Heart rate zones in exercise: what do they mean?  

You could track the intensity of your exercise by using a rate of perceived exertion (RPE). Most often this is a scale of one to ten and you decide where you’re at. If RPE one is lying in bed, ten might be being chased by an angry bull.  

The problem with using this method is that its subjective. Some people dislike or even fear pushing too hard in a workout, others would say they’re working on an RPE of two when they’re gasping for breath.  

Monitoring your heart rate keeps you honest. It’s a much more accurate way of knowing how hard you’re actually working, and seeing immediately what zone you’re in.  

Some devices, such as smartwatches, will automatically check your heart rate and give you guidance on how hard you’re working. For those who want to take this a step further, a dedicated heart rate monitor, such as the Garmin HRM Pro (a band we use regularly), will allow you to connect and share that data with other apps to build yourself a personalised training programme.  

Don’t think of your heart rate information as idle data post-workout or -if you’ve not got a heart rate monitor or fitness tracker- something you don’t need to worry about. If you can master your heart rate zones and train accordingly, then you’re well on your way to more tailored, achievable and enjoyable exercise goals. 

The first thing to do when starting on your heart rate journey is to find your max heart rate.

That way, you’ll easily know from looking at your watch, tracker, or heart rate monitor roughly how hard you’re working as many will have slightly different heart rates for the same level of effort, depending on age and fitness.  

There are several different calculations out there.

If you’re wondering which formula to use, try all three and pick a number in the middle of the range, or opt for the formula that you feel most accurately reflects your level of fitness – and, of course, if you’re doing this to start upping the level of intensity of exercise (or have any worries over your heart) it’s important to chat to a doctor first. 

Don’t worry if you’re not sure if the number you’ve settled on is right for you – once you’ve started training more regularly, you can do harder exercises (like running for a few minutes hard, jogging for the same amount of time and then repeating the first set as hard as you can… that should give you an idea of your max heart rate). 

It’s worth pointing out that none of the formulas are gender specific, and broadly speaking women have higher heart rates than men by about 5 -10 BPM. This is because women tend to have smaller hearts than men, so the muscle needs to work a bit harder to get the blood pumping around the body effectively. 

There are five different heart rate zones, reflected as a percentage of your max heart rate, and they vary from very light all the way up to maximum.

Most of us won’t exercise in that top zone very often; this is only used for very fit athletes to improve sprint capabilities or explosive power.  

Of course, if you’re planning on being the next Usain Bolt, far be it from us to stop you.

Zone 1- Very light: 50 – 60% of MHR (max heart rate) This is the zone to aim for when warming up, gradually increasing your heart rate from where it’s been at rest. It’s also used for recovery and cooldowns.  

Training in this zone encourages blood flow to the muscles. Therefore, it’s good for warm-ups, as it helps prevent injury if we start more intense exercise with muscles that are already warm.  

Zone 1 should feel: Easy. A pace you could maintain for a long period of time. Think of walking whilst chatting easily to friends.  

Zone 2- Light: 60 – 70% of MHR. Zone 2 is classed as light, but that can be a bit misleading. We prefer to call it the magic zone because this is where it all happens. 

Working out in zone 2 should feel light, and like you can continue for quite some time at this pace, but it’s also known as the fat burning zone, and exercising in this range offers a lot of benefits.  

This is the best heart rate zone for building overall fitness and endurance (because it’s not excessively hard), and it encourages our bodies to get better at burning fat for fuel. Zone 2 should be an essential part of any workout regime for the average exerciser to reap the benefits listed.  

Zone 2 should feel: Like you’re pushing yourself, but you can still hold a conversation. You should be able to support it for a relatively long time. Think of swimming lengths at a moderate pace, or strength training with plenty of rest in between sets.  

Zone 3- Moderate: 70 – 80% of MHR. When you’re working in zone 3, your heart rate should feel elevated. If you were trying to hold a conversation with someone, you’d need to catch your breath mid-sentence, whereas you’d be able to talk relatively easily in zones 1 and 2.  

Training in zone 3 is good for improving aerobic capability; the function of the heart and the ability of our body to transport oxygen to our muscles. If you’re training for a long event, such as a triathlon or a half-marathon, for example, you’ll want some of your training, around 20 – 30% to be in this zone so that you can work more efficiently in zone 2.  

Don’t make the mistake of spending all your time training here though; you’ll fatigue easily and won’t see as good a result as training mostly in zone 2 as a result. Zone 3 is an ideal place to push yourself into with interval training.  

Zone 3 should feel: Difficult but not like you can’t go on. You should be out of breath and feel like you’re working. Allow yourself plenty of rest and recovery in zone 1 or 2 between intervals. Think of taking part in a HIIT class or running sprints on a treadmill.  

Zone 4- Hard: 80 -90% MHR. When we exercise, we breathe faster as our heart pushes oxygen around the body. This is known as aerobic training, and that’s how we work in zones 2 and 3. 

However, as we push into the top end of zone 3 into zone 4, our muscles need energy faster than the body can give us oxygen, and so we begin to break down glucose for energy instead.  

This is known as anaerobic training and a by-product of it is a build-up of lactic acid in the muscles. This in turn means it’s difficult to maintain zone 4 for very long, because the production of lactate in the muscles forces our body to slow down. 

Zone 4 is not for regular, everyday training unless you’re very fit. However, it does build power in the muscles and teaches our body to tolerate lactic acid better. Because of this, it’s useful for competitive athletes whose events are less than five minutes long, but it can be just as beneficial for endurance athletes as they can learn to push through the painful lactate build-up.  

Zone 4 should feel: Tough, and like you can’t maintain it for long. You should be breathing hard, and not able to hold conversation until you’ve started to recover. Use this zone for short, high intensity bursts coupled with longer, low-intensity recovery.  

Zone 5- Very hard: 90 -100% MHR. Hello Mr Bolt. The very top end of our max heart rate is not where most of us will spend much time. In fact, even top-level athletes don’t push into this zone for long periods of time because the body just can’t handle it.  

Like any heart rate zone, it does have its benefits, particularly if you take part in a sport that requires short, intense bursts of power such as sprinting, long jump, or hurdles. But few of us do.  

There is no reason why you must push yourself into this zone unless you want to. If you do hit over and above 90% MHR, you won’t be able to stay there for long; sixty seconds at the very most, and that will be hard.  

This is not something to try if you’re new to exercising, and it’s a good idea to consult a doctor just to check you’re medically fit enough to push your body to this limit.  

Zone 5 should feel: Extremely hard. You won’t be able to speak properly, just gasp the odd word. Lactate build up is likely to cause pain and a heavy feeling in the muscles. Use this zone if you’re a competitive athlete looking to improve sprint times, or explosive starts.  

The answer to this question primarily depends on how fit you are and what your goals are. The training zones of someone who has been a distance runner for twenty years is going to be vastly different to that of someone brand new to exercise, or an elite sprint swimmer, for example.  

For now, let’s go back to the example of our 63-year-old exerciser. Assuming this person is fit and well, and that they keep an active lifestyle, most of their training can take place in zone 2.  

This would ensure they gain maximum benefit from their exercise sessions in terms of fat burning and keep a healthy circulatory system by making the heart and lungs work. Their exercise sessions could be of a reasonable duration and allow for plenty of recovery between.  

On occasion they might push to zones 3 and 4 to improve their physical condition even more, but it won’t form the bulk of their training regime as pushing your body to those limits actually inhibits results because it hasn’t got time to recover properly.  

Even elite distance runners, such as the Kenyan Women’s athletic team, focus most of their training in zones one and two.  

A 2019 study on UCLA Triathletes confirmed the effectiveness of focusing on heart rate zones for training, noting that the athletes who trained mostly in zone two, pushing into zones three and four, made greater progress and saw better results.  

Following NHS exercise guidelines of 150 minutes of activity a week, spread across the week this might look like a thirty-minute brisk walk (zone 2), a forty-five-minute swim (zone 2), a thirty-minute cross trainer workout with sprints (zones 2,3 and 4), a thirty-minute strength training workout (zone 2), followed by 15 minutes fast run on a treadmill (zones 2 and 3).  

The most important thing to remember is any exercise is better than none. If all your training takes place in zones 1 and 2, that’s perfectly okay and will still be giving you enormous health benefits. If you wear a smart watch or use another form of fitness tracker, then next time you’re working out make a note of your heart rate zones, set the display to show your BPM and you’ll be able to see a whole new insight into your workouts.