Why Your Easy Runs Suddenly Feel So Hard After 50

One of the things we see often in long runs in particular and a long, easy run, we start to see that heart rate drift.

You may be Keeping it easy.

You may be slowing down your pace and walking where you need to, but we do start to see that drift.

And it's a phenomenon called cardiac drift, right? And I want to just ask you to explain that in a little bit more detail and how to counteract that or to ensure that that's something we don't really struggle with on our long runs.

Absolutely, and it mustn't be confused with this general higher heart rate.

So it does make...

There are some subtleties in heart rate training, and this is an important one of those.

So you are thinking...

To yourself, oh my word, my heart rate's always so high.

Now when I'm doing a long run, it's like I can't control my heart rate.

And then by the end of the long run, it doesn't matter what you do.

Even when you're walking, you can't control your heart rate.

So now you feel like you're just about ready to give up.

Now that is the reality is that when we exercise, as Shona said, when we exercise for a long period of time, we get a normal phenomenon called cardiac drift.

And really that is a simple response to two things.

It is a simple response to your body needing to cool you down during exercise and particularly long-term exercise.

So what happens is that some of your blood supply gets diverted, to the periphery to help cool the body and regulate body temperature.

And some of it's obviously going to working muscles.

But that means there's a lower volume that's available for the working muscles.

So the response there is that the heart has to beat a little bit faster.

And that is subtle, but it is absolutely noticeable and it will continue to drift higher as exercise goes longer because then a second thing kicks in is that the other part of that mechanism to help to keep the body cool is that we are sweating.

And so we are losing bodily fluid.

And if we're losing bodily fluid, that means that some of the blood volume then starts to drop because we start to use some of that fluid in the blood to also go to the skin surface so that we can sweat that out and continue that cooling mechanism.

So the blood volume decreases further.

And when that blood volume then decreases further, there's another drift in cardiac and that now starts to kick in slightly late in.