The real deal with HIIT and Crossfit and why I’ll never turn back

I was catching up with an old friend the other night and we were talking about life, husbands, food, workouts etc. J made the comment that she’s been doing HIIT workouts with weightlifting and “has never felt better”.  I followed with “I don’t know what I thought I was doing before, but it definitely wasn’t working out”… All of this is so true. Both of us are in our thirties, insert gasp here, and have never been in better shape. Now, I didn’t say the “skinniest”, I said better shape. While yes, I am slimmer than I used to be, I am by far the strongest me. I am also sure we are also the busiest we have been in our lives, managing families, jobs and other adult responsibilities. So what gives? What’s all the hype about HIIT and Crossfit type of workouts? I am going to break it down into a few simple points. I will try to stay away from all of the medical jargon and keep in simple.

  1. High intensity high effort intervals burn more calories during the workout. Why? There are several reasons but I will keep to the basics here. The body is fueled by energy in the form of a molecule called ATP. ATP can be made by three main systems that use carbs in the form of glucose and glucagon, or fat. The anaerobic systems, think high intensity short duration, use mostly carbs to fuel the energy transfer and the aerobic system uses mostly fat to fuel the energy transfer into ATP. The aerobic system needs oxygen to function. With interval workouts, you are recruiting all systems at the same time. Basically, you are constantly burning both fat and excess carbs. As these molecules are burned, more energy is created and this represents the “calorie burn” you get in a workout. So yes, while you can burn calories doing a low intensity workout for an hour, you can burn the same amount of calories in half the time doing a HIIT/Crossfit type of workout.
  2. High intensity exercises burn more calories after the workout is finished. This has to do with the EPOC, excess post-exercise oxygen consumption. Simply put, the body has to replenish the oxygen and energy stores it used during your workout. The oxygen debt after a high intensity workout can last for up to 48 hours. That’s 48 hours of extra “calorie burn” after you’ve finished your workout. Holy cow! In a low intensity aerobic workout, the body doesn’t build up an oxygen debt because it is using the same amount of oxygen that you are breathing. Because there is no oxygen debt, the body stops burning calories when the activity or workout stops.
  3. HIIT and Crossfit type of exercises are functional and typically recruit several muscle groups for one exercise. I am half-way through the book “Learning to Breathe Fire” about the start of Crossfit, the mentality of it and the problems with traditional gyms and machines. One of the main points the book has made several times is that using traditional gym machines that isolate individual muscles is not truly effective for strengthening. In the real world, we don’t only use one individual muscle, we use several muscles co-contracting to create a functional movement pattern. This was 100% ingrained in all of us PTs in graduate school…. Function, function, FUNCTION! Our professors would constantly ask us if our treatment plan was functional for our patients. So if we are treating our patients based on functional activity, why wouldn’t we plan our workouts the same way? Sure you can go to the gym and do a few reps on a Quad machine (knee extension) and a few reps on a Hamstring machine (knee flexion) but are those helping you learn the co-contraction to perform a proper squat? Squatting is one of the most functional and most used exercises in daily life. And yet, how many people have you seen do terrible squats? This is why I LOVE HIIT/Crossfit  workouts. They are typically a serious of functional push and pull movements for the whole body. And the carryover is ridiculous. Honestly. I can swing, lift, throw and carry my kids around like they are feathers. The other day, on the way to school, my 2.5 year old fell and I had to carry her, her book bag and lunch all the while, pushing the stroller with my 1.5 year old over a 1/2 mile rocky city street. And you know what, I wasn’t even phased. No racing heart rate, no muscle fatigue and no heavy breathing. I doubt I would have been able to do that before.
  4. All of the workouts are scalable for every body and fitness type. That’s the beauty of functional exercise. Everyone can benefit from doing squats, push-ups, lunges, pull-ups and you can ultimately scale all of these exercises in a way that will equally challenge a pro athlete and a 70 year old grandmother. Take push-ups for example. Can’t do a real one? Cool… lets try them on your knees or against a wall. You are still getting the same muscle activation and the same intensity as a pro athlete banging them out in a pike or a handstand. This enables us to workout together, with people of all fitness levels and still get the same benefit.
  5. The workouts are usually under 30-45 minutes. In a world where time is money and we all have too little time, I want to get as much bang for my buck as possible. And with HIIT/Crossfit, I might as well be a millionaire. I can remember slaving away on the treadmill and elliptical for hours before feeling fatigued and feeling like a got a good workout. Now, in 30 minutes, I am smoked. And smoked in the way that my entire body feels like it got a good workout, I feel great and have a major endorphin rush. I am usually also smoked in the way that I know I put in 100% and probably couldn’t do more if I tried. And man, does that feel good.
  6. And the most important point: THEY ARE FUN! I can honestly say that I look forward to my workouts and truly enjoy them. Yes, I do have days when I am tired and don’t want to go, but once I’m there and in it, I’m IN it. Because of the nature of the intervals, you are always moving and always pushing yourself. Much better than mindlessly spinning away on an elliptical while staring at a TV screen. You are engaged in the process and the intensity of the exercise awakens an entirely different mentality. Another friend and I call it BeastMode. There really is no other way to explain it. And man, is it addictive. The adrenaline rush and motivation you get from putting your body in these crazy situations and intervals is exhilarating. And those of you who haven’t tried it, probably think I am literally nuts. But I promise, I am mostly sane 🙂 Those of you that are fellow HIITers and Crossfitters, you get it. And it’s one of the best feelings in the world.

So what was my point here? Being fit and strong doesn’t necessarily mean hours at the gym. We all have a million and one things on our plates and it’s hard to fit in extra time. But, take the 45 minutes and go for it, I promise it will be worth it.

“The sweat, the time, the dedication, It pays off”


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