HRV vs. VO2 max vs. ECG: Which wearable metric ACTUALLY matters? | Prof. Malcolm Findlay

**Jonathan Wolf** (0:00)
Welcome to ZOE Science and Nutrition, where world leading scientists explain how their research can improve your health.
The use of wearable devices that promise to transform our health is booming. But do they work? These watches and rings provide measurements and feedback to help you understand your health and take steps to improve it. Measurements include sleep quality, step count, and others. But the metric getting a lot of attention right now is heart rate variability, or HRV. And it's no wonder. HRV is said to be a good indicator of your stress levels, of your heart health, and your overall well-being. But is it really all that useful to track HRV? Is there anything else that would be better off tracking instead? And how accurate are these wearable devices anyway? Joining us with answers is Professor Malcolm Findlay, a board certified cardiologist and electrophysiologist, and an honorary professor of cardiovascular medicine and devices. A leader in the field of measuring heart health, he's well positioned to give us the truth. You'll leave today's episode understanding whether a wearable device could help you, how to get the most out of it if you have one, and what are the best things to track to improve your health. Malcolm, thank you so much for joining me today.

**Malcolm Findlay** (1:35)
Thank you so much. Thanks for having me.

**Jonathan Wolf** (1:37)
It's a pleasure. Now, we have a tradition here at ZOE where we always start with a quick fire round of questions from our listeners, and you can answer with a yes or a no, or if you have to, a one-sentence answer. Okay. Can HRV tell you something about the health of your heart?

**Malcolm Findlay** (1:54)
Yes.

**Jonathan Wolf** (1:55)
Can wearable health tech help you look after your heart?

**Malcolm Findlay** (1:58)
I think so.

**Jonathan Wolf** (2:00)
Could focusing on the wrong numbers put your heart at risk?

**Malcolm Findlay** (2:04)
I think if you focus on the wrong numbers, you can do the wrong things and get the wrong idea. So I guess yes.

**Jonathan Wolf** (2:10)
Can two people with the same heart rate have completely different HRVs?

**Malcolm Findlay** (2:14)
Oh yeah, absolutely.

**Jonathan Wolf** (2:16)
If you want to live longer, is HRV the number to focus on?

**Malcolm Findlay** (2:21)
If you want to live longer, there are lots of things to focus on, and HRV is just one of the many things that you might use to guide you, but actually I think there are more sensible things you could use to guide you on focusing on HRV.

**Jonathan Wolf** (2:34)
And what's the most common myth that you hear about heart health?

**Malcolm Findlay** (2:38)
Okay, so the most common myth is that one thing, for example, concentrating on doing exercise, can negate concentrating on some really important medical issues, such as high cholesterol. And so just looking after yourself in a general way doesn't negate the need for some proper medical intervention.

**Jonathan Wolf** (2:58)
Well, I'm excited to get into all of that, Malcolm. And actually for today's show, I woke up this morning, I thought I'm going to actually wear two different types of watch, both of which tell my heart rate. I thought it would be quite fun to do that as we go through this. And they also tell me my heart rate variability, this HRV thing that you mentioned, which I know is hugely popular at the moment. What is HRV?

**Malcolm Findlay** (3:24)
Heart rate variability is something you can measure from the heart rate. Like the technical side of things is it measures the subtle changes in the beat to beat time differences of each heartbeat.
When we talk about HRV with watchers and so on, it's not really the big changes that the heart rate will change when doing exercise or when you get excited about something or going to sleep at night. It's more like the subtle wobbles in the heart rate from beat to beat and looking at the course of that over several minutes or even over the whole day. So the measure is quite a mathematically complex measure that was first brought out in the 1970s, I think, as a way of guiding medical treatment and risk prediction. I think in hard core medicine, it didn't fulfill its promise in that people were trying to look for heart rate variability as a good predictor for future disease or future problems. But actually, it's kind of a weak one compared to some other very serious medical testing that we have, for example, CT scans or MRI scans. But as a wearable device, I think wearables have picked up on this measure because you can take that and it gives another insight about your overall physical general health and general health metrics.