The Science of HIIT: The Truth and Limitations of Short, High-Efficiency Workouts

Starting with a Student Who Had “No Time”

A few years ago, I coached an engineer who worked in the Neihu Science Park. Let’s call him A-Zhe. The first time he came to me, he said outright: “Coach, I can spare at most three sessions a week, half an hour each. Online, everyone says four minutes of HIIT equals an hour of jogging, so I want to train that way directly.”

I’ve heard that line too many times. For office workers, people who eat out, and parents in Taiwan, time is always the scarcest resource, and HIIT (High-Intensity Interval Training) just happens to be marketed as a kind of “time magic”—as if all you need to do is grit your teeth, sweat it out for four minutes, and you can bypass those boring cardio sessions that start at an hour.

I didn’t pour cold water on him, but I told him something I say to every student: HIIT is a great tool, but it’s a double-edged sword. Used correctly, it amplifies your limited time; used incorrectly, it gets you injured, overtrained, or even worse off than not training at all. In this article, I want to honestly lay out what I’ve observed on the sidelines over the years, read in the literature, and verified with my students. What’s real, what’s exaggerated, who it suits, and who should be careful—that’s what “The Science of HIIT” should really look like.

What Is HIIT? Let’s Define It Clearly First

Many people think that as long as it’s “breathless, exhausting, and has intervals,” it’s HIIT. That’s not the case. The core definition of HIIT is: short bursts of effort at an intensity near or above VO2max, or clearly above the lactate threshold, interspersed with low-intensity recovery, repeated over multiple sets.

The key here is “intensity.” True high-intensity intervals typically fall at 85% to 95% or more of maximum heart rate, with a perceived exertion (RPE, Rating of Perceived Exertion, on a 1 to 10 scale) of about 8 to 9—that is, the level where “you can only spit out two or three words at a time.” If you can still chat comfortably during the intervals, it’s probably just “moderate-intensity intervals,” not true HIIT.

I often use a simple comparison table with my students:

Training Type	Intensity (% of Max HR)	Perceived Exertion RPE	Typical Single-Session Duration	Representative Workout
LISS Low-Intensity Steady State	60–70%	3–4	40–90 minutes	Easy long rides, jogging
MICT Moderate-Intensity Continuous	70–80%	5–6	30–60 minutes	Tempo rides, aerobic cruising
Threshold/Sweet Spot Intervals	80–90%	6–7	8–20 minutes/interval	20-minute threshold segments
HIIT High-Intensity Interval Training	85–95%+	8–9	20 seconds–5 minutes/interval	Tabata, 30/30, 4×4
SIT Sprint Interval Training	All-out sprint	10	10–30 seconds/interval	6–8 all-out sprints

The SIT (Sprint Interval Training) at the bottom of the table is actually an extreme cousin of HIIT, with higher intensity and shorter duration. The “four-minute Tabata” that’s all over the internet falls roughly between HIIT and SIT. Understanding these distinctions matters because their physiological effects, recovery demands, and risk levels are all different.

Physiological Adaptations: What HIIT Actually Does Inside Your Body

To understand why HIIT is “efficient,” you first need to look at which physiological systems it stimulates. I’ll explain it in terms coaches can understand, without piling on intimidating jargon.

1. Central Adaptations: Building Up the “Pump”

When you repeatedly approach VO2max, your heart must pump out large volumes of blood in a short time. The ventricles stretch during the filling phase, and myocardial contractility improves. Over the long term, the volume of blood pumped per beat (stroke volume) increases. This means your resting heart rate drops, and your heart works more efficiently at the same intensity. This is the core engine of endurance performance and HIIT’s strongest adaptation.

2. Peripheral Adaptations: An Efficiency Revolution at the Muscle Level

At the muscle level, HIIT stimulates an increase in the number and quality of mitochondria (the factories in cells that convert oxygen into energy), greater capillary density, and an improvement in what’s called metabolic “buffering capacity”—in plain terms, your muscles become more resistant to acidity and better at handling the metabolic waste that accumulates during high-intensity exercise. That’s also why, after a few weeks of HIIT, you feel like “on the same hill, my legs don’t give out as quickly.”

I often use an analogy with my students to explain the difference between central and peripheral: The heart is the engine; the muscle mitochondria and capillaries are the transmission and drivetrain. No matter how big the engine is, if the drivetrain is inefficient, the power won’t reach the wheels; conversely, no matter how smooth the drivetrain, if the engine output is insufficient, you won’t be fast. The beauty of HIIT is that it applies pressure to both ends at once—a single high-quality interval session forces the heart to pump hard while also forcing the muscles to work in an oxygen-deprived, highly acidic environment. This “dual stimulus” is one source of its time efficiency.

3. Neural and Movement Economy: An Often Overlooked Piece

There’s one adaptation few people talk about, but I think is especially important for cycling or running: movement economy. Under high intensity, your nervous system is forced to recruit muscle fibers and coordinate force production more efficiently. Over time, at the same speed or power output, the energy you need to expend decreases. That’s why some people don’t improve much in VO2max but their actual performance clearly gets better—they’re running or riding “in a more economical way.” This aspect isn’t easily captured by a single metric, but it genuinely affects how your riding feels.

4. Metabolic Adaptations and the Mythologized “Afterburn Effect”

Here I need to specifically discuss EPOC (Excess Post-exercise Oxygen Consumption), commonly known as the “afterburn effect.” It refers to the period after exercise when the body continues to consume oxygen and burn calories at an elevated rate to replenish energy stores and clear metabolic byproducts.

Empirically, HIIT’s EPOC is indeed higher than moderate-intensity continuous exercise of the same duration. According to one study, EPOC after HIIT is about 66 kcal, while moderate-intensity continuous training is about 53 kcal, with the difference concentrated mainly in the first 10 minutes after exercise, and HIIT also shows a higher rate of fat oxidation afterward (see references at the end). Another study shows HIIT’s EPOC is about 319 ml of oxygen, clearly higher than moderate-intensity continuous’s roughly 168 ml.

But please note the numbers I’m using—the difference between the two is on the order of “a few dozen kcal,” not the astronomical “burning hundreds more calories” of marketing hype. A tea egg is about 70 kcal, and a bowl of braised pork rice easily exceeds 500 kcal. So if you think HIIT’s afterburn effect can offset a serving of fried chicken, that’s a misunderstanding. EPOC is real, but it’s a supporting player, not the lead.

I often remind my students of a logical flaw that’s easy to overlook: Because HIIT is short in duration, the total calories it burns “during the workout itself” are often actually fewer than an hour of easy riding. Even adding in those few dozen kcal of afterburn, HIIT doesn’t necessarily win in total energy expenditure. So if your primary goal is purely “burning calories,” don’t assume HIIT is always the most efficient choice—its real value lies in “getting cardiovascular adaptations in less time,” not “burning more calories in less time.” Once you separate these two things, your expectations of HIIT become much more realistic.

HIIT vs. Traditional Cardio: What the Evidence Says

This is the question I get asked most: “Coach, should I do HIIT or just ride/run slowly?”

The answer is more complex than the marketing slogans. Let me organize the more reliable current evidence into a few key points:

Improving VO2max: It Depends on Who You Are

Multiple systematic reviews and meta-analyses show that in the general healthy population, the difference in VO2max improvement between HIIT and MICT (moderate-intensity continuous training) is often smaller than expected, and in some studies, it is not even statistically significant. In other words, for a healthy young person who already exercises regularly with sufficient weekly volume, HIIT is not necessarily “better” at improving maximal oxygen uptake than traditional aerobic training.

However, in clinical or at-risk populations (e.g., cardiovascular disease patients, coronary artery disease patients, cancer survivors), HIIT demonstrates an advantage over MICT in improving cardiorespiratory fitness (VO2peak). For example, in meta-analyses of coronary artery disease patients, both HIIT and MICT significantly improved oxygen uptake, but HIIT provided an additional improvement of about 2 mL/kg/min (see references at the end).

This contrast is interesting and important: HIIT’s relative advantage is more pronounced in individuals with poorer cardiorespiratory fitness and greater room for improvement. This also matches my observations on the sidelines—the thinner your foundation, the easier it is to “pick up” noticeable gains from high-intensity stimuli; whereas seasoned veterans often need more sophisticated training plans to squeeze out further progress.

Time Efficiency: HIIT’s True Home Turf

If the question changes to “achieving similar cardiorespiratory benefits with less ‘training time,’” then HIIT’s advantage becomes much clearer. The literature generally supports that short-interval, low-volume, short-duration HIIT is a time-efficient strategy for developing VO2max. For someone like A-Zhe, who only has three 30-minute sessions per week, this is exactly why HIIT exists—not because it’s “more powerful,” but because “when you only have a little time, it can squeeze out more.”

I’ve organized the trade-offs between the two approaches into a decision table:

Aspect	HIIT / SIT	Traditional Aerobic MICT / LISS
Time required per session	Short (15–30 min incl. warm-up)	Long (40–90 min)
Cardiorespiratory improvement (general population)	Good, but not necessarily superior to aerobic	Good
Cardiorespiratory improvement (low baseline/patients)	Clear relative advantage	Good
Caloric expenditure per session	Moderate (short duration)	High (long duration)
Fat oxidation/afterburn	Slightly higher afterburn	Higher fat utilization during exercise
Recovery demands	High (needs 48+ hours)	Low (can be done daily)
Injury/cardiovascular risk	Higher, requires screening	Lower
Psychological burden/boredom	Short but very painful	Long but relatively easy
Suitable for base building/mileage accumulation	Not suitable	Very suitable

Once you understand this table, you’ll see why I never let my athletes “only do HIIT.” The ideal configuration is almost always a mixed model of aerobic base building + a small amount of high-intensity work, not an either/or choice. This is also the spirit of “polarized training” that has been used in endurance sports for years—most time easy, a little time very hard, and the gray zone in between gets the least attention.

Practical Methods: HIIT Workouts You Can Follow Directly

Enough science—here’s something you can use immediately. The following three workouts suit different purposes, and I’ve set them primarily in the context of “indoor trainer cycling” or “safe outdoor routes,” because for most people in Taiwan, these are easier to execute than track sprints and put less stress on the knees.

Workout A: Beginner Intro (30/30 Intervals)

Suitable for those just starting from the couch and wanting a gentle introduction to high intensity.

• Warm-up: Easy ride/run for 10 minutes, RPE 3–4
• Main set: 30 seconds hard (RPE 8) / 90 seconds recovery (RPE 3), repeat 6–8 times
• Cool-down: Easy ride for 5–8 minutes
• Total duration: ~25–30 minutes, 1–2 times per week

Workout B: Advanced Classic (4×4 Norwegian)

This is a widely studied workout with strong cardiorespiratory benefits, suitable for those with several months of regular exercise experience.

• Warm-up: 10 minutes progressing to RPE 6
• Main set: 4 minutes hard (RPE 8–9, ~90% max HR) / 3 minutes active recovery (RPE 4), repeat 4 times
• Cool-down: 8 minutes
• Total duration: ~45 minutes, 1–2 times per week (at least 48 hours between sessions)

Workout C: Very Short Sprints (SIT, Advanced and Healthy Individuals Only)

This is the closest to the “four-minute myth” prototype, but the intensity is extremely high and the cardiovascular load is significant. Anyone with cardiovascular risk factors should get medical clearance before attempting this.

• Warm-up: Must be thorough, at least 10–12 minutes
• Main set: All-out sprint 20–30 seconds (RPE 10) / full recovery 3–4 minutes, repeat 4–6 times
• Cool-down: 10 minutes
• Total duration: ~25–30 minutes, at most 1–2 times per week

I’ve also put together a “dosage table” for how to distribute these workouts across the week—this is what most people are missing: not how to do one session, but how many times per week and how to pair it with aerobic work:

Level	High-intensity sessions per week	Aerobic sessions per week	High-intensity share of total volume	Recommended intervals per session
Beginner (0–3 months)	1	2–3	~10–15%	6–8 short intervals
Intermediate (3–12 months)	2	3–4	~15–20%	4×4 or 8–10 intervals
Advanced (1+ year)	2–3	4–5	~20% cap	Periodized

Please note the principle in the rightmost column: high-intensity training should generally not exceed 20% of total training volume. This is where I’ve seen too many people crash—they turn every session into HIIT, thinking the more painful the better, and then three weeks later they catch a cold or get knee pain, and blame it on “maybe I’m not cut out for exercise.” It’s not that you’re not suited for it—the dosage was wrong.

Common Mistakes and Fixes: The Pitfalls I Keep Seeing in My Athletes

Mistake 1: Turning Every Session into HIIT

This is the number one killer. HIIT’s effectiveness comes from “high-intensity stimulus + adequate recovery.” Without sufficient recovery, you’re just chronically digging yourself into a hole. Fix: Strictly adhere to the “high-intensity no more than 20% of total volume” principle, and spend the rest of your time on easy aerobic work. Even if it feels so easy you wonder “is this even working?”—it is. That’s how base building works.

Mistake 2: Rushing the Warm-up

High-intensity intervals place sudden heavy loads on the cardiovascular system and tendons. Going straight into sprints with a cold body is a high-risk scenario for strains, cramps, and even cardiac events. Taiwan’s damp, cold winter mornings make this especially important. Fix: Warm up for at least 10 minutes before HIIT, and gradually raise your heart rate so your body “knows what’s coming.”

Mistake 3: Confusing Intensity—Treating Moderate as High

Many people think they’re doing HIIT, but their work intervals aren’t hard enough and their recovery intervals aren’t easy enough—so they get stuck in the “gray zone,” exhausted but getting the worst of both worlds. Fix: Use heart rate or power as objective measures. If you don’t have these devices, use the “talk test”—during hard intervals you should only be able to spit out two or three words; during recovery, you should be able to catch your breath and speak full sentences.

Mistake 4: Neglecting Recovery and Sleep

Training is just the “stimulus”; real progress happens during recovery. In Taiwan’s overtime culture, many people train hard but are severely sleep-deprived—it’s like placing orders constantly but never shipping. Fix: Treat sleep as part of your training plan. The day after a HIIT session, schedule easy work or rest—don’t stack another hard session on top.

Mistake 5: Ignoring Nutrition and Hydration, Especially in Taiwan’s Summer

Taiwan’s summers are hot and humid, and both indoor and outdoor HIIT cause heavy sweating and electrolyte loss. Add to that the often imbalanced carb-to-protein ratio of eating out, and recovery quality suffers. Fix: Replenish fluids, adequate carbs, and protein before and after exercise; avoid scheduling extreme workouts like SIT during hot outdoor hours (e.g., summer afternoons)—move them to early morning or evening, and watch for signs of heat illness.

Mistake Six: Progressing Too Fast, Being Too Greedy

Many people, once they taste success, want to “up the ante”—this week 4 sets worked, so next week let’s do 8, and the week after, train every day. The body adapts at its own pace; rushing things usually results in injury and stagnation. Correction: Follow the principle of “change only one variable at a time.” If you want to increase volume this week, don’t simultaneously increase intensity. Give each new load at least two to three weeks to adapt, and observe your body’s response before deciding the next step.

I often tell my athletes: “Progress doesn’t come from how hard you train in a single session, but from accumulating weeks and months of training without injury or interruption.” A moderate training plan you can sustain long-term will almost always beat an extreme plan fueled by a three-minute burst of enthusiasm. This is also why I place the words “dose” and “recovery” ahead of “intensity.”

Applicability and Contraindications: Who Should Train, Who Should Be Cautious

This is the section I most want to make clear, because it concerns safety.

HIIT is particularly suitable for:

• Healthy office workers with limited time who want to improve cardiorespiratory efficiency
• Endurance athletes with an aerobic base who want to break through a plateau
• Specific patients undergoing cardiac rehabilitation under the supervision of a professional medical team (in recent years, the acceptance of supervised HIIT in cardiac rehab has increased, but it must be under the premise of “supervised and assessed”)

The following groups must first seek medical evaluation or train under professional supervision—do not start on your own:

• Those with known or suspected heart disease, a history of chest tightness or chest pain, or unexplained fainting
• Hypertensive patients with poorly controlled blood pressure
• Diabetics (especially those with unstable blood sugar control, neuropathy, or retinopathy; high intensity may carry additional risks and requires individualized assessment)
• Those who have been sedentary for years, are older, or have multiple cardiovascular risk factors (family history, smoking, high cholesterol, obesity, etc.)
• During pregnancy, early postpartum, or any state of acute infection or inflammation

In Taiwan, we actually have a relatively accessible healthcare environment through the National Health Insurance. If you fall into the above categories, getting a basic cardiac evaluation (such as an exercise ECG, as determined by your physician) before starting high-intensity training is not difficult, and this “insurance” is well worth it. I would rather you spend an extra clinic visit than have to handle a preventable accident on the sidelines.

A simple self-screening logic: if you experience unusual chest tightness, chest pain, abnormal breathlessness, dizziness, or palpitations even during low-intensity exercise, stop and seek medical attention. Don’t face it with a “just push through it” mentality—this isn’t a matter of willpower; it’s a matter of safety.

Actionable Advice for Readers at Different Levels

If You Are a Complete Beginner

Don’t rush into HIIT. Spend 4 to 6 weeks building the habit of “moving regularly”—three times a week, 30 minutes of easy-to-moderate cycling or brisk walking is fine. Once your body adapts to the regular load, start with the 30/30 from Workout A, just once a week. Remember: what you lack isn’t intensity; it’s a foundation and a habit.

If You Are an Athlete with a Base

You are best suited for a hybrid model of “aerobic base building + 1–2 HIIT sessions per week.” You can use the 4×4 from Workout B as your main session, paired with easy long rides/runs to accumulate mileage. The key is to keep high-intensity work within 20% of total volume and take recovery seriously. If progress stalls, the first things to check are usually not “insufficient intensity” but problems with “sleep, nutrition, or total volume planning.”

If You Are a Seasoned Endurance Athlete

What you need is periodization—not cramming high intensity into every week, but adjusting the type (VO2max intervals, threshold, sprints) and proportion of high-intensity work based on how close your target race is. At this stage, HIIT is a precise scalpel, not a sledgehammer to swing every day.

For seasoned athletes, I usually provide a simplified four-phase periodization framework to help everyone understand that “even with HIIT, it should look different in different phases”:

Periodization Phase	Primary Goal	HIIT Type & Proportion	Aerobic Proportion	Notes
Base Phase	Accumulate mileage, build aerobic foundation	Minimal, primarily threshold intervals	High (80%+)	Lay the groundwork; don’t rush to go hard
Build Phase	Raise VO2max	4×4, primarily long intervals	Moderate-high	The period with the most noticeable progress
Specific Phase	Mimic race demands	Race-pace, sprint mix	Moderate	Simulate race conditions
Taper Phase	Pre-race recovery, maintain freshness	Very minimal, short and sharp	Low volume, high quality	Don’t push hard here

The key takeaway from this table is: HIIT isn’t a “fixed formula”; it’s a set of tools adjusted according to your goals. For the same person, the intervals done in the base phase and the specific phase should differ in intensity, duration, and proportion. Once you understand this, you’ve moved beyond the beginner mindset of “doing the same few sets every week.”

If You Belong to an At-Risk Group

Your first step isn’t finding a training plan; it’s finding a physician. After obtaining an evaluation and clearance, prioritize supervised, progressive programs. Make moderate-intensity continuous training your main focus, and introduce high intensity sparingly and conservatively under professional guidance.

A Case Study Throughout This Article: What Happened to A-Zhe

Back to A-Zhe from the beginning. I didn’t have him start with SIT. Instead, we spent four weeks building regularity, then introduced Workout A, and only two months later moved to 4×4. Six months in, his resting heart rate had dropped noticeably, and he could climb the familiar hill near his home without having to stop and catch his breath—all of this with just about three hours per week.

There was actually an episode worth mentioning along the way. In the third week of introducing 4×4, A-Zhe texted me after a session saying, “Why am I so tired this week? My legs feel like lead,” and asked if he should grit his teeth and add more training to “break through” it. I asked him not to add anything; instead, I had him cut the second high-intensity session of that week and replace it with an easy ride. I also asked about his sleep—sure enough, he had been working on a project deadline and had only slept five hours a night for several days. After the adjustment, his condition was back the following week. I particularly wanted to share this episode because it demonstrates a key judgment call: when you feel “unusually tired,” the correct response is usually not to add more, but to step back and examine your recovery. Not being able to distinguish between “push” and “pull back” is the root cause of many people getting stuck or injured.

He later said something to me that I find more fitting than any data: “So HIIT isn’t about using less effort; it’s about spending my limited effort in the right places.”

That is the core message I want to convey through this article: HIIT is not a time magic trick; it’s a powerful tool that demands respect and proper dosing. It is genuinely effective, especially when your time is limited or your cardiorespiratory foundation has significant room for improvement. But it also has clear limitations and risks, and it shouldn’t be glorified as a “four minutes replaces one hour” miracle cure. By honestly understanding its truths and limitations, you can truly benefit from it—rather than getting hurt.

FAQ

Q: Can HIIT really replace jogging or long rides?
A: Not completely. The systems stimulated and the adaptations elicited by the two overlap but are also complementary. The best approach is to combine them, not choose one over the other. The value of building an aerobic base is something HIIT cannot replace.

Q: How many times a week is best for HIIT?
A: For most people, 1–2 sessions per week is sufficient. Advanced athletes can do up to 2–3, but they must pair it with adequate aerobic work and recovery, and keep high-intensity volume below 20% of total training load.

Q: Is HIIT the most effective for fat loss?
A: The afterburn effect is real but limited in magnitude (on the order of tens of kilocalories). Fat loss success primarily depends on overall energy balance and diet. Exercise is a supporting factor, not the main driver—don’t pin all your hopes on the afterburn.

Q: How do I control intensity without a heart rate monitor?
A: Use the “talk test” and RPE. During high-intensity intervals, you should only be able to utter two or three words; during recovery, you can speak in full sentences. This is more practical than blindly chasing numbers.

Q: Is it normal to feel very sore and tired the day after HIIT?
A: Moderate soreness is normal. However, if you experience several consecutive days of extreme fatigue, low mood, declining performance, or even an unexplained rise in resting heart rate, poor sleep, or loss of interest in training, these could be signs of insufficient recovery or overtraining. You should proactively reduce volume and review your sleep and nutrition. If necessary, schedule a full deload week to let your body recharge. This isn’t laziness—it’s part of smart training.

Q: Can HIIT be done on an indoor trainer? Will the results be compromised?
A: Absolutely. In fact, given Taiwan’s weather (too hot in summer, damp and cold in winter, and frequent rain), an indoor trainer is the most stable environment for performing HIIT. It allows precise power control without interference from traffic lights or road conditions, making it easier to hit your target intensity. The only thing to watch out for is poor heat dissipation indoors—be sure to use a fan and stay well hydrated.

Q: Is fasted HIIT better for fat loss?
A: This is a common myth. Fasted high-intensity exercise not only tends to impair performance but can also pose risks for those with unstable blood sugar control. For the vast majority of people, having some simple carbohydrates before HIIT (e.g., a banana) helps maintain intensity and improves the quality of the session. The key to fat loss remains overall diet, not whether a particular session is done fasted.

Q: Is HIIT still suitable for older adults (e.g., 50s, 60s)?
A: Age itself is not a contraindication; what matters is health status and gradual progression. Many older adults can safely benefit from moderate interval training with proper assessment and guidance. However, because cardiovascular risk rises with age, medical evaluation before starting becomes even more important, and intensity should be introduced more conservatively and gradually.

Conclusion

Over years of coaching athletes, my attitude toward HIIT has remained consistent: respect its power, and acknowledge its limits. It can multiply your time when you’re busy, but it can also bite back when you let your guard down. Keep intensity at the appropriate proportion, treat recovery as part of training, and put safety before efficiency—this is how you make HIIT work for you over the long term.

I hope this article lets you see a more complete, more honest picture of HIIT beyond the myth of the four-minute sweat session. Train smart, and train for the long haul.

Finally, if you take away only one sentence from this article, I hope it’s this: Intensity determines whether you improve, recovery determines whether you can sustain it, and safety determines whether you can stay in the game at all. All three are indispensable, and the order cannot be reversed. As you pursue efficiency, always treat your body as a long-term partner, not a resource you can endlessly overdraw. See you out there.

---

This article is for educational purposes and does not replace individual diagnosis or treatment advice from a physician, physical therapist, or nutritionist. If you have cardiovascular disease, diabetes, hypertension, or any other chronic condition or physical discomfort, please consult a qualified medical professional before starting high-intensity training.

References

• The Effect of Exercise Training Intensity on VO2max in Healthy Adults: An Overview of Systematic Reviews and Meta-Analyses — https://pmc.ncbi.nlm.nih.gov/articles/PMC11022784/
• Effects of different protocols of high intensity interval training for VO2max improvements in adults: A meta-analysis of randomised controlled trials — https://pubmed.ncbi.nlm.nih.gov/30733142/
• Effects of High-Intensity Interval vs. Moderate-Intensity Continuous Training on Cardiac Rehabilitation in Patients With Cardiovascular Disease: A Systematic Review and Meta-Analysis — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8904881/
• Acute interval running induces greater excess post-exercise oxygen consumption and lipid oxidation than isocaloric continuous running in men with obesity — https://www.nature.com/articles/s41598-024-59893-9
• Isocaloric High-Intensity Interval and Circuit Training Increases Excess Post-Exercise Oxygen Consumption and Lipid Oxidation Compared to Moderate-Intensity Continuous Training — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12567725/

Related Reading

• Exercise Intensity and Health Benefits: Is High Intensity Really Better? A Coach’s Guide to the HIIT vs. Moderate-Intensity Trade-off
• High-Intensity Interval Training (HIIT) on the Bike: The Science of Improving Cardiorespiratory Efficiency in a Short Time
• The Scientific Application of HIIT in Running
• Weekly Frequency of High-Intensity Intervals (HIIT): How Many Sessions Per Week Are Effective Without Overtraining