This is one of the most common roadblocks you're going to run into with low-carb dieting...

You want to do high intensity interval training (HIIT) because of how effective it is for burning fat.

However, HIIT uses primarly carbs for fuel (i.e. glycogen and blood sugar) and trying to do it while on a low-carb diet with no glycogen reserves is exhausting and, quite frankly, somewhat self-defeating.

If you've tried it, you know you crash out FAST.

So what's the solution?

I've got an excellent guest article here from Matt Stirling, creator of the Customized Carb Cycling Solution that I talked about yesterday, with an answer for you.

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Cyclical Carb Intake for High Intensity Training

By Matt Stirling

Creator of the Customized Carb Cycling Solution

 

Going HAM: Adjusting Carb Intake for High Intensity Outputs

Want to keep muscle and get ripped? Dumb question- of course you do and rightly so. You put in months at the gym bulking up only to lose it all during a prolonged low-carb cutting phase on your way to a skinny fat, flat looking physique just in time for summer. Or maybe you never stopped bulking and now you’re the guy stuck wearing a Billabong wetsuit with no surf board in site come beach time. Where did things go wrong? How could this happen when you planned everything so carefully- bulk all winter and cut all spring had to be fool proof, right? Wrong.

In order to maintain a high level of performance and peak hormonal state, all the while getting cut, you need to trick your body into thinking it is not in a caloric deficit when in it in fact is, and maintain your glycogen stores for when you need to ramp up the intensity of your work outs. Consistently pounding carbs will eventually lead to fat storage and estrogen increases while very low carb intake can have a hellish effect on your ability to stay in an anabolic state not to mention your energy levels and even your libido.

So how do you get the best of both worlds? The best way to accomplish your goal of an ultra-lean and muscular physique is simple: Carbohydrate cycling. Carbohydrate cycling replenishes glycogen in your muscles which your body uses as substrate for adenosine triphosphate synthesis during intense exercise. Adenosine triphosphate, or ATP as you may know it, is the primary source of energy used by your fast twitch muscles during intense bursts of exercise.

Fast twitch muscles are ultimately what you’re going to want to recruit for moving big weights and more importantly getting big results! Classic case in point- look at sprinters and marathon runners:

Sprinting is short and intense necessitating an all-in work effort from your fast twitch muscles. Sprinting, highly recommended as a component of any HIT or HIIT regiment, involves blasting your glycogen stores for fuel. Marathon running on the other hand utilizes slow twitch muscles which as you can see are less powerful yet can sustain low intensity for longer. Which type of physique more closely resembles your fitness goals? Thought so.

Tapping into Your Fast Twitch Muscles’ Potential with HIT

Now for a bit of science behind the workout rhetoric. High intensity training is defined as an exercise that is brief, infrequent and intense. The exercises should be performed with a high level of effort up to 80% or so of your maximum weight. As explained earlier, the idea behind this type of exercise is fast twitch muscle fiber recruitment.

Fast twitch muscle fibers come in two classifications which have distinct energy pathways:

“Histochemical myosin ATPase fiber typing is used to classify muscle fibers as type I or type II, which are known to correspond to slow and fast muscle fibers, respectively. 1

The enzymes that are analyzed reflect metabolic pathways that are either aerobic/oxidative or anaerobic/glycolytic.5 This classification technique leads to 3 fiber types: fast-twitch glycolytic (FG), fast-twitch oxidative (FOG), and slow-twitch oxidative (SO) 2.”

Fast-twitch glycolytic or Type IIX Fibers are primarily activated in this 80% range and are the biggest and most powerful muscle type of the three. Engaging these muscle fibers will help you to put on more raw size and strength than any other type of exercise. The key is supplying your muscles with enough glycogen to do the job, which if you want to stay lean too, can only be accomplished through strategic carbohydrate cycling.

High Intensity Training Relies On WHAT? Carbohydrates!

We’ve established high intensity training most efficiently recruits fast twitch muscle fibers, which are inherently more desirable than their slow twitch counterparts for our purposes of getting JACKED. Now let’s go on to discuss how to properly fuel HIT workouts all the while maintaining that lean, aesthetically pleasing physique you’ve worked so hard on.

The most glycogen-bestowing, insulin inducing fuel available to your muscles is in the form of carbohydrate. Sure your liver can turn some tricks to get you to store a little something from all that protein you’ve been pounding but ultimately, you are absolutely going to need carbohydrates if you plan on maintaining a high level of both intensity and performance during your HIT workouts.

Carb cycling will help get you there by first increasing insulin sensitivity during low carb days. Then when you’re ready to carb up, those fast days will pay huge dividends as your muscles will be more receptive to glucose uptake thanks to increased insulin sensitivity.

“limitation of carbohydrate intake, and an increased proportional intake of protein, and the use of unsaturated fat have each been shown to enhance insulin sensitivity.” 3

HIT will only help by greasing the wheels for even greater levels of glucose uptake by purging your muscles of their glycogen stores. As your body’s glycolytic pathways become more efficient you will be able to store more glycogen which in and of itself will make your muscles appear larger and fuller than ever before.

The Case Against Very Low-Carb’ing

Let’s be clear: carb cycling is 100% carbohydrate restrictive. On days where you eat less carbohydrate you will be replacing them with either protein or fat to get your calories. So why can’t you rely on fats or proteins to do the job for you all the time? The less complicated version is that fats are stored as fats and proteins convert much less efficiently into glycogen, and you undeniably need ample glycogen stores for generating fast twitch power during HIT.

As your HIT work out progresses, there is a shift towards glycogen as the primary source of ATP production shortly after your initial ATP stores are cashed out which happens relatively quickly. Simply put, without glycogen reserves you can expect to crap out pretty quickly.

Secondarily, your body will eventually begin to cannibalize your muscle if you are sending constant signals food is in short supply with your low carb diet. Hence the beauty of cyclical carb intake: there for you when you need it and not when you don’t. The best part is you can even splurge and enjoy some of your favorite high-carb meals without feeling guilty; just remember to be strategic and pay it forward come gym time.

Source:
Pette D, Staron RS. Mammalian skeletal muscle fiber type transitions. Int Rev Cytol.1997 ;170:143–223.
Pette D, Peuker H, Staron RS. The impact of biochemical methods for single muscle fibre analysis. Acta Physiol Scand.1999 ;166:261–277
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1753185/pdf/v059p00539.pdf

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Bottom line, to really get the most out of HIIT training, you have to be strategic about when you do it.

In my experience, doing HIIT training while on a very carb-restricted phase of your diet is not as effective as more moderate to lower intensity cardio.

It's why I tend to do more long-distance loaded carry type cardio when I'm low on carbs. It's lower intensity but still requires a lot of calories to perform, while supplying relatively heavy, constant loading on the body. It gives me the most bang for my buck and it's a fun (if somewhat brutal) challenge.

After I've loaded up on some carbs, THEN I'll do an HIIT session or two to blast the carbs back out of my system and increase insulin sensitivity.

As you can see from the article, Matt is extremely knowledgeable about how carb cycling works and how to make good use of it in your training and eating.

His program is an excellent guide to maximizing your nutrition...building muscle while getting lean.

Learn more about the Customized Carb Cycling Solution here.