Dr. Andy Galpin

In fact, you've probably done it before.

It doesn't have to be that extreme.

You could use shorter durations, say two minutes, three minutes.

Four minutes is a very, very common one you'll find in research.

So four minutes of all-out exercise, four minutes of recovery.

Repeat it again two to four times.

What's critical to understand here is these work when you're actually achieving a maximum in that time domain.

So you can't do four minutes at 70%, rest for four minutes, and do that again.

That's going to burn you some calories and has other benefits of just making you feel better today and some other stuff like that.

But in terms of VO2 max, that's probably not the most efficient thing you can do.

So to summarize all of that stuff, spend a good amount of time at a lower intensity.

That's going to drive efficiency, a common adaptation there since it's going to be the highest activity you can do to maximize utilizing fat for fuel.

You're still going to be burning primarily carbohydrates.

Don't get that confused.

But that's the best way to burn some fat.

So this is typically associated with higher metabolic efficiency.

getting better at using fat as a fuel source and things like that.

It's also easy to recover from.

It's not going to change your autonomic nervous system that much.

So you typically don't see big drops in HRV scores.