Chest Heart rate strap

Generally, in many cases a chest strap is more accurate than an optical sensor.

You don't have to use a garmin strap. Any ANT+ strap will do. And I think that bluetooth straps are supported as well, but I'm not 100% sure about that.

hello
I have this one and I'm satisfied with it

https://www.amazon.fr/Garmin-010-10997-07-Ceinture-Cardio-Fr%C3%A9quencem%C3%A8tre-Textile/dp/B00BI9X1QM/ref=sr_1_5?__mk_fr_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=SY9AQ4RPZADP&keywords=garmin+ceinture+cardio-fr%C3%A9quencem%C3%A8tre&qid=1558788633&s=gateway&sprefix=GARMIN+CEINTURE%2Caps%2C227&sr=8-5

It morks very well with my Instinct.

Through research and personal experience, I'd say a chest strap is more accurate then any optical sensor in every case.  I can't think of one instance where it would be the other way around. 

From my personal experience, cases when a chest strap can perform worse than an optical HR:

• A chest strap is old and deteriorated.
• A chest strap is inadvertently worn improperly (too loose, for example).
• A dry chest strap is worn in dry and cold conditions can give completely nonsensical readings until warmed-up while in the same conditions an optical HR can give something better
• A chest strap is used in an environment where electromagnetical interference occurs, causing dropouts of external sensors.

• It goes without saying if a chest strap is old or deteriorate it would perform worse. 
• Any HR monitor (chest or OHRM) worn improperly will perform poorly. 
• Yes, a dry chest strap in those conditions will perform poorly. An OHRM performs even worse in those conditions.  
• Electromagnetic field???  Who's working out there?  I have run near power stations and underneath high tension power lines. No problems. 

As, I stated earlier, I can't think of a single instance where an oHRM out performs a chest strap.  If you wish, I can post links to references that confirms this.  All thing's being equal (no more nonsense about worn straps, wearing the strap wrong, dead batteries, or any other obvious problems), please show just one legitimate reference where an OHRM performs better. I have read many post in these forums where people claim their oHRM works just as well as a chest strap.  I question this after reading and understanding countless documentation available on the the shortcomings of the oHRM. You would definitely be the first to suggest the oHRM out perform a chest strap in any manner. 

One important difference between the Optical Heart Rate Monitor (OHRM) and a chest HRM is the chest HRM measures electrical pulses near the chest while the OHRM measures optical differences in the blood vessels.  One metric that is becoming more and more important to measure is Heart Rate Variability (HRV).  This is used to evaluate stress, recovery, etc.  The OHRM is not capable of measuring HRV, but the chest HRM is.  When an OHRM is used, the HRV is estimated, not measured; while the chest HRM uses an actual measurement.

So, yes. A chest HRM is not only more accurate, but provides more useful data than an OHRM.

I recommend "CooSpo H6"  it's cheap and good.  you can search in Aliexpress.com  (I use for 3-4 month ago)

Gee, I did not mean to go into such a discussion, just wrote some remarks from my own experience. None of it I had made up, all these things happened to me. Below some comments to clarify what I meant exactly.

It goes without saying if a chest strap is old or deteriorate it would perform worse.

The optical sensor does not deteriorate the same way as a chest strap. This means that one day you may find out that your chest strap does not perform satisfactorily anymore, whereas if you used the optical sensor instead you could have gotten better results.

Any HR monitor (chest or OHRM) worn improperly will perform poorly.

Sure, but I have the impression that it is easier to wear the optical sensor properly than a chest strap. Proper fitting of a chest strap requires some hassle and especially for a skinny person may be non-trivial to fit the strap to remain comfortable and not slip down during hard effort. I think this is why many people still prefer to use the optical sensor even if it is less accurate, An example from my experience: I used a chest strap during a race. I fitted it as best as I could and yet after about 10 minutes it slipped down. Needless to say the resulting data was useless, and if I used the optical sensor instead I would get perhaps something not 100% perfect, but still better than data from my chest strap.

Yes, a dry chest strap in those conditions will perform poorly. An OHRM performs even worse in those conditions.

Yes, in many cases. But not always, simply because in these conditions poor performance of different sensor types has different physical reasons.

Electromagnetic field???  Who's working out there?  I have run near power stations and underneath high tension power lines. No problems.

Perhaps bad phrasing. Sorry about that, English is not my native language. A relatively strong radio transmission in the 2.4 GHz range can interfere with ANT+ transimission. ANT+ transmission is very weak and it does not take high power to jam it. Does not have to be a high-tension power line. I've read reports here on this forum that for example some gym equipment can interfere.

I have read many post in these forums where people claim their oHRM works just as well as a chest strap.  I question this after reading and understanding countless documentation available on the the shortcomings of the oHRM. You would definitely be the first to suggest the oHRM out perform a chest strap in any manner. 

I never claimed that an optical HR sensor is generally better than a chest strap. Again, perhaps bad phrasing. I would never recommend using an optical sensor in cases where accuracy is essential. I was merely trying to point out - based on my personal experience and just for the sake of argument - that in some rare instances an optical sensor could give better results - whatever the reason - than a chest strap.

I had just read another post in a different thread with such stupid comments it put me in "confrontation mode" when I came across yours. I took it the wrong way and spouted off when I shouldn't have. I apologize and I hope there's no hard feelings. 

No hard feelings at all. On second thought I kinda regreted posting in the first place, because even if my comments were theoretically correct, they have very little practical meaning, and could have been source of confusion.