Do you need a chest strap heart rate monitor?

The question is about your training, not your watch

People usually arrive at this question having decided their watch is bad. Almost always it is not: the watch is doing something genuinely difficult — inferring a pulse from light scattered through a moving wrist joint — and it does it well in some conditions and badly in others. Which conditions is now documented.

The 2025 Sensors study tested 28 participants across rest, a cycling warm-up, burpees and a modified Bruce treadmill protocol, with a Polar H10 as the reference. The pattern is consistent and it is about intensity change rather than intensity: steady work is handled well, transitions are not.

Question one: do you do intervals?

If a typical week includes structured intervals, hill repeats, circuits or any session where your heart rate is supposed to swing hard and recover, buy a strap. This is where the published evidence is unambiguous — during the burpee protocol every optical device tested fell below 0.50 concordance, and a wrist-worn Garmin Forerunner 55 showed a bias of approximately 33 bpm, the largest error in the paper.

Thirty-three beats is not a rounding error. It is the difference between a zone-4 rep and a zone-2 rep, which means it is the difference between a training plan and a random number generator.

Question two: do you actually use the number?

Plenty of people watch pace and effort, and look at heart rate afterwards out of curiosity. If your training decisions do not change based on the heart-rate number, an expensive improvement to that number buys you nothing. Be honest here — it is the single most money-saving question on this page.

Question three: will you wear it?

A chest strap is less comfortable than a watch. Some people forget they are wearing one; others find it intolerable over long durations. An ECG strap that lives in a drawer measures exactly nothing, and a wrist sensor you wear every day beats it comprehensively.

If you know yourself well enough to know the strap will not happen, there is a middle option with real evidence behind it: an optical armband. The Polar Verity Sense recorded the lowest resting error of any device in the same study and a bias under 0.1 bpm on the treadmill protocol — because the forearm is a better sensor site than the wrist, not because it is a better sensor. Our full review covers both halves of that result.

Question four: what do you already own?

This is where the money argument gets decisive. A strap costs around a hundred dollars and works with the watch you already have, over Bluetooth or ANT+. A new watch costs several times that and — this is the part people are not told — does not fix the problem at all, because it reads optically at the wrist exactly like the old one.

If your complaint is heart rate, upgrading the watch is the expensive way to be disappointed twice. That is the entire argument of the heart-rate upgrade path, and it is the most useful thing on this site for the money.

The case for not buying one

We should make this argument properly, because most pages in this category will not.

If you run steady, ride steady, and use heart rate as a rough guide rather than a prescription, wrist optical is fine and the research supports that. The failure modes are concentrated in transitions and explosive work. Adding a device to your routine has a real cost in friction, and friction is why people stop tracking altogether.

Buy the strap because your training needs it, not because a spec sheet made you feel your data was inadequate.