A few weeks ago I wrote about a study that highlighted a number of significant changes on the cellular level produced by high intensity interval training. If you take that study on its own, HIIT sounds like the best thing to hit the exercise world since the invention of sneakers. Of course we know that any given study can only look at a few very specific parameters and you have to take the results in context with a much larger body of study.
The results were so intriguing from the first study I reviewed that I couldn’t help but start to ask an assortment of questions about HIIT training. What is the best combination of work and rest intervals and what differences exists when using different interval/rest times? What differences then exists between different types of intervals: running, biking, rowing, weight lifting, body weight exercises and so on? How do different populations (men vs. women, young vs. old, sedentary vs. active, endurance athletes vs. strength athletes) react to different types of interval training? What are the differences between interval training and other forms of training (traditional strength training, endurance training, etc.)? How does interval training impact individuals with various medical conditions such as diabetes and obesity and how are those impacts different then other forms of exercise?
So here we go with the first of what will probably be many follow up articles about various aspects of high intensity interval training.
Steady-state and moderate intensity intervals can be just as good as HIIT in untrained individuals
Let’s begin by going way back to 2015 and a study by Foster et al. (2015) in the Journal of Sports Science and Medicine. Relatively inactive young adults were put into either a steady-state training group, a very high intensity-brief interval protocol (Tabata) or a moderate intensity –moderate time interval (Meyer). The steady state group cycled for 20 minutes at a moderate to vigorous intensity. The Tabata group cycled for 20 seconds of intense work then 10 seconds of unloaded cycling for 8 sets, equaling a total of 4 minutes. The Meyer interval group did 20 minutes of cycling consisting of 13 sets of 30 second work intervals followed by 60 seconds of active recovery. Each group performed three workouts per week for 8 weeks, totaling 24 exercise sessions.
All three groups showed significant improvement in measures of aerobic and anerobic capacity however, there were no significant differences between the groups, suggesting that in relatively inactive young adults it doesn’t really matter which approach is used. All three groups did increase the intensity at which they worked out over the course of the study and even the steady-state group was cycling at a fair degree of difficulty but overall, this study does not support the increased value of high intensity work for this population.
Usually most research studies are more concerned with the physiological impact of whatever they are testing but in this study the authors did start to take into account a factor that really comes into play in the real world, the psychological motivation of exercisers. How much they really enjoy a particular form of exercise and how likely they are to actually do it. We can come up with the world’s greatest form of exercise but if it is so miserable to do only a tiny number of people will actually perform it and for the majority of people who need to exercise, the approach is worthless because they won’t do it.
In this study, subjects’ enjoyment of all three forms of exercise went down over time but significantly more so for the Tabata group. While many people may find a moderate intensity interval approach more interesting than a steady state approach, the very high intensity intervals may just be too much for many members of the general public, especially those who have been more sedentary. Yes high performing individuals may need the stimulus of very high intensity intervals to elicit improvements but for the majority of people it is probably not that crucial. And ultimately we need people to want to continue to participate in exercise over time to truly gain the benefits and if their level of enjoyment is so low due to the discomfort of very high intensity intervals they are much more likely to stop exercising and not enjoy any of the benefits.
This also carries over to the time benefits of HIIT. While a HITT workout can be completed in a reduced period of time, if by the time participants feel recovered enough to go on with their day they have needed as long as participants who engaged in longer duration more moderate to vigorous exercise sessions then there is no net benefit to the shorter duration period of exercise. In this study the Tabata group needed so long to recover they didn’t see any time saving benefit as compared to the other two groups. Keep in mind the Tabata subjects were exercising at a very high intensity.
So there you go, if you are working with or are someone newer to exercise you do have to put some real effort into what you are doing but you don’t have to go all out with extremely high intensity intervals to elicit many of the same benefits. At least until you read HITT Reverses Aging At a Cellular Level. I’ve got a nagging feeling that despite the important observations about participant behavior in this study, we are going to find a lot of data in future articles that continues to support higher intensity intervals.
HIIT improves body composition, strength, aerobic capacity and quality of life in overweight women
Now that we’ve taken a peak at young sedentary subjects let’s see what impacts HIIT has on a population of women with a little more to love. Sperlich et al. (2017) studied women ages 18-35 who had body mass indexes (BMI) of 25 or higher, categorizing them as overweight, who had not been exercising for the previous six months or longer. What is most interesting about this study is that instead of building intervals around traditional cardiovascular exercises, the authors developed interval circuits consisting of body weight exercises such as burpees, push-ups, lunges, squats and sprints. The intervals used look far more like the type of HIIT circuits that are being used by personal trainers and group exercise instructors in classes at gyms and training facilities.
The subjects were broken down into two groups. One group (HITT) performed three interval workouts per week for 9 weeks while the other group (Combined) performed the same workout twice a week and one low-intensity higher-volume cardiovascular workout consisting of jogging and walking. The authors theorized the participants in the Combined group would experience some different cardio-respiratory and metabolic changes along with higher perceptions of quality of life.
Subjects in both groups saw similar decreases in weight, BMI, waist-to-hip ratio and fat mass while also seeing similar increases in fat-free mass (=muscle). Ratings of perceived exertion for both groups went down over time in a similar manner. Cardio-respiratory measures were all similar with the exception of peak oxygen uptake which was improved to a greater extent I the HIIT group.
Strength and related performance measures which consisted of push-ups, burpees, one-legged squats, timed skipping and counter-movement jump height all improved for both groups with no differences between groups. The HIIT group did see a higher increase in the number of leg levers they could perform.
For all quality of life measurements both groups showed similar results with the exception of the HIIT group reporting higher perceptions of pain while the Combined group reported enhanced perceptions of general health.
So, if you are more concerned with getting the most possible improvement in VO2max in this population you should do 3 HIIT workouts but if you are more concerned with participants’ perceptions of general health and less discomfort you might want to lean towards a combined approach that replaces one HITT workout with some jogging and walking. Either way, both approaches appear to be very beneficial for overweight women (at least under 35) and it’s safe to say this study supports body weight resistance exercise based high intensity intervals.
Polarized training vs HIIT vs threshold vs high volume training in elite endurance athletes
Up to now we have mostly looked at the effect of HIIT on less experienced or untrained individuals. While the results there are positive with HIIT there are arguments for other forms of training. When it comes to very experienced individuals and elite athletes all previous claims are off. Their bodies are already highly adapted to training and under a tremendous amount of stress. How they respond to certain stimulus can be totally different then untrained individuals.
Stoggl and Sperlich (2014) attempted to answer some of the questions regarding different training approaches for elite endurance athletes. They began with the concept that endurance athletes use some combination of four training approaches. The first and most common is the more traditional high-volume training (HVT) done at a lower intensity that is usually less than 80% of max heart rate, 65-75% of peak oxygen uptake (VO2peak) and at lower blood lactate levels. The second approach is training at or near the blood lactate threshold (THR). The third approach is HIIT training and the fourth is polarized training (POL) that uses some combination of the other three approaches.
Utilizing international level competitors in cycling, triathlon, running and cross country skiing the authors had the subjects train for 9 weeks under one of the four conditions. They attempted to design workout protocols that resembled what these athletes would actually do for their normal training. Five key performance variables were measures: VO2peak, velocity/power output at the lactate threshold (V/Plt), work economy, peak running velocity or power output (V/Ppeak) and time to exhaustion (TTE).
Their first interesting finding was that the only training approach that resulted in subjects losing a significant amount of weight was HIIT. This is despite the HIIT group having less volume in their training then the other three groups. While elite endurance athletes often are trying not to lose any additional body mass when they are in need of manipulating their body composition we can see that HIIT may be a useful training approach.
When it came to VO2peak the polarized group far and away had the greatest gain at 11.7% followed by HITT at 4.8%. Work economy improved the most following HIIT while work economy expressed as a percentage of VO2peak improved only following polarized training.
The greatest improvement in time to exhaustion was found in the polarized group, almost double the next best approach, HIIT. Peak velocity and power improved the most with polarized training followed closely by HIIT. Both significantly better than the other two approaches. Velocity/power output at lactate threshold also showed the greatest gains with polarized training again followed by HIIT.
Clearly in this population of highly trained athletes a combined training approach that includes HIIT showed the greatest improvements in performance variables that generally equate to success in ones sport. So while we might argue for a higher percentage of HIIT in the less trained individual and someone who’s primary objective is weight loss, for more elite athletes we can see HIIT is important for performance improvement but needs to be integrated with other training techniques. There seems to be a multiplying effect in results when HIIT is integrated with other techniques.
So there you go. Three distinctly different groups, inexperienced younger adult males, overweight adult females and elite endurance athletes. All three can benefit in some meaningful way from HIIT but we need to balance the unique demands and psychology of each group. While elite athletes can handle the high intensity aspect of HIIT, for other groups it may be wise to utilize some work done at more moderate intensities to make the exercise more enjoyable and increase the likelihood of someone sticking around long enough to make significant changes. We also saw that with our non-endurance athlete groups that interval circuits made up of body weight exercises seem to produce meaningful results.
Works Cited:
Foster, C., Farland, C., Guidotti, F., Harbin, M., Robers, B., Schuette, J., Tuuri, A., Doberstein, S. and Porcari, J. (2015) The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. Journal of Sports Science and Medicine. 14: 747-755.
Sperlich, B., Wallmann-Sperlich, B., Zinner, C., Von Stauffenberg, V., Losert, H., Holmberg, H. (2017) Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women. Frontiers in Physiology. Apr 3;8:172
Stoggl, T. and Sperlich, B. (2014) Polarized training has greater impact on key endurance variables than threshold, high intensity or high volume training. Frontiers in Physiology. Feb 4;5:33
