How Hard Should You Be Running?

How to gauge your intensity, get the most out of your workout and run harder

Sportswoman running on a road by the sea

Want to get fitter and run harder? Threshold, fartlek and hill sessions will all increase your fitness, but it can be difficult to know how you should be feeling during those harder sessions. Naturally, they will be tougher than a long, steady run, but how should the different intensities actually feel?

There are various ways of figuring this out: wearing a heart-rate monitor, listening to how your body feels and using the Rate of Perceived Exertion (RPE) Scale.


The Rate of Perceived Exertion (RPE) Scale measures intensity during aerobic and resistance exercise. It’s a tool often used by personal trainers and coaches to gauge their clients’ effort levels during sessions to make sure they are working at the right intensity. It aims to measure effort, strain, discomfort and fatigue:

1: Very light activity – hardly any exertion, but more than sleeping or watching TV.

2-3: Light activity – feels like you can maintain it for hours. Easy to breathe and talk.

4-6: Moderate activity – breathing heavily, can hold a conversation. Still comfortable, but becoming noticeably more challenging.

 7-8: Vigorous activity – borderline uncomfortable. Short of breath. Can speak a short sentence.

9: Very hard – difficult to maintain exercise intensity. Can barely breathe and only speak a few words.

10: Maximal effort – feels almost impossible to keep going. Completely out of breath. Unable to talk. Cannot maintain for more than a very short time.

It’s a useful guide to intensity, but it is open to interpretation. Running coach Nina Anderson prefers to ask clients how they are feeling. “I generally ask my athletes to run their sessions based on perception of effort, rather than on a scale of 1 to 10,” she says.


A useful tip is to block out distractions, and focus on your run. “People watch TV while on the treadmill or have their music on; I don’t do that,” says running coach Keith Anderson from Full Potential ( “I like to listen to what my body is telling me. A lot of very intelligent people are runners but they seem to stop thinking as soon as they are outside the door. Often they are just running and not thinking about it.”

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If you’re using a heart-rate monitor, you might have heard about certain target heartrate
zones. The Karvonen Formula deducts your age from 220 to provide your maximum heart rate (MHR). You then choose the desired intensity depending on the training session you are doing – so for a long steady run you’d work at 65-70% of your MHR orat 80-85% during a threshold run. But theformula is not exact. “It’s a generic way of working it out,” says Keith. “I’d take it with a pinch of salt. Wear your heart-rate monitor and create your own heart-rate history.”

Running coach George Anderson ( adds: “Heart-rate monitoring can be incredibly useful and give you a real insight but the downside is that if you start linking it to what you estimate your maximum heart rate to be, it could lead to massively under or overtraining,” he says. “A better formula is heart-rate reserve,” says Speedflex trainer Luke Copeland( “This uses 220 minus age but also takes your resting heart rate into consideration.”


The formula to calculate your heart-rate reserve is : 220 minus age minus resting heart rate multiplied by the percentage you wish to work at, then add your resting heart rate back on. For example: Confused? So are we. And even with a more accurate formula, there are other factors that can affect your resting heart rate, including getting a bug, or not being fully recovered from a previous session. So what’s the answer? “I’d recommend a mixture of heart-rate monitoring and using the RPE scale,” says Luke. “Also, nothing beats an old-fashioned talk test,” says Luke. With this in mind, let’s look at how you should feel and your ability to talk during some key sessions.

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Hills will improve the strength in your legs and make running on flat surfaces feel much easier. There are various ways of tackling hills and this will affect the intensity. “What most people think about when hill training is sprinting up to the top, throwing up and then walking back down again, and repeating until you can’t walk anymore,” says George. “Water that concept down a bit and find a hill that’s going to take you a minute to run up; it doesn’t have to be super steep. You run up that hill, and recover by jogging down. That differs from Kenyan Hills or continuous hills where you’re still working on the way down at threshold

The intensity should feel challenging, but it also depends how you structure the session. Hill sessions where you jog or walk down will give you more time to recover, which will bring the intensity down before you run up again. If you’re new to hills, you’ll work at a higher intensity than a person who already includes them in their training. You’ll probably find yourself around 8.5/9 out of 10. As you get fitter and adapt to hill training, the hills will get easier, so you’ll want to increase the number of times you run uphill, reduce the duration of the recovery intervals or find a harder hill in order to keep improving.

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Designed to get you fitter by pushing your level of controlled discomfort, running threshold means doing structured blocks of faster running followed by easier intervals to recover, and repeating for a number of times. “A training plan will progress the blocks of threshold.” says George. “Threshold is about getting your body to a point where it’s comfortably uncomfortable. You want to be able to speak two, three or four words at a time, but if you can hold a conversation then you’re not working hard enough.”Nina Anderson puts it another way: “At the end the person should feel glad to have finished but be able to have continued for a little longer if needed.”


This Swedish term means ‘speed play’ and involves running at random speeds to get you used to chopping and changing pace. This can be handy during a race when you may have to speed up or slow down suddenly on a busy course, or for a final surge of speed near the end. The intensity will vary, because your speeds will be changing randomly. “It’s all about changing the speed or intensity to suit how you feel on the run,” says Luke Copeland. “Play with the pace – anything from a 4 out of 10 when recovering all the way up to a 10 out of 10
when feeling good.”

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On the RPE Scale, aim for a 6.5/7 out of 10 and run at a conversational level. “If the purpose of the run is to improve aerobic base and increase the ‘time on your feet’ total at the end of the week, then run at a pace where conversation could be sustained throughout,” says Nina Anderson. “You need to feel as if you could have continued further. To feel tired at the end is normal, but to feel exhausted means that you’ve run too quickly.”

“A long run should be conversational and relatively comfortable,” says Keith. “The discomfort won’t be from a cardiovascular point of view, it will come from gradual onset of muscle fatigue and the sheer repetition of doing the same action.”


Keep monitoring how you’re feeling during each session. “Simple questions of self-reflection throughout can be enough to sustain the correct level of exertion,” says Nina. “For example, ‘can I maintain this rhythm for another six repetitions?’ or ‘am I working too hard?’ and ‘do I need to hold back slightly?’ Though in reality much of this comes down to experience and often means learning from mistakes made such as running too hard initially.

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