The truth is that both high-intensity interval training and steady-state cardio are effective in their own ways,” says exercise physiologist Jonathan Mike, MS, CSCS, from Albuquerque.
Steady state and HIIT training are versatile, safe, and convenient ways to develop your cardiovascular system. Though both have similar traits e.g. don’t need too much coaching, can both be done indoors and outdoors with minimal amount of equipment, the two are very different in execution and performance.
Steady State Cardio
Steady state cardio is as simple as performing you cardio at a challenging but manageable rate e.g. 60%-70% heart rate max, for 20 minutes or more. Steady state cardio is aerobic, meaning it requires oxygen and is fueled mainly by fat. It can include running, walking, swimming cycling, rowing among other activities.
High Intensity Interval Training
High-intensity interval training is slightly more complex. It usually derives of performing a set number of exercises at 90%-100% of maximal effort for a set time for example 30-40 seconds per exercise with a set rest after a circuit is complete and repeating this several times often 3-5 rounds. An example of a good HIIT circuit can be seen at the end. HIIT is anaerobic, meaning it doesn’t rely exclusively on oxygen and is fueled by stored carbohydrates. However HIIT does require the aerobic system to restore your body back to normal state after each work interval, hence why you breathe so hard after it.
What Research Shows Us
Research shows HIIT enhances the metabolic machinery in muscle cells that promotes fat-burning and blunts fat production. The Laval University study discovered that the HIIT subjects’ muscle fibers had significantly higher markers for fat oxidation (fat-burning) than those in the steady-state exercise group.
And a study published in a 2007 issue of the Journal of Applied Physiology reported that young females who performed seven HIIT workouts over a two-week period experienced a 30% increase in both fat oxidation and levels of muscle enzymes that enhance fat oxidation.
Also in a study conducted to determine the effects of a 15-week high-intensity intermittent exercise (HIIE) program on subcutaneous and trunk fat and insulin resistance of young women it was found that both exercise groups demonstrated a significant improvement in cardiovascular fitness. However, only the HIIE group had a significant reduction in total body mass, fat mass, and trunk fat. The conclusions of this study showed high intensity interval training three times per week for 15 weeks compared to the same frequency of Steady State Exercise was associated with significant reductions in total body fat.
Which is better?
The main debate is which training option burns more calories or fat. Bodybuilders use steady state cardio to burn away fat gradually while trying to hold on to as much muscle as possible, however, most now use HIIT sessions once every 7-10 days or so to gain that extra edge on the weeks leading up to competition.
Studies suggest that HIIT training is significantly better for burning body fat. A study mentioned earlier conducted at Laval University kept it basic, using two groups in a months-long experiment. One group followed a 15-week program using HIIT while the other performed only steady-state cardio for 20 weeks. Proponents of steady-state training were pleased to hear that those subjects burned 15,000 calories more than their HIIT counterparts. Those who followed the HIIT program, however, lost significantly more bodyfat. A 2001 study from East Tennessee State University (Johnson City) demonstrated similar findings with subjects who followed an eight-week HIIT program. Again, HIIT proved to be the better fat-burner–subjects dropped 2% bodyfat over the course of the experiment. Meanwhile, those who plodded through the eight weeks on a steady-state program lost no bodyfat. (Simplyshredded.com)
All the research would suggest that although steady state cardio does have benefits for the body, HIIT will lead to greater losses in fat loss. The main reason for this would be not necessarily the amount of calories burned DURING the session but after it. After the workout a process called EPOC (Excess Post-exercise Oxygen Consumption) occurs often known as the after burn effect. This is a process of increased oxygen intake to correct the body’s oxygen debt. The higher the intensity of the exercise the greater this oxygen debt is. To restore the body back to normal state it requires energy hours after the HIIT training, it gets this from the breakdown of fatty acids and fat stores. Slow steady state cardio does produce this EPOC effect, however, it is very small and will only last 2-3 hours, and so whatever you burn during the workout will be all you will really burn. However, studies have shown that after HIIT workouts, the EPOC effect can still be found up to 38 hours after the workout – basically your body is burning fat to fuel the restorative processes for 38 hours AFTER your workout.
Talanian, J.L., et al. Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women. Journal of Applied Physiology 102(4):1,439-1,447, 2007
Gorostiaga, E.M., et al. Uniqueness of interval and continuous training at the same maintained exercise intensity. European Journal of Applied Physiology 63(2):101-107, 1991.
Trapp, E.G., et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International Journal of Obesity (2008) 32, 684–691