Most of us learned at a young age that promises of “more for less” are usually a sham.
This is particularly true when we’re talking fat loss.
All we have to do, we’re told by shady supplement companies, is pop their pills and powders and we’ll be shredded in no time?
No amount of supplements can get you the body you want. In fact, most supplements can’t even help you get the body you want–they’re just completely worthless.
All we have to do, we’re told by shady exercise “gurus,” is spend a couple hours per week doing their workout routines and we’ll look like a Greek statue?
Getting into great shape may not be as complicated as many people think, but it requires that you get a lot of “little” things right ranging from caloric intake to macronutrient balance to progressive overload to training frequency and more.
“7 Minute Workouts” and fad dieting ain’t gonna cut it.
Now, if you’ve already heard of high-intensity interval training (also known as HIIT), you’ve probably heard a similar story: that it has near magical fat burning powers.
That you can do just a few minutes per day and watch fat melt off your body.
HIIT isn’t the alpha and omega of fat loss…but it can be a powerful weight loss tool when you know how to use it properly.
And that’s what we’re going to talk about in this article:
- What high-intensity interval training is (and what it isn’t).
- Why it’s great for fat loss.
- Why it’s superior to low-intensity steady-state cardio for optimizing body composition.
- How to do it right.
By the end, you’re going to know how to get the absolute most fat-burning bang for your sweaty buck.
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- What Is High-Intensity Interval Training (and What Isn't)?
- High-Intensity Interval Training and Burning Fat
- High-Intensity Interval Training and Your Muscles
- How to Create an Effective High-Intensity Interval Training Routine
- What About Supplements?
- My Personal HIIT, Weightlifting, and Supplementation Routines
- The Bottom Line on High-Intensity Interval Training
Table of Contents
High-intensity interval training, or HIIT for short, is a style of exercising where you alternate between periods of (almost) all-out and low effort.
Hence, the name.
The high-intensity intervals push your body toward its metabolic limits (basically as hard as you can go) and the low-intensity intervals allow it to recover (catching your breath).
You probably already knew that, though, and have several specific questions, such as…
- How “intense” do the high-intensity intervals need to be? How hard should you push yourself and how long should you go for?
- How do the rest periods work, exactly?
- How long should your HIIT workouts be?
- How frequently should you do them?
Basically…how do you get the most out of individual HIIT workouts and out of your regimen as a whole?
Well, let’s find out.
Use this workout and flexible dieting program to lose up to 10 pounds of fat and build muscle in just 30 days…without starving yourself or living in the gym.
How Intense Your High-Intensity Intervals Should Be
When you review scientific research on high-intensity interval training, you’ll see a lot of talk about something called VO2 max.
Your body’s VO2 max is a measurement of the maximum volume of oxygen that it can use, and it’s a major factor in determining your endurance level.
Its relevance to HIIT is this:
Studies show that you need to reach between 80 and 100% of your VO2max during your high-intensity intervals to reap the majority of HIIT’s benefits.
That’s nice to know but not very practical because it’s hard to approximate your VO2 max while exercising. There just aren’t reliable enough indicators to guess with any accuracy.
Fortunately, you can also work with a more useful metric: Vmax.
Simply stated, you’ve reached a Vmax level of exertion when you feel you can’t bring in as much air as your body wants (if you can comfortably hold a conversation, you’re not there).
For most people, this is about 90% of all-out effort.
1. Your goal during your high-intensity periods is to reach and sustain your Vmax.
That is, you need to get moving fast and long enough to make your breathing labored, and you need to hold that speed for a fair amount of time.
As you can imagine, this means hard work. Think sprinting, not jogging.
2. Your goal during your HIIT workouts is to repeatedly achieve and sustain this Vmax level of exertion.
This might seem obvious, but it bears attention because the total amount of time you spend at the Vmax level of exertion determines the overall effectiveness of the HIIT workout.
That is, a “HIIT” workout that racks up maybe a minute of movement at Vmax level is going to be far less effective than one that accumulates several minutes.
Fortunately, this is just a matter of programming your workouts properly and not being a wuss when you do them.
We’ll talk about the workout programming soon and whenever you’re feeling wussy, here’s a friendly kick in the ass. 🙂
So, that’s “HIIT 101.”
Let’s now take a closer look at why we should choose it over easier, less stressful forms of cardio.
Most cardio machines have pretty graphs that recommend you keep your heart range in middling “fat burning zone.”
If you do this, it’s claimed, you’ll maximize the amount of fat your body burns while you exercise as opposed to sugars.
Well, there’s a kernel of truth here.
You do burn both fat and carbs when you exercise, and the proportions vary with the intensity of exercise.
That is, as exercise gets more intense, the proportion of energy coming from glycogen stores becomes much larger than that coming from fat.
This is why a very low-intensity activity like walking taps mainly into fat stores, whereas high-intensity sprints pull much more heavily from carbohydrate (glycogen) stores.
These are the main reasons why many people think low-intensity steady-state cardio is best for losing weight.
Specifically, they show that that shorter, high-intensity cardio sessions result in greater fat loss over time than longer, low-intensity sessions.
Well, let’s start with the obvious: total calories burned while exercising.
High-intensity exercise can burn quite a bit more calories than low-intensity exercise, and as fat loss is dictated by energy balance, the advantage here is clear.
Let’s say you jog several times per week and burn about 200 calories per session, with about 100 coming from fat stores.
When combined with a proper calorie deficit, those workouts will help you get leaner faster.
Better, though, would be high-intensity workouts of equal duration that burn, let’s say, 400 calories per session, with 150 coming from fat stores.
Diet notwithstanding, the workouts that burn the most energy are going to result in the most fat loss.
Energy expenditure while exercising alone doesn’t fully explain how just better high-intensity interval training is for losing fat, though.
A study conducted by The University of Western Ontario gives us insight into how much more effective it really is.
Researchers had 10 men and 10 women train 3 times per week, with one group doing 4 to 6 30-second treadmill sprints (with 4 to 6 minutes of rest in between each), and the other group doing 30 to 60 minutes of steady-state cardio (running on the treadmill at the “magical fat loss zone” of 65% VO2 max).
After 6 weeks of training, the subjects doing the intervals had lost more fat.
Yes, doing 4 to 6 30-second sprints burns more fat than 60 minutes of incline treadmill walking.
The exact mechanisms behind HIIT’s superiority aren’t fully understood yet, but scientists have isolated quite a few of the factors:
- Increased resting metabolic rate for upward of 24 hours after exercise.
- Improved insulin sensitivity in the muscles.
- Higher levels of fat oxidation in the muscles.
- Significant spikes in growth hormone levels (which aid in fat loss) and catecholamine levels (which are chemicals your body produces to mobilize fat stores for burning).
- Post-exercise appetite suppression.
- And more…
The science is clear: if your goal is to burn as much fat in as little time as possible, then HIIT is the way to go.
In most weightlifter’s minds, cardio and building muscle are pretty much antithetical.
You can have one or the other.
Again, there’s some truth to this, but it’s an over-simplification.
For example, research has shown that combining both strength and endurance training (concurrent training) can hinder your strength and muscle gains when compared to just strength training alone.
Studies have also shown that the longer your cardio sessions are, the more they impair strength and muscle growth.
That doesn’t mean that cardio directly impairs muscle growth, though. Because it doesn’t.
The right amount of cardio, however, can actually accelerate muscle growth for reasons outlined here.
What is the right amount, then?
Well, there are two factors to consider:
- The duration of the individual cardio sessions.
- The total amount of cardio done each week.
And when the goal is optimizing body composition (which requires progress in the weight room), you need to keep your individual cardio sessions short and your total weekly duration relatively low.
Only HIIT allows you to fulfill these criteria and burn significant amounts of fat.
So, chances are you’re ready for some HIIT in your life.
Well, there are five things you should consider when building a HIIT routine:
- The type of cardio.
- The length of the workouts.
- The frequency of the workouts.
- The duration and intensity of the high-intensity intervals.
- The duration and intensity of the low-intensity intervals.
Let’s look at each point separately.
The Best Types of HIIT Cardio
HIIT principles can be applied to any type of cardio but some forms are more practical (and effective) than others.
Generally speaking, the three best choices are…
The reason I recommend these three forms over others is research shows that the type of cardio you do has a significant effect on your ability to gain strength and size through weightlifting.
The long story short is this:
The more a cardio exercise mimics the movement used in muscle-building movements, like the squat or barbell row, for instance, the less it hinders strength and muscle growth.
This makes sense because one of the important parts of building strength is simply training a movement pattern repetitively. (The more you do a movement, the better you get at it.)
That said, if you can’t or don’t like to bike, row, or sprint, don’t be “afraid” of other forms of cardio such as swimming, jump roping, calisthenics, boxing, and so forth. They’re not going to whittle your muscle away.
Again, the big cardio mistake is simply doing too much.
How Intense Should Your Your High-Intensity Intervals Be?
The goal of HIIT is to go fast and hard, not slow and hard.
That means that if you’re using a machine like a bike or rower, you want enough resistance to pedal or pull against but not so much that it becomes a resistance training exercise.
That’s why the primary difference between high- and low-intensity intervals should be your speed, not the amount of resistance used.
That is, you should increase and decrease resistance but not nearly as much as you increase and decrease your speed.
Now, as you know, the key factor that determines the effectiveness of a HIIT workout is the total minutes spent at a Vmax level of exertion.
If you spend too little time at this level, it’s a quasi-HIIT workout, and if you spend too much, you’ll burn yourself out.
Well, you achieve maximum time at Vmax by, when sprinting, going for that level of exertion as quickly as possible.
Don’t “build up to it.” Give each sprint everything you’ve got right out of the gate.
In terms of duration of high-intensity intervals, 50 to 60% of Tmax is sufficient if your goal is losing fat and improving metabolic health.
Tmax is simply the amount of time you can move at your Vmax speed before having to stop.
For example, I can bike at Vmax for about 3 minutes before my heart feels like it’s going to explode, so my Tmax is 3 minutes.
Therefore, my high-intensity intervals should be about 90 to 120 seconds long (and yeah, that’s hard!)
For your intervals, you can either test your Vmax (all you need is a stopwatch) or if you’re new to HIIT, start with 30-second high-intensity periods.
Your HIIT workouts should get progressively tougher.
The more you do HIIT workouts, the more your Tmax is going to increase. This means the duration of your high-intensity intervals will need to increase as well if you want to keep it maximally effective.
As you can imagine, these workouts can get pretty damn intense for experienced athletes.
In three HIIT studies conducted with highly trained cyclists, high-intensity intervals were 5 minutes long (and improved their performance). In contrast, other research conducted with endurance athletes found that 2- and 1-minute intervals weren’t enough to improve performance.
How “Restful” Should Your Rest Periods Be?
There are two ways you can make your HIIT harder:
- Increase the length of the high-intensity intervals.
- Decrease the length of the rest periods.
I generally recommend you first work on increasing the length of the high-intensity intervals until they’re in the range of 50 to 60% of your Tmax. This makes sure you’re doing true HIIT workouts.
Once you’ve achieved that, where you go from there is up to you.
I think it’s sensible to work rest periods down to a 1:1 ratio with the high-intensity periods (90 seconds of high-intensity work followed by 90 seconds of rest, for example), and then slowly raise the duration of both the high- and low-intensity intervals, maintaining that 1:1 ratio.
For example, let’s say you start your HIIT training doing 30-second high-intensity intervals followed by 60-second rest intervals (1:2 ratio).
As you continue, you get an idea of your Tmax and work your high-intensity intervals up to the 50 to 60% range, which comes out to about 60 seconds. You work at this level, maintaining the 1:2 high/low ratio (120-second rest intervals).
In time, you feel you can push harder and maintain the 60-second high-intensity intervals but start reducing your rest times, starting with 90 seconds (1:1.5 ratio).
Eventually your body adapts to this and you’re able to work the rest periods down to 60 seconds (1:1 ratio), and when even this isn’t challenging enough anymore, you start increasing both the high- and low-intensity intervals toward 90 seconds.
(And so on.)
You should also know that your rest periods should be active recovery, where you keep moving, not a standstill.
Studies have shown that active, not passive, recovery is advantageous for reaching Vmax during the high-intensity periods and eliciting the adaptive response to the exercise that we’re after.
How Long Should Your HIIT Workouts Be?
One of the great things about HIIT is you get a lot out of what feels like little. There’s just no more efficient way to use cardio to drive fat loss and improve conditioning.
The big downside, however, is it can be quite stressful on the body, which means you don’t want to overdo it.
Do this, however, and you’ll be fine:
- Start your workouts with 2 to 3 minutes of low-intensity warm-up.
- Do 20 to 30 minutes of HIIT.
- Do 2 to 3 minutes of warm-down.
And you’re done.
There’s just no need to do longer HIIT workouts unless you’re focusing on improving performance, not losing fat.
If you feel you need more HIIT to lose weight efficiently, your diet is probably screwy.
How Frequently Should You Do HIIT Workouts?
The total amount of HIIT you should do per week depends on your immediate goals and what other types of exercise you’re doing.
If you’re looking to lose fat quickly, you don’t need to do more than 4 to 7 hours of exercise per week, and ideally you’d do more resistance training than cardio.
For example, my training and diet programs for both men and women prescribe just 3 to 5 hours of weightlifting and 1 to 2 hours of HIIT cardio per week.
This is how you lose fat and not muscle and maintain a healthy metabolism.
I saved this for last because, quite frankly, it’s far less important than proper diet and training.
You see, supplements don’t build great physiques–dedication to proper training and nutrition does.
Unfortunately, the workout supplement industry is plagued by pseudoscience, ridiculous hype, misleading advertising and endorsements, products full of junk ingredients, underdosing key ingredients, and many other shenanigans.
Most supplement companies produce cheap, junk products and try to dazzle you with ridiculous marketing claims, high-profile (and very expensive) endorsements, pseudo-scientific babble, fancy-sounding proprietary blends, and flashy packaging.
So, while workout supplements don’t play a vital role in building muscle and losing fat, and many are a complete waste of money…the right ones can help.
The truth of the matter is there are safe, natural substances that have been scientifically proven to deliver benefits such as increased strength, muscle endurance and growth, fat loss, and more.
As a part of my work, it’s been my job to know what these substances are, and find products with them that I can use myself and recommend to others.
Finding high-quality, effective, and fairly priced products has always been a struggle, though.
That’s why I took matters into my own hands and decided to create my own supplements. And not just another line of “me too” supplements–the exact formulations I myself have always wanted and wished others would create.
I won’t go into a whole spiel here though. If you want to learn more about my supplement line, check this out.
For the purpose of this article, let’s just quickly review the supplements that are going to help you get the most out of your HIIT and fat loss efforts in general.
As weight loss boils down to energy consumed vs. energy expended, caffeine helps you lose fat by increasing your body’s daily energy expenditure.
Part of maximizing the fat loss benefits of caffeine is preventing your body from building up too much of a tolerance, however. The best way to do this is to limit intake, of course.
Here’s what I recommend:
- Before training, supplement with 3 – 6 mg caffeine per kg of body weight. If you’re not sure of your caffeine sensitivity, start with 3 mg/kg and work up from there.
- Keep your daily. intake at or below 6 mg per kg of body weight. Don’t have 6 mg/kg before training and then drink a couple of coffees throughout the day.
- Do 1 – 2 low-caffeine days per week, and 1 no-caffeine day per week. A low day should be half your normal intake, and a no day means less than 50 mg of caffeine (you can have a cup or two of tea, but no coffee, caffeine pills, etc.).
Personally I get my caffeine from my pre-workout PULSE, which contains a dehydrated and concentrated form of caffeine (caffeine anhydrous) shown to be more effective for improving performance than what is naturally found in beverages like coffee.
PULSE also contains clinically effective dosages of 5 other ingredients scientifically proven to improve workout performance:
- Beta-Alanine. Beta-alanine is a naturally occurring amino acid that reduces exercise-induced fatigue, improves anaerobic exercise capacity, and can accelerate muscle growth.
- Citrulline Malate. Citrulline is an amino acid that improves muscle endurance, relieves muscle soreness, and improves aerobic performance.
- Betaine. Betaine is a compound found in plants like beets that improves muscle endurance, increases strength, and increases human growth hormone and insulin-like growth factor 1 production in response to acute exercise.
- Ornithine. Ornithine is an amino acid found in high amounts in dairy and meat that reduces fatigue in prolonged exercise and promotes lipid oxidation (the burning of fat for energy as opposed to carbohydrate or glycogen).
- Theanine. Theanine is an amino acid found primarily in tea that reduces the effects of mental and physical stress, increases the production of nitric oxide, which improves blood flow, and improves alertness, focus, attention, memory, mental task performance, and mood.
And what you won’t find in PULSE is equally special:
- No artificial sweeteners or flavors..
- No artificial food dyes.
- No unnecessary fillers, carbohydrate powders, or junk ingredients.
The bottom line is if you want to know what a pre-workout is supposed to feel like…if you want to experience the type of energy rush and performance boost that only clinically effective dosages of scientifically validated ingredients can deliver…then you want to try PULSE.
And for the same reasons it’s also no surprise that fat burners are some of the most expensive supplements on the shelves and feature some of the loudest marketing claims, often making big promises of “scientifically proven” rapid fat loss.
The reality is most “fat burners” are junk but there are a handful of natural, safe substances that have been scientifically proven to accelerate fat loss. And that’s why I created PHOENIX.
PHOENIX’s caffeine-free formulation is helps you burn fat faster in three different ways:
- It dramatically increases metabolic speed.
- It amplifies the power of fat-burning chemicals produced by your body.
- It increases the feeling of fullness from food.
It accomplishes this through clinically effective dosages of several ingredients, including…
- Synephrine. This increases both basal metabolic rate and lipolysis, inhibits the activity of certain fat cell receptors that prevent fat mobilization, and increases the thermic effect of food (the “energy cost” of metabolizing food).
- Naringin. This stimulates the production of a hormone called adiponectin, which is involved in the breakdown of fat cells, and that it activates a type of receptor in fat cells that regulates fat mobilization (the PPARα receptor).
Through these mechanisms, naringin also works synergistically with synephrine and hesperidin to further accelerate the basal metabolic rate.
- Hesperidin. Like naringin, this also stimulates the production of adiponectin and activates the PPARa receptor. It also improves blood flow and reduces the inflammation of blood vessels.
- Epigallocatechin gallate (EGCG). This inhibits the activity of a different enzyme also responsible for breaking down neurotransmitters that induce lipolysis. It has also been shown to reduce abdominal fat in particular.
- Forskolin. This increases blood plasma and intracellular levels of a molecule known as cAMP. When cAMP is high, it signifies a lack of ATP (the most basic form of cellular energy in the body) and thus initiates a process to make more ATP by burning through energy reserves (body fat).
- And more…
The bottom line is if you want to lose fat faster without pumping yourself full of stimulants or other potentially harmful chemicals…then you want to try PHOENIX.
Yohimbine is made from the Pausinystalia yohimbe plant, and it helps the body “tap into” fat stores.
(Not a very technical explanation, I know–if you want to know exactly how it works, check out this article of mine on how to lose stubborn fat.)
I’ve cut both with and without fasted training and yohimbine and I can say with absolutely certainty that with is noticeably faster. So much so that I think the biggest benefits of fasted training are that it lets you use yohimbine and it makes the other supplements discussed in this article more effective.
By itself, fasted training will make a slight difference in how quickly you lose fat. Combined with these supplements, however, it’s quite dramatic.
In terms of dosages, research has shown that .2 mg/kg of body weight is sufficient for fat loss purposes, and that ingesting it prior to exercise is particularly effective.
Some people get overly jittery from yohimbine, so I recommend you start with .1 mg/kg of body weight to assess tolerance. If you feel fine, then increase to the clinically effective dosage of .2 mg/kg.
Furthermore, yohimbine can raise blood pressure. If you have high blood pressure, I don’t recommend you use it.
In terms of which specific yohimbine supplement I recommend, you’re probably not surprised that I’ve included a clinically effective dosage in every serving of my pre-workout fat burner FORGE.
FORGE is a fat burner made specifically for use with fasted training and it contains clinically effective dosages of…
- HMB. β-Hydroxy β-Methylbutyrate (also known as HMB) is a substance formed when your body metabolizes the amino acid leucine.
Research shows that HMB is an extremely effective anti-catabolic agent, which means it’s very good at preventing muscle breakdown. And this means you will recover faster from your workouts and experience less muscle soreness.
- Yohimbine. Research shows that yohimbine enables your body to reduce fat stores faster, and it’s particularly useful as you get leaner and are battling with stubborn fat holdouts.
- Citicoline. CDP-choline (also known as citicoline) is a chemical that occurs naturally in the brain that increases levels of another chemical called phosphatidylcholine, which is vital for brain function.
Research shows that supplementation with CDP-choline improves attentional focus, and I included this in FORGE because most people find fasted training more mentally draining than fed training and CDP-choline can help counteract this.
The bottom line is FORGE helps you lose fat–and “stubborn” fat in particular–faster, preserve muscle, and maintain training intensity and mental sharpness.
Before I sign off, I want to quickly show you how to put these strategies together to make a powerful fat loss regimen. This is exactly what I do when I’m cutting, and it works like a charm.
If you want optimal results, you’ll lift weights 5 times per week, and do HIIT cardio 3 – 4 times per week, for about 25 minutes per session.
Here’s how training and supplementation break down:
I wake up, drink some water, and get ready to go to the gym to lift. It’s about a 15-minute drive, so before leaving, I take the following:
I then go lift for 45-60 minutes and my post-workout meal of about 40 grams of protein and 100 grams of carbohydrate is the first of the day.
My lunch is light–a salad with chicken and balsamic vinegar for dressing. The reason for this is I want my insulin levels to be at baseline by about 5:30 PM for my fasted cardio.
If I were to eat a larger lunch, like let’s say 40 grams of protein, 60 grams of carbohydrate, and 20 grams of fat, my insulin levels would likely be elevated come 5:30.
I don’t take any fat loss supplements at lunch.
Around 5:30 PM, Before Cardio
About 15 minutes before doing my fasted cardio, I take the following:
I then do 25 minutes of HIIT cardio on the recumbent bike and eat about 30 grams of protein after.
If you combine the above routine with a proper weight loss diet, you will lose fat rapidly.
If a supplement or workout or claims to be a “shortcut” for gaining muscle or losing fat, it’s likely a sham.
Well, high-intensity interval training actually delivers the goods.
It’s significantly more time effective for losing fat than traditional “low-intensity steady-state” cardio (LISS).
The bottom line is whether you want to lose fat or improve athletic performance or both, you want to include HIIT in your workout routine.
What’s your take on high-intensity interval training? Have anything else to share? Let me know in the comments below!
+ Scientific References
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- Stepto NK, Hawley JA, Dennis SC, Hopkins WG. Effects of different interval-training programs on cycling time-trial performance. Med Sci Sports Exerc. 1999;31(5):736-741. doi:10.1097/00005768-199905000-00018
- Westgarth-Taylor C, Hawley JA, Rickard S, Myburgh KH, Noakes TD, Dennis SC. Metabolic and performance adaptations to interval training in endurance-trained cyclists. Eur J Appl Physiol Occup Physiol. 1997;75(4):298-304. doi:10.1007/s004210050164
- Weston AR, Myburgh KH, Lindsay FH, Dennis SC, Noakes TD, Hawley JA. Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists. Eur J Appl Physiol Occup Physiol. 1996;75(1):7-13. doi:10.1007/s004210050119
- Lindsay FH, Hawley JA, Myburgh KH, Schomer HH, Noakes TD, Dennis SC. Improved athletic performance in highly trained cyclists after interval training. Med Sci Sports Exerc. 1996;28(11):1427-1434. doi:10.1097/00005768-199611000-00013
- Gergley JC. Comparison of two lower-body modes of endurance training on lower-body strength development while concurrently training. J strength Cond Res. 2009;23(3):979-987. doi:10.1519/JSC.0b013e3181a0629d
- Wilson JM, Marin PJ, Rhea MR, Wilson SMC, Loenneke JP, Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J strength Cond Res. 2012;26(8):2293-2307. doi:10.1519/JSC.0b013e31823a3e2d
- Boutcher SH. High-intensity intermittent exercise and fat loss. J Obes. 2011;2011. doi:10.1155/2011/868305
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- Trapp EG, Chisholm DJ, Freund J, Boutcher SH. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. Int J Obes (Lond). 2008;32(4):684-691. doi:10.1038/sj.ijo.0803781
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- Tremblay A, Simoneau JA, Bouchard C. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism. 1994;43(7):814-818. doi:10.1016/0026-0495(94)90259-3
- Van Loon LJC, Greenhaff PL, Constantin-Teodosiu D, Saris WHM, Wagenmakers AJM. The effects of increasing exercise intensity on muscle fuel utilisation in humans. J Physiol. 2001;536(1):295-304. doi:10.1111/j.1469-7793.2001.00295.x
- Scott C. Misconceptions about Aerobic and Anaerobic Energy Expenditure. J Int Soc Sports Nutr. 2005;2(2). doi:10.1186/1550-2783-2-2-32
- Billat L V. Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part I: aerobic interval training. Sport Med. 2001;31(1):13-31. http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=11219499&retmode=ref&cmd=prlinks. Accessed September 17, 2019.
- Ramos JS, Dalleck LC, Tjonna AE, Beetham KS, Coombes JS. The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis. Sports Med. 2015;45(5):679-692. doi:10.1007/s40279-015-0321-z