Hacker News Reader

Comment by RubyRidgeRandy | Hacker News Reader

What has been well understood for quite some time is that low, steady-state cardio will burn the most calories over high-intensity workload. The effort needed to maintain a high-intensity workload is exponential. The average non-trained person may be able to walk 20-30 miles at one time before their legs give out, that same person wouldn't be able to sprint a mile, let alone half a mile if we're talking all-out sprint. Even if you take into account increased VO2 max it doesn't add up. High-intensity exercise has its place in health, but is a poor tool for weight loss.

Dr. Mike Israetel had a video on this exact topic https://www.youtube.com/watch?v=_0ejGgLRQZI

View on HN

The post described the mechanism; it's not about the calories directly burned by the activity, but rather the effect on appetite. You lose weight by eating less, and hard exercise can make it easier to do so.

I think its a bit more complex than that. HIIT directly burns less calories, but it creates more muscles over time. Similar in weightlifting if you go for low reps high weight workouts which are basically HIIT.

In both cases, your metabolism adjusts - it feeds more muscles, its set into high-energy mode with 'fast' digestion.

I wouldn't recommend it to most though - if done properly its very taxing. I mean being in anaerobic state and pushing through is a hard sell to people who barely muster enough motivation to do occasional jog or spinning. One needs to be in top shape overall for it, no hidden heart issues etc.

I think people need both steady state and HIIT. Much like it's hard to go super heavy low reps all the time when lifting. It's good to cycle up and down.

As you mention, HIIT is also very hard for many people do even if they are healthy and want to do it. The body naturally fights going all out.

I've pitched training BJJ on HN (well to anyone really), and HIIT is yet another reason. People who train end up doing HIIT without even realizing. The body is in defense mode which breaks down some of the natural steady guardrails.

> wouldn't be able to sprint a mile, let alone half a mile if we're talking all-out sprint

Can anyone? Almost by definition, your top sprinting speed, e.g. what you would use for 100m race, is going to be different than your speed running a mile, even if you are an olympic athlete.

If you run like you would for a 100m race you wouldn't even be able to complete a 400m race.

The difference is the amount of time required. Time spent being equal, you will get more fat burn/weight loss through HIIT exercise

That's true, but people tend to misunderstand this.

Of course sprinting all-out for 5 minutes is better than walking for 5 minutes. If all you have is 5 minutes, and you're trying to get the most out of that session without any other consideration, you should sprint.

But for most people, 5 minutes of all-out sprinting is very, very hard, and has a very fatiguing effect - you won't want to (or be able to) exercise again for a while. As opposed to walking, which most people can realistically do for a long time.

The concept here is the amount of fatigue you're accumulating. As a fat-loss tool, a low-fatigue exercise that you can do for a long time will mean much more total calories burned, as opposed to a high-fatigue exercise you'll only realistically do for a very short duration.

This reminds me: Scott Adams said the optimal exercise routine is the one that maximizes your chances of exercising again the next day. A good way of thinking about it.

What about a ladder workout? We did these in track and field and it was a brutal burn that would send people puking by the fence by the end and not being able to walk up stairs for a few days after. You'd run a 100m, short rest, 200m, rest, 300m, rest, 400m, rest, 300m, rest, 200m, rest, 100m, then you are simply cooked. Two weeks of this though and you are whipped back into shape for track season.

I don't have exact figures, but the amount of calories burned in very strenuous activity is about 3 times "light" activity like walking (I think - would love a legit reference though!)

So let's say you do the ladder routine. I don't have any idea how fast people typically sprint, but let's take 2 minutes per sprint - we have 100 twice, 200 twice, 300 twice, and 400, for a total of 7 sprints - so we'll say 14 minutes (and I think I'm exaggerating up?) In terms of calories burned, this is the "same" as a 45 minute walk.

I assume, by the way you describe it (people can't walk up stairs for a few days, people puking) that this is very hard on people. They're probably not doing this every day.

As opposed to walking 45 minutes, which is incredibly easy and won't make anyone feel bad, and you can definitely do every day.

Of course, I'm only talking calories burned here - for health and for improving conditioning, of course you need something more strenuous!

> but is a poor tool for weight loss

Still better than nothing and you only need up to 20 min to complete training.

Reply on news.ycombinator.com