HIIT Vs Steady State Cardio – Which is better for you?

We drank till late last night. 

I know that’s not the best way to start a fitness article.

But it’s true. As is the fact that the topic of this post came up during said revelry.

Emblematic of our generation, we drank single malt (with only ice and water — lowest calorie drink that keeps you hydrated too), ate healthy (baked, high-protein bars, low carb) home-made snacks, and discussed our fitness regimes (some existing, others intended).

We discussed weight-training and yoga and trekking and running. Carefully examining the benefits of each, we discussed how each played a distinct role in a holistic fitness routine. We even tackled complex questions around power output and cadence and VO2 max.

But just as we were beginning to feel pleased about our mental mastery of all things physical (a pursuit that I believe is the biggest impediment to achieving fitness), someone asked a really simple question:

What is even the point of cardio?

For a few seconds, that question hung like a dark cloud over an otherwise fairly energetic and involved (and inebriated) conversation.

And rightly so. Because it isn’t as simple a question as it seems. Here’s what the questioner was really asking:

What’s even the point of a 20–30min steady-state cardio workout in the gym if it won’t help me burn fat fast? And when the calories burned are so low that just a banana shake right after would neutralize the benefits?

Shouldn’t I just do HIIT instead?

I’m sure you’ve heard of HIIT — High-Intensity Interval Training. One of the longest-standing trends in the ‘quick fat loss’ space. Every celebrity trainer worth his salt has his own version of HIIT. Tabata, Insanity, Johnson & Johnson— you name it.

So what my friend was asking was: Why should I bore myself to death running at 9kmph on a treadmill for 30mins, to barely burn 250 Kcal — when I can do the same in a 15 min HIIT workout and arguably burn a lot more weight or fat?

• Aerobic Vs Anaerobic Exercise: Ok, let’s hold that thought and get some basics out of the way first.

• Max Heart Rate (MHR): Your MHR = 220 minus Your Age = the heart rate you shouldn’t exceed if you want a good chance of staying alive.

• VO2 Max: is the measurement of the maximum amount of oxygen a person can utilize during intense exercise. It’s a great way to measure aerobic endurance and cardiovascular fitness. More on this later.

• Steady State Cardio: This is any cardio where your heart rate remains between 65%–80% of your MHR for a long period of time. Running or Cycling for 20-30 mins in the gym is a perfect example.

HIIT: Is any exercise where, in recurring intervals, your Heart Rate spikes to 80%+ of MHR. So you reach the 160+ zone, stay in it for a minute, then rest to bring it down, and then go at it again. 

As you’d guess from the definition, HIIT is brutal. Our hearts don’t like to be made to operate near MHR. Neither do our muscles.

Why? Well, some more basics:

• Aerobic exercises: Muscles need oxygen. Any exercise where they get enough of it during the workout is called aerobic. Jogging, swimming, and cycling are good examples.

• Anaerobic exercises: You’re demanding so much work off your muscles, and your heart’s beating so fast to keep up, that there just isn’t enough oxygen available during that intense period of exercise. So the muscles need to shift to anaerobic, or non-oxygen-requiring, sources of energy to sustain. 

That’s HIIT. That’s also strength training and 100m sprints. 

Fun Fact 1

Ever felt that burn after a short intense burst of exercise? Or in the last few reps of a strength workout?

That’s lactic acid, building up in your muscles. Why? Because in the absence of adequate oxygen, your body makes this lactate that can be consumed for energy even without oxygen. 

But the body can’t do this for too long. 1–3 mins at max.

Hence that is the limit of High-Intensity exercise bouts. And this lactate can build up in your bloodstream faster than you can burn it off. This is why the burning sensation sometimes continues even after you’ve kept the weights down.

HIIT: Pros and Cons

As brutal as it sounds (and it is), HIIT has a ton of benefits:

Fat Burn

That’s the first benefit of HIIT that all believers will throw at you. And with it, they’ll throw the word afterburn — or the calories you keep burning even after you’re done with your workout. 

Now there is some truth to that. Your heartbeat remains elevated for a long time after you’ve finished a HIIT workout. And some studies (not all) do seem to suggest that while you might’ve burnt lesser calories during the actual workout, you burn more during the entire day if you’re on HIIT.

But the science isn’t conclusive. And like all other fads, those who have a financial motive to push HIIT (hint: check if they are also selling you a HIIT program), tend to massively exaggerate this afterburn effect. 

Time Efficient

That, HIIT is. Workouts are faster. You burn ~70% calories in half the time it’d take you with Steady State (SS) cardio. And then you burn about 30%-40% more during the day. So overall, it’s a good deal.

Metabolic Flexibility

HIIT forces you to switch repeatedly between aerobic and anaerobic energy consumption, and the more you do it, the better your system gets at it. Over time, this can make your body more adept at burning fat for fuel. Which is awesome.

So, overall, HIIT helps you burn fat fast. And the metabolic flexibility improves what athletes call explosive strength, or the ability to quickly deliver a burst of energy and move fast. 

Fun Fact 2

Ever noticed how marathoners are these lean, almost anemic beings. While sprinters (like Bolt) are all big and muscular. Ever wondered why? Read this post about Training Legs, to find out.

Coming back to HIIT though- as you’d imagine, this extreme form of work, has downsides too:

Overtraining

Too much HIIT, over a long period of time, can break your system. 

Continuously shifting between such peaks and troughs of heart activity can leave you in a constant state of anxiety and stress. If you want to know what I mean, do a late-night HIIT workout and then try to sleep, even 4 hours after.

So if you’re going to do HIIT, I’d suggest you do it not more than 2–3 times a week. And preferably in the morning. Or at least 6–7 hours before you intend to sleep. 

Not for Beginners

If you’re just starting on your cardiovascular fitness journey, I’d strongly advise against HIIT. (I’d also suggest you read this article that answers the Top 5 questions that all gym beginners need to know)

You might feel it’s pushing you, and you might sweat and pant a lot, but the chances that you’ll hurt yourself are very very high. And the damage might not be outwardly visible.

HIIT can be brutal for your heart and your metabolic system. So these systems need some training before you put them to the test. Or in more technical terms, they need some Aerobic Prowess, before you put them through that Anaerobic hell. 

They first need Cardio.

SS Cardio: Pros and Cons

Remember that HIIT is a relatively new fad. For a long time before that, people have been losing weight through plain-old cardio. And plain-old cardio isn’t just for plain-old weight loss. It has a host of other benefits:

Cardiovascular Health

Remember VO2 max, the max oxygen your body is able to utilize during a workout. It’s when the body reaches its VO2 Max, that it switches to anaerobic fuel. On which it can’t last very long. 

So it’s clear, if you can increase your VO2 max, you can increase your endurance and perform at higher levels, for longer. 

And guess which form of exercise improves oxygen-carrying capacity? Well, the one that actually uses oxygen. 

I can’t overstate the importance of this one simple benefit. As your body becomes better at carrying and consuming oxygen, a host of changes start occurring.

You’d recall from primary biology, blood’s job is to carry oxygen to the cells so they can live. As this delivery system becomes more efficient, the heart needs to pump lesser per minute. So your Resting Heart Rate (RHR) starts decreasing. 

And lower RHR, leads to lower anxiety, lower stress, better ability to focus, better ability to recover from stress — the list is endless. 

Cons

The biggest allegations leveled against SS Cardio are that it’s boring and that the repetitive stress on a few body parts (knees, joints) can cause them long-term harm.

It’s Boring

I can write a whole new post about why ‘boring’ is precisely the reason why you need to do steady-state. 

The mental benefits that things like long-distance running provide — the fortitude, the discipline, the ability to keep enduring pain and yet keep moving — far, far outweigh the already enormous physical benefits. 

Life is repetitive and cyclical and boring. So please, plug in some music, put on your running shoes, find flow in the repetition, and just do it. 

It Harms

The jury might be out on really long-distance, steady-state, high-impact sports like full marathons. But it’s pretty clear that running 5kms on a treadmill isn’t going to do anything bad to your knees. In fact, some studies suggest, it might make them stronger.

So what should I do?

Both. 

But do cardio first. 

Measure your RHR. If it is >65 BPM, I’d suggest you stay away from HIIT.

First, do a few months of steady-state, and get to a stage where you can do medium intensity work for about 30–40 mins. By this time, your RHR should come below 65. That’s when I’d suggest you introduce some HIIT into the mix.

Beyond that point, a mixture of the two is the best strategy. 

1. Steady State will keep pushing up your system’s Aerobic capacity. So it’ll take progressively more work to make you enter the Anaerobic state.

2. When you do enter it, your HIIT training will help you juice that much better.

3. Afterward, once you’re back in the aerobic zone, your cardio training will help you recover faster. So you can again push yourself. 

Now that is a virtuous fitness cycle if there ever was one.