How do you find your max heart rate on Apple Watch?

Where can you see your highest heart rate?

Your Apple Watch measures your heart rate during every workout unless you turned that off^[1]. Your iPhone keeps the readings in the Health app. Two apps help you find your peak.

1. Open the Health app on your iPhone. Tap Browse, then Heart, then an entry such as Heart Rate. Pick a week, a month or a year to see your heart rate across that span^[1].
2. Open the Fitness app. Tap Sessions, pick a workout and tap Show More next to Heart Rate. A graph shows how long that session spent in each of Apple's five zones^[2].

Start in the Health app and find the day with the highest reading. Then switch to the day or hour view to see the readings around that peak^[1].

The Fitness app helps you choose which workouts to check. Apple's zones are a share of your max heart rate^[2]. A session with time in Apple's highest zone is a good one to open in the Health app.

What does a believable peak look like?

A real max comes at the end of a hard push. Your heart rate climbs for minutes as the effort builds. Near the end it flattens out. The NTNU research group behind the HUNT study describes this as a plateau where the heart cannot beat any faster even when the work gets harder^[5].

These are the signs of a real peak.

• It comes in the last minutes of your hardest effort.
• The readings climb to it over several minutes.
• It holds for more than one reading.
• Another hard day reaches close to it.

These are the signs of a sensor spike.

• It jumps straight up from an easy heart rate.
• It shows up on an easy jog or in the first minutes of a run.
• It stays flat on one number for a long stretch while you run.
• No other workout comes close to it.

Apple says the saved data can hold the odd reading that is far too high or too low^[3]. A lone jump like that tells you nothing about your max.

The flat stretch has a known cause. Researchers have described how optical sensors can lock onto the steady rhythm of walking or jogging and count your steps as heartbeats^[6]. The Apple Watch 4 was the one device whose error did not clearly go up in that study's own walking test^[6]. A long flat stretch is still worth a second look.

Read the level the readings held near the end of the effort. Leave out a lone point that jumps above it.

Why is your highest reading below your age estimate?

A max effort runs until you are too exhausted to go on^[5]. Most training sessions end long before that point. Easy runs, tempo runs and even many interval sessions stop short of max.

Take a 45-year-old runner. Tanaka's formula is the age estimate built from the most data. It gives this runner 176.5^[10].

Say the highest reading in a year of runs is 168. One likely story is that no run went all the way. The estimate is the number to use until a harder effort tops it.

Some people do have a max below the formula. A large registry study looked at 4,796 healthy adults who all went all out on a treadmill^[11]. A breathing measure confirmed each effort.

The study's own age formula came out almost the same as Tanaka's. It missed a typical person by about 11 beats^[11]. The statistics put about 19 in 20 people within about 25 beats of it. The authors warned against using an age formula to judge whether someone went all out^[11].

So a peak below the estimate has two possible stories. A run that stopped early is one. A max that runs low is the other.

Only an all-out effort tells the two apart. A lower number from a lab test or a max effort is the one to use. Max heart rate formulas compared shows how far each formula can miss.

How accurate is Apple Watch heart rate during hard efforts?

The Apple Watch came close to a chest strap at max. Abt and colleagues put an Apple Watch on each wrist of 15 people^[7]. Each person then did a lab test until they could not go on. The researchers compared each watch with a chest strap.

They rated the Apple Watch good to very good for measuring max heart rate^[7]. It read neither high nor low on average. The error for a single person was small on one wrist and moderate on the other^[7].

Accuracy drops as effort rises. Thomson and colleagues tested 30 young adults on a treadmill test that went from very light effort to very hard^[8]. The Apple Watch missed a lab heart monitor by 2.4% to 5.1% across the five effort levels. A 5% miss at 180 beats a minute is 9 beats.

The other wrist device in the test missed by 3.9% to 13.5%^[8]. The match got weaker as effort went up for both devices^[8].

A chest strap is the closest thing to lab equipment you can wear. Gillinov and colleagues tested 50 healthy adults on a treadmill, a bike and an elliptical^[9]. A chest strap matched the lab reference best. It scored 0.996 on a scale where 1 is a perfect match.

The Apple Watch came next at 0.92^[9]. Every device but one did well on the treadmill^[9]. The authors say a chest strap is the one to use when an exact heart rate matters^[9].

One reading is not enough to trust. A peak that holds and shows up again on another hard day is the number to use.

How should you wear the watch for a max effort?

Apple says the heart rate reading is most accurate when the watch fits snugly on top of your wrist^[4]. You can tighten the band for the workout and loosen it after. The sensor needs to stay close to your skin.

Some things get in the way of a good reading. Cold weather can drop the blood flow in your wrist skin too low for the sensor to read^[4]. The ink in some tattoos can block the sensor's light^[4]. Steady movement like running reads better than stop-and-start movement like tennis or boxing^[4].

A chest strap helps when the wrist gives poor readings. Apple Watch can connect to a Bluetooth chest strap and take your heart rate from it^[4]. Apple says the optical sensor on the watch covers 30 to 210 beats a minute^[3]. A runner whose max is above 210 would need a strap to see it.

What max efforts do runners use?

The NTNU research group shares a simple max effort that needs only a heart rate monitor^[5].

1. Warm up until you start to sweat.
2. Run two 4-minute intervals hard enough that you are too short of breath to talk. Move easily for 3 minutes between them.
3. Start a third interval. Speed up even more two minutes in, and keep going until you are too exhausted to continue.
4. Your max is the highest heart rate you reach.

Run it on a rested day.

Hard bouts before the final push gave a slightly higher max in one study. Berglund and colleagues tested 108 adults aged 22 to 70 in two ways at least two days apart^[13]. One was an ordinary fitness test that got harder until they stopped. The other test added repeated hard bouts before the final all-out push in the same way as the NTNU test.

The second test's max came out 2.2 beats higher on average^[13]. The authors concluded that people who are not athletes got close to their max in the ordinary test too.

The way a treadmill test climbs moves the number a little. Machado and colleagues had 34 recreational male runners do three treadmill tests that sped up every 1, 2 or 3 minutes^[14]. Their max averaged 181.8 with 1-minute steps, 184.8 with 2-minute steps and 183.1 with 3-minute steps^[14]. The authors suggest 2-minute steps for finding max heart rate.

Both studies found differences of only 2 to 3 beats. A good all-out effort of either kind gets you close.

One good max effort lasts a long time. A study that tracked 132 adults through 908 max tests over 25 years found max heart rate fell slowly and steadily with age^[12]. Training does not raise it either^[5].

Can a race show a higher max than a lab test?

It can. The highest heart rate on a hard interval day averaged 207 in one study of 20 college distance runners^[15]. At a race it averaged 206. Both were above the 194 the same runners reached on a lab treadmill test^[15].

The choice of max changed their training numbers. Breathing starts to pick up sharply at an effort level called the breathing threshold.

For these runners the breathing threshold came at 83.3% of the lab max^[15]. The same heart rate was only 77% of their race or training max. A percent-of-max line moves with the max you use.

The runners were college racers, so the gap may not be the same size for you. Your saved races and hardest interval days are still worth a look, because your watch already holds those peaks.

Type your max in below with your age and sex to see your bands.

Heart rate zones on Apple Watch shows how to set those numbers on the watch itself. The max heart rate calculator gives the age estimate if you have no max yet.

How does Diastra find your max?

Diastra reads every workout your Apple Watch saved in Apple Health and finds your max for you. It looks for the highest heart rate you held across several readings. A second hard session within 8 beats has to back that number up. A peak below the age estimate leaves the estimate in place.

A guided test sets your max at once when it tops both the estimate and the max you already have. A number you type sets your max too, and typing is how a lower measured max gets in. Your max carries a label that says Estimate, Observed, Entered or Verified.

The Zone 2 you know is Diastra's Easy band. Easy, Threshold and VO₂max are all drawn from your max. Every study behind the bands is on how Diastra draws your bands.