Heart rate monitor for weight training

By Andreas B. Diendorfer · ORCID · LinkedIn · Updated 29 October 2026

Short answer

For lifting, a chest strap or an arm band is more reliable in the studies cited than a wrist sensor. In small studies, wrist optical readings were less accurate when the wrist gripped and flexed under load. A strap reads the heart, not the wrist. Beatcast then keeps the number where you can see it between sets.

Last checked: 12 October 2026.

What the studies say

The evidence is small, so I state it plainly and cite where it came from.

A Georgia State University doctoral dissertation (Thomas, 2025) tested wrist and forearm optical sensors in 17 adults aged 18 to 35. They gripped at set fractions of their maximum while pedalling an exercise bike, which is not lifting but loads the hand the same way. Error at a Polar wrist watch was higher than at a Polar forearm sensor, so the comparison covers the location and the device together. The author suggested a forearm location for anyone who needs a precise reading during resistance training.
A group at Southern Utah University and the University of Nevada, Las Vegas compared Garmin Instinct watches with a Polar H10 chest strap in 21 adults doing deadlifts (Kerwin et al., 2025, a conference abstract). The watches showed limited validity, worse at higher intensity and on the inner wrist, and the authors recommended a chest strap.
The same lab tested a Polar Verity Sense worn on the biceps in 20 adults doing deadlifts (Sperry et al., 2025, a conference abstract). It was valid and reliable for average and maximal heart rate at both light and moderately heavy intensity.
A 2017 study of a Polar M600 wrist watch in 36 adults (Horton et al., in Medicine & Science in Sports & Exercise) counted the share of readings within 5 beats per minute of an ECG. It was 34.5 percent in circuit weight training and 91.8 percent in cycling intervals.

These are small samples of young, mostly healthy adults, and some come from the same lab. The figures depend on the device and the exercise. In these studies, steady effort suited the wrist better than lifting did. Where a strap appears, a Polar H10 was the reference, so it is the yardstick and not a finding about arm bands.

Why it happens

An optical sensor reads blood flow under the skin. Gripping and flexing are thought to disturb it. Heart rate also changes fast between sets, and quick changes are harder for optical sensors to follow.

Strap or arm band

A chest strap sits against the ribs, away from the grip. An arm band sits on the forearm or upper arm. In the work above, the arm sensors held up better than the wrist watches did. Beatcast doesn't care where you wear it. The sensor table lists what works, and the Polar comparison covers the common choices.

What to look at between sets

The number lags effort and stays up after it. Watch the direction, not any one value. Heart rate between sets has the full picture, including the rest coach.

Where Beatcast fits

Many lifting apps are built around sets and reps. Beatcast runs next to them, keeps the number on the Lock Screen and in the Dynamic Island while your lifting app is open, and its rest coach times each rest down to a floor you set. A sensor is required. Beatcast on the App Store. Fourteen days free, then one purchase.

Questions

Is a wrist watch bad for lifting?

In the small studies above, the watches were less accurate than a strap or arm sensor.

Do I need a chest strap?

No. An arm band works too.

What number should I rest to?

We don't say. That belongs to a coach.

Does Beatcast work with my lifting app?

It runs alongside it. The Live Activity stays visible.

Good to know

Beatcast is not a medical device. It is built for training and general wellbeing, and it cannot detect, diagnose, treat or monitor any condition. If something about your heart worries you, talk to a doctor rather than to an app.

The Bluetooth word mark is a registered trademark of Bluetooth SIG, Inc. Apple, iPhone, Dynamic Island and Lock Screen are trademarks of Apple Inc. Polar, Garmin and other names belong to their owners and are used only to say which sensors Beatcast can read. Beatcast is an independent product and is not affiliated with, endorsed by or certified by any of them.

Got yours working? Report it in r/beatcast and it goes on the list.