Wise Up, “Boring” Cardio Is Better than HIIT in Most Ways
HIIT is not it. If you're like most people, it shouldn't be your choice of cardio. It under-delivers on many aspects; learn more in this article.
HIIT sucks. If you’re like most people, it shouldn’t be your choice of cardio.
I’ll tell you why.
For context, HIIT has built up a reputation for being a superior cardio form because of its time efficiency.
Supposedly, for every, say, 30 minutes you spend on MISS and/or LISS, you could have achieved the same — if not better — outcomes with HIIT in half that time:
- Calorie burn and, in turn, weight loss
- Health improvements (specifically, cardiometabolic benefits and mortality)
- Fitness improvements
1️⃣ Interval training: Split into sprint interval training (SIT) and high-intensity interval training (HIIT).
2️⃣ Steady-state training: Split into low-intensity steady-state (LISS) and moderate-intensity steady-state (MISS).
| Type | % of HR max |
|---|---|
| SIT | > 85% (maximal effort) |
| HIIT | ≥ 85% |
| MISS | 70% to 84% |
| LISS | 50% to 69% |
But now, research says that’s grossly overblown or completely wrong.
HIIT isn’t any better for weight loss
HIIT and steady-state training resulted in similar fat and weight loss, according to this 2021 systematic review.
Why? Because HIIT doesn’t burn more calories than steady-state cardio. In fact, it may burn fewer.
🔍 Let’s look at the numbers.
During the session
Most HIIT sessions feature a 1:1 work-to-rest ratio.
I.e., in a 20-minute session, you’d only be “actively working out” for 10 minutes.
So, given a MET value of 11.0 for HIIT (vigorous effort), a 25-year-old woman who’s 170 cm and weighs 65 kg would burn ~163.4 calories from the 20-minute HIIT session.
Compare that to what she’d burn from a 20-minute, moderately-paced jog (MET value = 9.0): ~245.1 calories.
Objection — what if we compared the same work duration?
Or, in other words, what if her HIIT session lasted 40 minutes instead, with 20 minutes of “work” and 20 minutes of rest?
Well, yes. Her calorie burn would then have been 326.8 calories, which is greater than that from a 20-minute, moderately-paced jog. But an extended HIIT session poses 2 problems:
- Unrealistic: You’re supposed to push yourself, and hard, during HIIT workouts. Unless you’re a top-tier athlete, consistently hitting ≥ 85% of your HR max during a prolonged HIIT session will be a huge, if not impossible, ask.
- Against the basic principle of HIIT workouts: HIIT workouts are meant to be short and sweet.
🧑⚖️ Objection, overruled.
After the session
A unique advantage interval training has over steady-state cardio is excess post-exercise oxygen consumption (EPOC).
Since the body has to produce energy anaerobically during HIIT (and SIT), it racks up an “oxygen debt” that it must clear. To do so, it increases its oxygen uptake post-exercise, resulting in an elevated metabolic rate.
What’s the increase? An estimated 6% to 15% of the exercise’s total energy expenditure.
Going back to our 20-minute HIIT session example, this means our girl could have burned up to 187.9 calories (math: 1.15 x 163.4 calories) in total from her workout.
That’s still fewer than she’d have burned from a 20-minute, moderately-paced jog.
📌 A 2023 meta-analysis ranked cardio as the least effective among 10 weight loss protocols. The most effective was a combination of calorie restriction, a high-protein diet, and exercise.
🔗 Get a better understanding of the relationship between cardio and weight loss here.
HIIT doesn’t make you any healthier
Research suggests HIIT doesn’t result in better health outcomes than steady-state training.
Mortality
According to a 2022 analysis, adults who perform 2 to 4 times the recommended amount of vigorous (150 to 299 minutes weekly) or moderate physical activity (300 to 599 minutes weekly) showed 2% to 4% and 3% to 13% lower mortality, respectively.
Higher levels of physical activity beyond those amounts did not clearly show further lower all-cause mortality.
Glucose control
In individuals with both normal and impaired glucose, this 2022 systematic review found that:
- “There were no differences in glucose or insulin AUC (area under curve) between HIIT and moderate-intensity continuous training (i.e., MISS) intervention arms.”
- “Both HIIT and MICT (i.e., MISS) are effective for reducing postprandial glycemia and insulinemia.”
Cardiometabolic risk factors
Here’s what a 2015 study said:
- “Participation in HIIT or moderate-intensity training (MIT) displayed improved insulin sensitivity, reduced blood lipids, decreased body fat percentage, and improved cardiovascular fitness.”
- “... a relatively short duration of either HIIT or MIT may improve cardiometabolic risk factors … with no clear advantage between these 2 specific regimes.”
HIIT isn’t any better at preserving muscle mass
Because HIIT more closely resembles resistance training, it’s often said that it could minimize the interference effect (compared to steady-state cardio).
But a 2016 study says the opposite.
More specifically, it was found that HIIT diminished resistance-training-induced muscle mass increases more than steady-state cardio — although, admittedly, the magnitude of between-group differences was small.
Why? It comes down to recovery costs.
True HIIT asks you to go almost as hard as you can for (usually) 30 seconds, and that’s very, very taxing.
It’s a zero-sum game.
When your body has to recover from that, it’ll divert resources from what would have been meant to repair and build your muscles.
Gene Lim
HIIT isn’t easy to stick to
Dynamic. Fun. Exciting.
Since you constantly switch between exercises, HIIT is supposedly more enjoyable and tolerable than the monotonous, continuous slog on a treadmill or Stairmaster.
Surprise, surprise.
Here’s what a 2023 study had to say:
- “Compared to moderate-intensity exercise, more individuals assigned to HIIT did not adhere to their prescription when unsupervised, most likely because they could not.”
- “Some dropped out, whereas many of those who continued exercising did so at lower-than-prescribed levels of intensity.”
Once again, it’s worth remembering that HIIT is intense (it’s in the name, after all).
Meaning?
It’s unlikely to be pleasant for most, except the minority who take a masochistic delight in extremely tough workouts.
When does it make sense to do HIIT?
To be clear, I’m not saying HIIT is “bad” or “useless”.
It can make sense for certain people, including those who are:
- After a specific physiological adaptation: The principle of specificity states that how you train should mimic the movements, actions, and skills required to perform and excel in the game, activity, or event you’re participating in. E.g., if you’d like to compete in a HYROX race, HIIT deserves a spot in your training regimen.
- Preferential to HIIT: In a time crunch? Bored to tears by long, continuous cardio sessions? If your choice is either doing HIIT or not doing cardio at all, then, of course, go for HIIT.
Bottom line? HIIT is not the holy grail
Neither is it suitable for everyone.
💬 So, before you do HIIT, have an honest conversation with yourself:
- What am I hoping to achieve from HIIT?
- Do I enjoy HIIT?
- Is preserving and/or building muscle mass my priority?
