# How high is too high? Your running and heart rate questions answered

With most GPS watches now offering heart rate data as standard, it's never been easier to get insights into how hard your heart is working on the run. But do we really understand the science behind the statistics? RW caught up with leading sports cardiologist Dr Dan Augustine to get answers to some of the most frequently asked questions about running and heart rate.

## Why does heart rate increase during exercise?

'With any intensity of exercise, the body needs more oxygenated blood to get into your vital organs. And the way the heart does that is it increases its cardiac output – which is your heart rate times the amount of blood your heart pumps with each beat. At rest, that’s usually somewhere between 3-5 litres per minute. During exercise, it can significantly increase – some elite athletes get as high as 14 litres per minute.'

## What effect does age and gender have on heart rate?

'The average female resting heart rate is slightly higher than the average male resting heart rate. The average male is around 70ish beats per minute; the average female is a couple of beats per minute higher. That’s largely driven by the difference in size between men and women: female hearts are slightly smaller so they beat a bit quicker to get to the required cardiac output.'

## What effect does age have on heart rate?

'When you’re an adult, the resting rate doesn’t vary much with age. What varies is your peak heart rate. There are few ways to try to calculate your peak heart rate, some more accurate than others. The equation '220 minus your age' was first written about in the 1970s and not intended to be applied strictly, as it has faults. In younger people, it probably overestimates what your peak heart rate should be. In older people, it probably underestimates what your peak heart rate should be.

As a general rule of thumb, as we get older our peak heart rate drops. If you’re 40, your peak heart rate should be around 180. By the time you’re 90, that will reduce to around 140. There is a slight difference in men and women when it comes to the dropping of peak heart rate with age: the rate of decline of peak heart rate is slightly slower in women.'

## What is a healthy heart rate while exercising?

'That’s a really tough question to answer. Heart rate will vary across age and gender, as discussed. It will also vary with fitness. If you’re just starting out, you’ll find your heart rate is much higher than if you’re four months into a training programme. What I’d recommend is that if you’re new to exercise, take a broader view of your own health.

Do you have high blood pressure? Are you a smoker? Is there a family history of heart disease? Then when you start exercising, use a perceived exertion score and try to marry that up with your heart rate. So if your heart rate is shooting up but you’re not feeling like you’re doing a lot, then that might be worth looking into. Be mindful of your exercise history and what you’re trying to achieve – and don’t push yourself too hard too soon.'

## Is it safe for your heart rate to be above 200bpm while exercising?

'I don’t see many people who present with peak heart rates in the 200s, but if you’re otherwise healthy, you’ll probably be OK, so long as it's in the 200s for only a short amount of time. Some US studies, for example, found that people in their 40s when running on a treadmill can achieve a peak heart rate of 190, which is higher than some people might assume [at that age].

When you exercise, your heart tries to make workflow more efficient. And there’s only so high your heart rate will go before it loses that efficiency. What you’ll find is that if you’re a seasoned endurance runner, over time your peak heart rate will be less, because your heart adjusts physiologically to the amount of exercise you’re doing. So if you’re exercising aerobically 3-4 hours a week for months, the heart will start to adapt.

The way it adapts is that the cardiac output has to increase to give the body more blood. That means more blood is leaving the heart, which, in turn, must mean that more blood must is returning to the heart. And that’s when the heart starts to become bigger. This is what is called ‘Athlete’s Heart’. If the heart is bigger, the amount of blood it pumps per beat is bigger too, so your heart rate doesn’t have to be as high to get to the required cardiac output. That’s why your heart rate lowers the fitter you get, and you can get recreational runners with heart rates in the 40s.'

## Is it safe to push yourself really hard during exercise?

'The overall message here is, doing exercise is much better than not doing exercise. If we could put the benefits of exercise into a pill, it would be better than anything I could prescribe to patient in terms of Type 2 diabetes prevention, blood pressure, bone density, etc.

It comes back to what your baseline fitness is. If you’re healthy with no risk factors, you’re going to be fine to exercise. If you have cardiac disease, you can also benefit greatly from exercise, but it probably requires a more measured and tailored approach. You might consider seeing a specialist before you decide to start an exercise schedule.

For the majority of people who have no risk factors and are already healthy, though, pushing themselves to high intensity will be fine. Things go wrong when you don’t have that background training, or you don’t factor in outside factors such as hot weather conditions. Having said all that, European guidelines would suggest that healthy adults who are doing 3-4 hours of aerobic exercise a week have a cardiac sports screen once every two years.'

Dr Dan Augustine is a sports cardiologist: screenmyheart.co.uk

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