Most gym treadmills, watches and cardio machines show you a heart rate in beats per minute, usually with a coloured zone beside it. It looks scientific, but many people do not know what the numbers are for. Used well, heart rate is a simple tool for making sure your hard days are hard enough and your easy days are easy enough.
What your heart rate tells you
Your heart beats faster during exercise to deliver more oxygen to working muscles. The harder you work, the higher the number climbs, until you reach your maximum heart rate. That ceiling is mostly set by genetics and age, not by fitness, and it does not tell you how fit you are.
What does change with fitness is your resting heart rate and how fast the number rises at a given effort. A fitter person usually has a lower resting rate, often somewhere between 50 and 70 beats per minute, and recovers faster after exercise. Resting rate varies widely among healthy adults, so treat your own trend as more useful than a comparison with a friend.
Estimating your maximum heart rate
The best way to find your true maximum is a supervised test, which most people do not need. A common estimate is 220 minus your age. A 30-year-old would get 190. Another, often a little more accurate for adults, is 208 minus 0.7 times your age, which gives about 187 for the same person.
These formulas are averages, and individual maximum values can be 10 or more beats away. If a number from a formula feels wrong during a hard effort, trust your breathing and effort over the formula. You can also track the highest rate you actually see during a hard interval session, with a doctor's clearance if you have any health concerns.
The 5 zones in plain language
Zones are simply bands of your maximum heart rate. Names and cut-offs vary by device, but the usual 5 look like this.
- Zone 1, 50 to 60 percent. Very easy. A relaxed walk or warm-up. You can sing.
- Zone 2, 60 to 70 percent. Easy and steady. You can hold a conversation in full sentences. This is the base-building zone.
- Zone 3, 70 to 80 percent. Moderate. Breathing is noticeable, and you can speak in short phrases. Often called the grey zone.
- Zone 4, 80 to 90 percent. Hard. Words come out 1 or 2 at a time. You can hold this for minutes, not hours.
- Zone 5, 90 to 100 percent. All out. Only sustainable for seconds to a couple of minutes.
For a 30-year-old with an estimated maximum of 190, zone 2 sits at roughly 114 to 133, and zone 4 sits at roughly 152 to 171.
What each zone does for you
Zones 1 and 2: the base
Easy aerobic work builds the heart's capacity to pump more blood per beat, grows the small blood vessels in muscle and improves how well your cells burn fat. It is gentle on joints and easy to recover from, so you can do a lot of it. A brisk walk to the office, a gentle jog or an easy bicycle ride often falls here.
Zone 3: useful, but easy to overdo
This pace feels productive, so people drift into it on every run. It is tiring enough to need recovery but not hard enough to drive the largest gains. A bit of it is fine, especially for events like a 10 km race, but if all your sessions land here you may stall.
Zones 4 and 5: the sharp end
Hard intervals raise your maximum oxygen uptake, which is the ceiling on how much oxygen your body can use. Examples include 4 rounds of 4 minutes hard with 3 minutes easy, or 8 to 10 rounds of 30 seconds all out with 90 seconds rest. These sessions are powerful, but also tiring, so a couple per week is plenty for most people.
A sensible weekly mix
Many endurance coaches suggest something close to 80 percent of your training time easy and 20 percent hard. You do not have to follow it exactly, but it is a good starting idea, since most people train too hard on easy days and too easy on hard days.
A sample week for someone aiming for general fitness might look like this:
- Monday: 40 minutes easy jog or brisk walk, zone 2.
- Wednesday: 30 minutes mixed session with 5 rounds of 3 minutes hard (zone 4) and 2 minutes easy.
- Friday: 45 minutes easy cycling or swimming, zone 2.
- Saturday: Long walk or hike, 60 to 90 minutes, zones 1 to 2.
- Strength training on 2 other days, which also counts toward the weekly guideline.
The WHO recommends at least 150 minutes of moderate activity a week, or 75 minutes of vigorous activity, or a mix of both. Zone 2 and 3 work counts as moderate, and zones 4 and 5 count as vigorous.
Things that push your heart rate around
Heart rate is a noisy signal. Do not treat a number as gospel.
- Heat and humidity. On a hot Kampala afternoon your heart rate will run higher for the same pace, because your body is diverting blood to the skin to cool you down. Slow down and judge by effort.
- Dehydration. A drop in fluid raises heart rate at the same effort.
- Poor sleep, stress and illness. All can raise resting and exercise heart rate. If your morning resting rate is up by 7 to 10 beats for several days, take it easy.
- Caffeine and medication. Coffee and some tablets, including some for blood pressure, change your numbers. If you take medication, ask your doctor which zones are suitable for you.
- Wrist sensors. Watches that read from the wrist can lag or miss at high intensity. A chest strap is more reliable if accuracy matters.
The talk test, when you have no device
You do not need a gadget. If you can talk comfortably in full sentences, you are in the easy range. If you can only manage short phrases, you are in the moderate range. If you can say a few words, you are near the top. It is a free, reliable guide.
If you ever feel chest pain, dizziness, unusual breathlessness or an irregular heartbeat during exercise, stop and see a doctor. This matters most if you have a family history of heart problems or are returning to exercise after a long break.
Key takeaways
- Heart rate zones are bands of your maximum heart rate, and 220 minus your age is only a rough estimate.
- Zone 2 is the easy, conversational zone, and it builds your aerobic base with little stress.
- Hard intervals in zones 4 and 5 raise your fitness ceiling, but 2 a week is usually enough.
- Heat, sleep, dehydration and stress all move your heart rate, so judge by effort as well as numbers.
- The talk test is a good free check, and unusual symptoms during exercise deserve a doctor's visit.
