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If you want to lose body fat, should you choose high intensity interval training or steady state cardio?
This question has been the cause of many-a heated debate within the fitness community. Luckily advances in exercise science have helped us add scientific data to back up claims made by both parties. Below we will take a look at the differences between high intensity interval training and steady state cardio to answer the question “Which method is best for fat loss”?
Let’s define steady state cardio as any single mode exercise, performed at low intensity, for a period of greater than 20 minutes. On a scale of 10 you would give steady state cardio an exertion rating of 3 or 4.
Steady state cardio fails to elicit a stimulus great enough to involve any of the fast twitch muscle fibers. During a long bout of cardio intensity levels remain low. You recruit only slow twitch muscle fibers. Slow twitch muscle fibers also happen to be the weakest of the muscle fibers and make up the smallest percentage of muscle fibers in your body.
Your body is unable to fire random muscle fibers and will activate your slow twitch fibers first every time…until the stimulus is too great. This is known as orderly recruitment. During steady state cardio the stimulus is never great enough to activate any of the fast twitch muscle fibers. The body burns only enough calories necessary to sustain a low intensity, long duration event (ie… jogging) for as long as the event occurs. As soon as the event is over so too are the burning of calories. This is a survival mechanism that is hard wired into every human.
Due to the low intensity steady state cardio places very little metabolic demand on your body. It does nothing to increase BMR (Basal Metabolic Rate→the amount of calories you burn at rest) and the caloric burn is over almost as soon as the event is.
←You can see the difference in musculature between sprinters and long distance runners
For a more indepth look at the science of SST and HIIT checkout “Body by Science”
Let’s define an event as high-intensity if you rate the exertion level at a 9 or 10. I’m talking immediately after the event is done you are on the verge of puking or crapping your pants. That’s high intensity! I know that isn’t the scientific answer, but that is how I define an event as high-intensity.
High intensity interval training burns a large amount of calories during the event. The stimulus is great enough to recruit the large and powerful fast twitch muscle fibers. Fast twitch muscle fibers (due to their large nature) have more space to allow glucose to enter which improves insulin sensitivity.
Another big difference between steady state cardio and high intensity interval training is the stimulus produced during bouts of intense exercise causes the body to continue to burn calories at an elevated rate for hours after the event is over.
Numerous studies have shown that the body can burn calories at an elevated rate for up to 24 hours. Imagine being able to sit on the sofa after a hard workout and know your body is still devouring calories faster than a fat kid devours left over birthday cake.
High intensity interval training is shorter in duration, yields a greater post exercise caloric burn, and will help you shed fat at faster rate than steady-state cardio. If fat loss is your goal I would highly recommend adding 1-2 days/week of high intensity exercise to your workout regime.