By Nick Tumminello
Unless you’ve been living under a rock for the last few years, you’re well aware that high-intensity interval training (HIIT) is a hot topic in fitness and sports training. In fact, the American College of Sports Medicine surveyed more than 3,800 fitness professionals to identify the top 20 fitness trends worldwide for 2014, and it was high-intensity interval training that took over the No. 1 spot. Plus, HIIT also remained in the top three on the lists for 2015 and 2016.
Unlike most fitness trends that come and go, HIIT, which pairs performing high-intensity work (exercise) intervals with low-to-moderate intensity work (exercise) recovery phases, isn’t going anywhere because it’s based on a solid foundation of research demonstrating its powerful benefits. Put simply, according to current research, HIIT yields a broader range of health, performance and fat-loss benefits in less time with fewer sessions than the traditional approach of emphasizing continuous, steady-state, cardio exercise.
Improved Fat Burning and Metabolism
A 2008 study published in Applied Physiology, Nutrition, and Metabolism showed that high-intensity exercise sessions over six weeks (three times per week) increase whole-body and skeletal muscle capacities to oxidize fat (i.e., burn fat).
Similarly, another 2007 study published in the Journal of Applied Physiology found that seven sessions of HIIT over only a two-week period of time induced marked increases in whole-body and skeletal muscle capacity for fatty acid oxidation during exercise.
Additionally, steady-state cardio training has not been shown to create nearly the same excess post-exercise oxygen consumption EPOC (i.e., exercise after-burn) effect as high-intensity exercise. This is due to a simple reality of exercise: The higher the intensity, the greater the metabolic impact!
Increased Cardiovascular Fitness
Several research studies have demonstrated that cardiovascular adaptations that occur with HIIT are similar, and oftentimes superior, to those that occur with continuous endurance-based cardio training.
For example, the same 2008 study mentioned above measured VO2 max responses among men and women who participated in an eight-week HIIT program and a continuous cardiovascular training program. VO2 max increases were higher in the HIIT program (15%) than they were in the continuous training program (9%).
You may have heard the term VO2 max. In the book Physiology of Sport and Exercise: 3rd Edition, VO2 max is defined as “The highest rate of oxygen consumption attainable during maximal or exhaustive exercise.”
In other words, as exercise intensity increases, so does oxygen consumption. That said, a point is reached where exercise intensity can continue to increase without an associated rise in oxygen consumption. What we’re really talking about here is aerobic versus anaerobic training, which are two terms that you must understand in order to appreciate the benefits and limitations of cardio training, which is aerobic, and of high-intensity interval training, which is anaerobic.
Put simply, aerobic (training) means “with oxygen,” and anaerobic (training) means “without oxygen.” And, as I just explained, the main thing that separates aerobic from anaerobic training is intensity.
To understand this in more practical terms, here’s a simple, real-world example:
Let’s say you and a friend are jogging together. While you are jogging you are carrying on a normal conversation. If you’re able to speak in normal (full) sentences without any huffing and puffing between words, it means you’re in an “aerobic state” (i.e., with oxygen). However, if you both decide to pick up the pace and speed up to a fast run or sprint, sure you’ll still be to talk to one another, but you’ll be unable to get out full sentences without huffing and puffing, which means you’re now in an “anaerobic state” (i.e., without oxygen). This is your aerobic ceiling or VO2 max.
The example I just gave you is called “The Talk Test.” It’s a very simple but legitimate method of telling whether you’re in an aerobic or anaerobic state.
Now that you understand that the major difference between anaerobic and aerobic training is intensity, it’s obvious that high-intensity interval training is anaerobic training. That said, although you may be familiar with the phrase high-intensity interval training (HIIT), you may not be familiar with supramaximal interval training (SMIT), which many people are actually doing and calling HIIT.
To better understand how to use SMIT— and HIIT, for that matter— you must understand the differences between the two. HIIT involves interspersing high-intensity work (exercise) intervals performed at 100 percent of your VO2 max with either active-recovery (i.e., low-intensity) phases or passive-recovery phases (e.g., standing or sitting fairly still). SMIT, on the other hand, involves interspersing maximal-intensity (all-out) bursts of work (exercise) intervals performed at more than 100 percent of your VO2 max with passive-recovery phases.
Additionally, SMIT may be a more effective training method for active individuals at improving fitness and performance. A 2013 study published in the European Journal of Sport Science looked at the endurance and sprint benefits of high-intensity (HIIT) and supramaximal interval training (SMIT). The researchers in this study found, “improvements in 3000m time trial performance were greater following SMIT than continuous running, and improvements in 40m sprint and Repeated Sprint Ability (RSA) performance were greater following SMIT than HIIT and continuous running.”.
Using SMIT and HIIT Safely and Effectively: General Guidelines
As HIIT and SMIT have grown in popularity, there has been a decline in the popularity of the standard 30-minute bout of steady-state aerobic training (e.g., roadwork or exercise on a treadmill, elliptical trainer or bicycle). However, if you’re just starting (or restarting) an exercise program, beginning with HIIT or SMIT may increase the chance for injury and muscle soreness. According to Len Kravitz, Ph.D. and Micah Zuhl, MS, in their highly science-based paper titled HIIT Vs. Continuous Endurance Training: Battle Of The Aerobic Titans, “Restarting any exercise program requires a careful progression of activity level. Beginning with HIIT may increase the chance for injury and muscle soreness. A better approach is to start with continuous, low-intensity aerobic exercise. A client who can run for 30 consecutive minutes at a moderate intensity can progress slowly into interval training.”
Therefore, it’s probably a good idea to start with low-intensity aerobic exercise until you can run (or use the elliptical trainer or bike) for about 30 consecutive minutes at moderate intensity.
Once you’ve developed a training foundation, when using HIIT or SMIT, you must consider the work-to-rest time interval relationship (i.e., a ratio of exercise to recovery). For example, a 1:3 work-to-rest ratio could be 15 seconds of high or supramaximal intensity work followed by 45 seconds of rest. A 1:2 work to rest ratio could be a 30-second work interval followed by a one-minute rest. The work to rest ratio can vary based on one’s fitness level, personal preferences, training goals or simply to add training variety and take on new fitness challenges.
Lastly, it’s important to note that with both HIIT and SMIT, the more intense (or longer) the (work) interval, the longer the recovery period should be. That said, because SMIT involves supramaximal (all-out) intensity, the recovery period should involve full rest (no activity) between work intervals. On the other hand, when doing HIIT, “active rest” can be used by incorporating low-intensity exercise in the recovery phase.
HIIT: Try Upright Bike or Airdyne Bike Intervals
Although the upright bike and Airdyne are low impact, high-intensity intervals performed on it create a very challenging conditioning workout
Action: Pedal fast and hard at about 90 percent of your maximal ability for 15 to 30 seconds. Rest for 45 seconds to 90 seconds between intervals by pedaling slowly and lightly.
To perform this workout, choose one of the three following SMIT exercise for the parameters described.
SMIT Option #1: Shuttle Run
Set-up: Place two cones 25 yards apart.
Lengths are as follows:
200-yard shuttle run = four round trips between the cones
250-yard shuttle run = five round trips
300-yard shuttle run = six round trips
Between rounds, use a work-to-rest ratio of 1:3 or 1:2, depending on your fitness level. For example, using a 1:3 ratio, if it takes you one minute to complete a 300-yard shuttle sprint, then rest for three minutes before starting the next round. Perform two to five rounds depending on your fitness level.
- You can start your shuttle runs from the starting line. However, I recommend jogging up to the starting point in order to reduce the potential risk of injury that can come from quick starts.
- Drive with your arms while sprinting.
SMIT Option #2: Gasser Run
Set-up: Place two cones 50 yards apart.
Action: Jog up to the start cone, then run as fast as you can back and forth between the cones. Unlike in shuttle sprints, you don’t touch the cones at the turns; therefore, you stay more upright.
Use a work-to-rest ratio of 1:3 or 1:2 between rounds, depending on your fitness level. Perform two to five rounds.
- You can start your gasser runs from the starting line. However, I recommend jogging up to the starting point in order to reduce the risk of injury that can come from quick starts.
- Drive with your arms while running.
SMIT Option #3: Hill Sprint
Set-up: Find a fairly steep hill at least 20 yards long. If you’re lucky, you’ll find one that is 40 yards or even longer.
Action: Run up the hill as fast as you can, then walk down slowly to set up your next run.
Use a work-to-rest ratio of 1:3 or 1:4 between rounds, depending on your fitness level. For example, using a 1:3 ratio, if it takes you 20 seconds to complete a hill sprint, then rest roughly 60 seconds before starting the next round. Perform five to 10 rounds depending on your fitness level.
- Do not take short, choppy steps; take a full stride on each step.
- Drive with your arms while running.
- To vary your leg movement, you can walk backward down the hill between sprints.
Thompson, Walter R. Ph.D., FACSM. ACSM’S Health & Fitness Journal: November/December 2013 – Volume 17 – Issue 6 – p 10-20. http://journals.lww.com/acsm-healthfitness/Fulltext/2013/11000/Now_Trending__Worldwide_Survey_of_Fitness_Trends.5.aspx
Daussin FN, et al. Effect of interval versus continuous training on cardiorespiratory and mitochondrial functions: relationship to aerobic performance improvements in sedentary subjects. Am J Physiol Regul Integr Comp Physiol. 2008 Jul;295(1):R264-72.
Perry, Christopher G.R.; Heigenhauser, et al. (December 2008). “High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle”. Applied Physiology, Nutrition, and Metabolism 33 (6): 1112–1123.
Talanian JL, et al. Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women. J Appl Physiol (1985). 2007 Apr;102(4):1439-47.
Bahr R, Sejersted OM. 1991. Effect of intensity of exercise on excess postexercise oxygen consump- tion. Metabolism, 40(8), 836-841.
Helgerud, J., et al. 2007. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc, 39 (4), 665-71.
Wisløff U, et al. High-intensity interval training to maximize cardiac benefits of exercise training? Exerc Sport Sci Rev. 2009 Jul;37(3):139-46.
Micah Zuhl, MS, Len Kravitz, PhD. Hiit Vs. Continuous Endurance Training: Battle Of The Aerobic Titans. IDEA Fitness Journal » February 2012. http://www.ideafit.com/fitness-library/hiit-vs-continuous-endurance-training-battle-of-the-aerobic-titans
Wilmore JH and Costill DL. (2005) Physiology of Sport and Exercise: 3rd Edition. Champaign, IL: Human Kinetics
Endurance and sprint benefits of high-intensity and supra-maximal interval training. Cicioni-Kolsky D, Lorenzen C, Williams MD, Kemp JG. Eur J Sport Sci. 2013 May;13(3):304-11.