In my previous article about cardio, I explained the differences between HIIT and LISS cardio training. After more extensive research and actually understanding what does what for the body, I’ve come to the conclusion (with the help of all the articles, studies, and forums I’ve read) that cardio should be performed as HIIT. Traditional cardio is used by many to help shred up and lose fat. This is obvious, but an underlying terror hides beneath the layers of fat. Cardio will actually decrease your overall muscle mass if performed in the traditional manner! With traditional cardio (LISS – Low Intensity Steady State), your metabolism actually decreases. Initially you will have a good weight loss bump during the 1st two weeks, but your body’s metabolism will adjust as a survival mechanism to prevent starvation. The traditional cardio that I am referring to consists of uphill walking, light jogs on the treadmill, or even the elliptical. Basically anything attempted for a long period of time at a steady state, or trying to keep your heart rate in a particular range. What you need to remember is that muscle is adaptable! In a sense, it’s very plastic. If you train to be a power lifter you’ll get great strength, if you train to be an endurance athlete your muscles will adapt for endurance. I made the comparison of marathon runners versus sprinters in the previous article. Just look at the difference in their bodies. Marathon runners have adapted more slow twitch (type I fibers) where sprinter developed more fast twitch (type II fibers) in their bodies. Type II is what bodybuilders strive for as they are thicker, more explosive fibers then their skinny cousin (Type I). Why does this happen? Let’s look at it from an evolutionary sense. With long endurance, your body will require plentiful amounts of oxygen to be flushed around the body. So you don’t want to have more muscle tissue that requires more oxygen. The adaptation lies within losing that extra tissue so your body doesn’t have to work extra hard for that extra oxygen to be pushed around. Some studies found that engaging in cardio actually blunts the speed of contractions within the muscle fibers. This will lead to the development of more Type I fibers. Just think about it, if your one a treadmill for 45 min walking at a slow pace, you’re telling your muscles “this is what they need to adapt to.” So what do they do? Overtime they become acclimated to the type of cardio you are engaging in. So why is HIIT better overall? First, let’s look at the science. The science of it lies within AMPk. ATP is the energy carrier of the cell and when you deplete ATP it becomes ADP then AMP. AMP Kinase is the energy censor of the cell. When ample amounts of AMPk are available this shows a low energy status of the cell which will activate AMP Kinase. When AMP Kinase is activated, it shuts down protein synthesis by inhibiting (mTOR). Traditional cardio is responsible for drastic amounts of AMPk that will shut off your protein synthesis in your muscle cells. When doing cardio you are shutting down you protein synthesis, when doing resistance training you are turning it on, so what you have here is competing molecular adaptations. HIIT training on the other hand acts more like weight training explained in the next paragraph. Now let’s look at the benefits. The metabolic effect of HIIT is in our favor. HIIT has been shown to increase the mitochondrial (fat burning organelles of the body) density and oxidative capacity in you muscle tissue. This means that you have a greater capacity to lose fats as HIIT provides a mass amount of mitochondria. HIIT also raises metabolism for hours after as it increase mitochondrial density to use more fat throughout the day compared to LISS which actually lowers your metabolic rate. Finally HIIT is said (when done correctly) to give you muscles a massive pump. Swelling of a muscle has been directly correlated to the stimulation of growth. When you engage in short, explosive reps, you are mimicking the short intense reps of weight lifting. Since resistance training increases protein synthesis and HIIT mimics resistance training, you will have more protein synthesis with HIIT then with LISS (actually turns off protein synthesis) When attempting this HIIT cardio, you shouldn’t be able to do more then 20-30sec per rep. If you can, then you’re obviously not pushing yourself hard enough. These reps will physically drain you to the point of exhaustion and even vomiting if done correctly. You know you’ve done correct HIIT when you’re on the floor gasping for air finding some way to get your last rep in. In my next article I will explain how to do HIIT the right way and provide examples on what to do.
Vincent Russo, 25 years old from Kenilworth NJ. Has a BA in Biology from Fairleigh Dickinson University in Madison NJ. A Bodybuilding.com Team Athlete, Silver Model, High School Football Coach, Teacher, Waiter/bartender. Was a top 5 finalist out of 500 guys for bodybuilding.com‘s 2012 BodySpace Spokes Model. Compete in the Men’s Physique category where in recent competitions placed 2nd in NPC East Coasts (Nov. 2011), and 3rd in Bodybuilding.com‘s BodySpace Spokes model competition (LA Fit Expo 2012).