HIIT: Is it all it’s hyped up to be?

By Andrew Taylor and Kathleen Wright

 Figure 1.  Women participate in a HIIT class.

How many of us have said we would go to the gym, only to realize later that we don’t have the time? High-intensity interval training (HIIT) classes have increased in popularity over the last few years, partly because the sessions are shorter than traditional workouts. HIIT workouts alternate short (20 or 30 second) intervals of maximum exertion with periods of rest or low-intensity exercises. Elite athletes might take part in HIIT to improve their aerobic energy metabolism and performance. If you have ever played a demanding sport, you have probably been subjected to HIIT during the game or practice. The recent obsession with HIIT raises the question: is it just a fad, or will it stick around as an effective means of exercise?

HIIT can be defined as brief exercise that generates a VO2peak, or 90% of the maximum VO2 potential, commonly followed by a relaxation period. This study utilized the Wingate test: participants repeated 30 seconds all-out maximal cycling on a specialized ergometer, with 4 minutes of recovery in between, for a total of 2 to 3 minutes of intense exercise. The authors focused on specific markers in skeletal muscle metabolic control; they determined an increase in skeletal muscle oxidative capacity after 2 weeks of HIIT. They also found that changes in carbohydrate metabolism (Figure 2) were comparable to adaptations from endurance training. Although exercise performance improved, there was no measurable change in participants’ VO2peak after 2 weeks of HIIT. However, this study did not fully investigate how HIIT affects the cardiovascular and respiratory systems, or metabolic control in other organs.


Figure 2. Results depict the glycogen content, or resting carbohydrate dry weight, found in skeletal muscle during rest and 20 minutes after exercise, both before and after 2 weeks of HIIT.


Additional HIIT data concerning VO2peak and citrate synthase activity support the previous claim that HIIT provides similar benefits to endurance training. This review recognizes that Wingate-based training may not be tolerable for everyone, and instead tested low-volume HIIT. The authors found that their model was time-efficient and effective in producing cardiovascular and skeletal muscle adaptations. They reference the results of similar studies, saying that HIIT is superior to moderate-intensity continuous training (MICT)  in increasing cardiorespiratory fitness and endothelial function. However, researchers still don’t know what intensity or training volume is required to be effective.

A study concerning overweight and obese adults found that HIIT had similar results to MICT, in terms of body composition measures, but HIIT required less training time. They concluded that HIIT may be a time-efficient way to manage weight. Meanwhile, this systematic review determined that MICT and HIIT provide similar benefits for body fat reduction, but HIIT was no more time-efficient than MICT.

The data from these studies indicate that HIIT is comparable to MICT, similar to the difference between traditional and functional workouts, as described previously in this postHigh intensity workouts can be very demanding, as seen with the Wingate test, and may not be suitable for all individuals. HIIT should not be substituted for specialized athletic training, but can be beneficial for athletes who need to quickly use their bodily carbohydrates. Many HIIT studies are short-term, like the first study we mentioned, and further research needs to be conducted to determine the long-term effects of HIIT on cardiovascular and respiratory systems. Although HIIT attracts people with the allure of getting fit fast, there isn’t enough data currently to support that HIIT is actually more time-efficient than endurance training.

Questions to Consider:

Should HIIT workouts be recommended for the average person?

Why could an increase in glycogen dry weight be considered important for exercise?

How could your current workout routine benefit from HIIT?

What athletes do you feel would benefit most from HIIT?

Recommended Further Reading- Works Cited

  1. Figure 1. HiiT_40-20_6108. Attribution: Cathe Friedrich. https://www.flickr.com/photos/cathefriedrich/albums/72157622565339997 [CC BY-NC-ND 2.0 (https://creativecommons.org/licenses/by-nc-nd/2.0/)]
  2. Gibala, M. J., & McGee, S. L. (2008). Metabolic adaptations to short-term high-intensity interval training: A little pain for a lot of gain? Exercise and Sport Sciences Reviews, 36(2), 58-63. 10.1097/JES.0b013e318168ec1f
  3. Gibala, M. J., Little, J. P., MacDonald, M. J., & Hawley, J. A. (2012). Physiological adaptations to low-volume, high-intensity interval training in health and disease. The Journal of Physiology, 590(5), 1077-1084. 10.1113/jphysiol.2011.224725
  4. Wewege, M., van den Berg, R., Ward, R. E., & Keech, A. (2017). The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: A systematic review and meta-analysis. Obesity Reviews, 18(6), 635-646. 10.1111/obr.12532
  5. Keating, S. E., Johnson, N. A., Mielke, G. I., & Coombes, J. S. (2017). A systematic review and meta-analysis of interval training versus moderate intensity continuous training on body adiposity. Obesity Reviews, 18, 943-964. 10.1111/obr.12536

CrossFit vs. Bodybuilding, Apples to oranges or two sides to the same coin?

Recently workout fads have been popping up all over mainstream media and in different fitness centers. Everyone seems to have the ultimate plan to burn fat and build muscle, these routines have become more intricate and choreographed, often requiring a coach or instructor to oversee the work out. Older workout conventions have had to adapt to meet the changing needs and desires from society. We are here to figure out, is CrossFit the ‘glow up’ of Body building or are these two style of exercise completely unique?

First, what are CrossFit and bodybuilding?

Example of a typical CrossFit exercise

CrossFit is recognized as one of the fastest growing high intensity functional training regimens to date, popping up in 142 countries worldwide. But what is this mysterious new fad and does it actually work?  The purpose of CrossFit training is to get as ‘fit as personally possible’, but is not specifically focused on just one fitness area. CrossFit aims to optimize physical ability not only in strength, but in cardiovascular endurance, flexibility, power, speed, coordination, agility, balance, and accuracy as well [1]. This lead trainers to develop a plan that incorporates multiple training theories into one ‘Workout Of the Day’ to keep a variety of fitness elements working.These workouts involve elements from gymnastics, weightlifting, and cardiovascular exercises which are performed quickly with little rest between sets.

The goal of Bodybuilding (muscle specific) training is so lose as much fat content as possible while maximizing your bodies muscle mass. This kind of training is where terms like ‘leg day’ and ‘back day’ came from, it is devoting an entire workout to a few muscle groups and working them to exhaustion. When you undergo this type of training your body experiences hypertrophy of all muscle fiber types.[2] A bodybuilding workout focuses on keeping the heart rate steady and high weight low rep exercises to slowly break down and rebuild one’s muscle fiber. This is proven to be an effective method if one is only worried about shear size and growth of muscles [3].

Expected muscle growth of Bodybuilders

After hearing this do you believe they are the same? Here’s what science said.

The approaches of these two exercise styles are most definitely unique, but are the fitness results actually all that different? In one research study called “Functional vs. Strength Training in Adults” 101 subjects, averaging an age of about 55, were separated into two groups that each performed 24 sessions of (functional or strength) training protocol twice per week. Each subject was assessed before and after the study using a quantitative Y-balance test and a qualitative Functional Movement Screen test. The changes between pretest and post test were analyzed and results showed that there were no significant differences in improvement between the training protocols as a whole. However, functional training was less effective for women compared to men in the same group [4]. The variability in prior athletic training must be taken into consideration when interpreting these results. Some participants may have needed additional training to better their basic skills before partaking in these specific training protocols. 

Another study looked at ‘The effects of high-intensity intermittent exercise(HIIE) training on fat loss and fasting insulin levels of young women”[5] comparing the effects of CrossFit(HIIE) training to steady state weight lifting over the course of 15 weeks(exercising three times a week). While this study focused on insulin levels they reported a variety of information on lean body mass, fat content, and weight loss that can be used to draw conclusions about the exercise types as well, see that diet was not changed between the groups. This study showed that women who underwent the CrossFit style training showed a significant decrease in total body mass(they lost more weight) 3.5kg weight loss, compared to  the steady state weight lifters who showed a 0.5kg increase in body mass. Demonstrating that while CrossFit participants and bodybuilders may both be used for strenuous high demand exercise, CrossFit is a more effective method of losing weight whereas bodybuilding promotes the act of ‘bulking up.’ While this study was full of information, it does not completely validate the idea that Crossfit and Bodybuilding are the same results with a different method it does help share some information that can point future studies in the right direction.

Based on what we have found we can draw a similar conclusion to previous posts about these training styles. We concur with the groups from previous years that current studies show that while the methods of achieving a lower fat content are different, the overall outcomes of the training types are very similar. In order to better compare these two very different approaches to fitness, there needs to be more extensive research done. The current scientific literature related to CrossFit specifically is lacking. Few studies with high level of evidence at low risk of bias have been widely recognized [1]. As of now we cannot truly compare this new workout fad to the traditional bodybuilding without more extensive studies with conclusive evidence.

By; Ellen Dudzinski and Destiny Neumann

Questions to consider:

  1. Are CrossFit and bodybuilding the only ways to build muscle quickly and effectively?
  2. Is CrossFit or bodybuilding for everyone, why or why not?
  3. What athletes should attempt at least one of these training types?
  4. After reading this, how would you further evaluate the similarities and differences between CrossFit and bodybuilding?
  5. Would supplementation increase the results from either training style?

Suggested Readings:

Karavirta, L., M. P. Tulppo, D. E. Laaksonen, K. Nyman, R. T. Laukkanen, H. Kinnunen, A. Häkkinen, and K. Häkkinen. “Heart rate dynamics after combined endurance and strength training in older men.” Medicine and science in sports and exercise. July 2009. Accessed March 06, 2018. https://www.ncbi.nlm.nih.gov/pubmed/19516157

Aagaard, P., and J. L. Andersen. “Effects of strength training on endurance capacity in top-level endurance athletes.” Scandinavian journal of medicine & science in sports. October 2010. Accessed March 06, 2018. https://www.ncbi.nlm.nih.gov/pubmed/20840561.

Fitts, R. H., and J. J. Widrick. “Muscle mechanics: adaptations with exercise-training.” Exercise and sport sciences reviews. Accessed March 06, 2018. https://www.ncbi.nlm.nih.gov/pubmed/8744258.

Fitts, R. H., D. R. Riley, and J. J. Widrick. “Functional and structural adaptations of skeletal muscle to microgravity.” The Journal of experimental biology. September 2001. Accessed March 06, 2018. https://www.ncbi.nlm.nih.gov/pubmed/11581335.



Have you ever found yourself at the gym on an elliptical or treadmill wondering if there was better and faster way to do cardio for fat loss? A new style of training known as high intensity interval training (HIIT) might just be your solution. Many fitness bloggers who advocate HIIT say that it is better than moderate intensity steady state (MISS) cardio because it burns more calories in a shorter amount of time as well as increases your metabolism and burns calories even after you are done working out due to something called the EPOC effect. On the other hand, there are some people who say that moderate intensity steady state cardio is better than HIIT cardio because MISS primarily uses lipids as a fuel source, and therefore burns more fat. But is one really better than the other?

In 1996, Dr. Izumi Tabata performed a study on the effects of moderate intensity training and HIIT, in order to better understand which method was more effective for preparing olympic athletes for events. For his experiment, he studied two groups. The first group exercised at 70% of their VO2max  five times a week on a treadmill. He compared this protocol with the Tabata protocol and found that the Tabata group was exercising at an intensity of 170% VO2max.  In the end, the two groups both had increases in aerobic capacity, but when anaerobic fitness was analyzed, the Tabata protocol group increased by 28% while the other group remained the same.  This means that high-intensity interval training actually improves both anaerobic (muscle building) and aerobic (fat burning) body systems, while moderate intensity exercise only improves the aerobic system. Additionally, the Tabata group lost more weight on average and gained more muscle than the MISS group. The results obtained from this study ultimately helped legitimize a movement away from chronic cardio and toward high-intensity workouts.


HIIT is a type of training in which intensity and heart rate is varied throughout a workout, as opposed to MISS which is exercising on a treadmill, elliptical, etc. and maintaining your heart rate around 125 bpm for 30 to 60 minutes. During the high intensity intervals, your heart rate should be around at least 160 beats per minute, and during the low intensity intervals around 100 bpm. A typical HIIT workout might look something like this:

Exercise 1: Push-ups

Exercise 2: Jump Squats

Exercise 3: Burpees

Exercise 4: V-ups

Start with push-ups. Perform them for 20 seconds at a high-intensity. Rest for 10 seconds, and then go back to doing push-ups for 20 seconds. Once you complete eight sets of push-ups, rest for one minute. Next, move on to jump squats and repeat the sequence of 20 seconds on, 10 seconds off. Once you finish eight sets of jump squats, rest for one minute, and then do burpees. After burpees, finish the workout with V-ups.

EPOC: Excess Post-Exercise Oxygen Consumption

Since you burn roughly the same amount of calories during a HIIT and MISS workout, The big debate over HIIT vs MISS cardio for fat loss comes down to how many calories you burn after a workout. Most of the misinformation circulating around HIIT vs MISS cardio is centered around EPOC. This term simply refers to the process of restoring your body to a normal resting state after exercising. During this time, your body uses energy and burns calories while recovering and building muscle. The big debate is whether the EPOC after doing a HIIT workout has significant effects on weight loss or not. One fitness blogger said that “new age Tabata style workouts burn 50-70 calories during a workout and 300-400 post workout over the next 24 hours.” The truth is, you are more likely to burn around 300 calories during a HIIT workout and about 40 after. The claim made above would require an EPOC of over 100%, and since EPOC generally doesn’t surpass 30%, this claim was clearly not based on scientific evidence, and can be very misleading to uniformed readers. One study  reported an EPOC of 25% after a very intense and strenuous high intensity workout and 10% after a moderate intensity workout, but even though high intensity workouts have a higher EPOC than moderate intensity workouts, the amount of additional calories burned due to the EPOC effect is not very significant. It is important to keep in mind that although these numbers may appear to be convincing, the difference in calories burned, is only about 30 calories, which is much easier to achieve simply by dieting.

Even though the EPOC theory turned out to be false after all, one study  did show that HIIT training increases muscle mass and therefore increases the capacity to burn fat, so in the long run, HIIT could actually be booting your metabolism.  HIIT also has a lot of other health benefits to offer. For example, one study found that HIIT training greatly improved cardiovascular endurance and that subjects who went through two weeks of HIIT training experienced a drop in their resting heart rate, indicating better cardiovascular health. Some people forget that their heart is a muscle. If you keep it beating at a constant rate, then it doesn’t have to work harder, and therefore it isn’t getting any stronger. This can be a problem for people who regularly stick to the elliptical or treadmill and never reach at least 80% of their max heart rate.

Overall, there is not a big difference in the number of calories burned between HIIT and steady-state cardio, but HIIT may have some additional anaerobic and cardiovascular health benefits. Deciding whether to do HIIT versus MISS can also depend on a variety of other factors. For example, your diet. If you are on a low carb diet, or are carb cycling, you may want to do a MISS workout on low carb days rather than a HIIT workout because HIIT requires a lot of carbohydrate (glucose and glycogen), whereas MISS primarily uses lipids for energy. Also, if you are doing weightlifting in addition to cardio, MISS might be a better option because HIIT offers some of the same benefits as weightlifting. Another thing to consider is that HIIT is very strenuous, and it may be challenging to jump right into an advanced HIIT workout especially if you are just beginning an exercise program. That being said, if you are the type of person who prefers weightlifting and doesn’t need to incorporate as many body weight exercises into your workout regime to build muscle, then by all means, stick to weightlifting and steady state cardio. However, if you like doing HIIT workouts either because they take less time to do or because they don’t require any fancy gym equipment, that’s also fine. Whatever your personal fitness goals and workout preferences are, the most important thing is always to listen to your body and do what’s best for you.


Questions and comments:

Which do you personally prefer, HIIT or MISS?

If you previously did HIIT because you believed you were burning hundreds of calories post-workout, do you think you will still continue doing HIIT now that you know the after burn effect isn’t true?

Comment below if you’d like to share any thoughts about HIIT or if you have any questions.

Thanks for reading:)


Recommended Further Reading

Metabolic adaptations to short-term high intensity training: a little pain for a lot of gain,

Effect of Exercise Intensity, Duration and Mode on Post-Exercise Oxygen Consumption

Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max

8 Benefits of High-Intensity Interval Training (HIIT)

High-intensity interval training for health and fitness: can less be more?

Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women