plateauing. Repeating the same training method every day allows the body to adapt and become more efficient which means that the running the exact same distance will produce increasingly unimpressive results.

Don’t get me wrong, I love running, and not sprints I don’t particularly enjoy those. What I like is going for hour-long jogs because it lets me clear my head, run off a bad mood, or visualize and mentally prep for upcoming competitions. Running makes me happy and If someone tried to tell  me “no running unless its sprints” I would not be impressed and my response might not impress them either. However, I understand that this form of training is ineffective and will not get me the results I want to see; which means that I do not classify it as training, it is something I do on my ‘active rest’ days.

Take a moment to think about what it is you hope to accomplish with your workouts, and if you want real results and improvements, consistently running the same distances at a constant pace is not going to cut it. 

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1 Comment

The Crossfit Exercise Prescription pt 1 - Constantly Varied: Varied vs Random | Blonyx Blog · August 8, 2013 at 5:07 pm

[…] that are specifically designed to hit each of energy pathways: phosphagen, glycolytic and oxidative (i.e. short sprints, medium length WODs, and the longer […]

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