I did a 4 x 4 interval run on a treadmill today with my FR235. The first few minutes of my warmup the watch recorded way to high HR, I was in HR zone 5 from the beginning. It took 2-3 minutes before the measurements were normal. Is this to be expected and what is the explanation?
Were you using the built-in optical HR? This is normal. The sensor is rarely accurate at high intensity, but the beginning of the workout, before you are warmed up and sweaty is a special challenge for the sensor.
Correct, I use the optical HR sensor. I suspected that it would be inaccurate at very high intensity but was surprised how inaccurate it is in the beginning of a workout, at low intensity. If sweat improves the readings, would it help to rub water on the wrist before the start?
I don't know. You have to try for yourself. Generally optical HR sensors are notorious for their unreliability in some conditions. Some people experience satisfactory results, others don't.
Essentially it has a hard time figuring our HR when it is changing fast - probably throws out some data thinking its noise/junk. Or picks up your strides/cadence as your HR. To ensure a good HR - make sure it is fitting nice and snug, give it some time while holding relatively still to 'lock onto your HR' before final 'start' of your activity. slowly ramp up intensity to hopefully not 'lose' the HR lock. i've never had much luck with my optical however, wife's works well... so most of info is hypothetical from reading/thinking abou it.
I have also this issue. inaccurate optical HR reading at a workout start. So what I usually do is to pre-start, that, is, stay in activity mode during a time until HR stabilises before pushing start button.
Gaby - that is what I was trying to describe - you explained it much easier/better! :-)
Konstantinos - yes even with the HRM Strap the first few minutes can be an issue with very high HR. Usually this is a sign of a few things - static or dry sensors - both of which can be helped with more water when getting band on. A little moisture on tech shirts (or any) to stop static until you get a little sweaty usually helps. This is especially a problem with winter or dry climate workouts. Heart rate electrode gel , aloe vera gel can both add some extended wetness for very easy activities or bike rides.
I have found the wrist monitor is only accurate when I am either asleep or doing somthing like watching TV or pecking at a keyboard. So for any real workout I ALWAYS use a chest monitor.
BTW, I have three optical HR monitors and ALL seem to have the same issues. First, the all take too long to lock in on the Heart Rate. However my Fenix 3 HR is almost tolerable in this regard as it usually take under two minutes to get a lock. As for my 235 or Strava Rhythm Plus, they both take way too long, in the case of my 235 I've seen it take 10 minutes or more and the average is about 7 minutes. The Strava is slightly quicker at 5 minutes but I have had it lose the HR lock on too many occasions to call it useful.
Now, concerning Chest Monitors, of which I have a bit of a collection. In part because I like to have spares on hand and in part because they are sort of like running shoes in that they don't last forever. Biggest issue is sweat migration into the battery recess, causes corrosion and in time you'll find you have a dead sensor. Fortunately these monitors don't cost nearly as much as good running shoes and last a lot longer. Note, plan on replacing them every 18-24 months.
First, keep the straps clean. As in rinse the strap in water after EVERY workout and wash it with the laundry at least once per week. Also unsnap the monitor and wipe it dry of sweat after every single workout. Second, get some Aloe Vera Gel at a local Pharmacy for treating Sunburn. It is a low cost electrically conductive gel that works great for getting good consistent electrical contact and only a small dab on each sensor patch is needed. Note, if you have a Ferrari in your garage and money is not an issue you can also use a Hospital Grade Contact Gel from a Hospital Supply distributor but the price per ounce will shock most of us.
BTW, I am approaching 63 and due to aging skin last fall I was having issues with all of my chest monitors reading flaky due to skin that was too dry to trigger the sensor patches properly. Some days I had to run nearly 1.5 miles before I got enough sweat going to get a good reading. After talking with a local pharmacist about the problem she did some checking and found that Aloe Vera gel was electrically conductive. Since I started using this gel I have not have one single occasion when my chest monitor either went into Runaway or the HR or dropped out. It works, works well, and is also good for your skin.
I only use my watch for running, but I find that prior to my run I turn off and then turn on the HRM in the setup menu wait for the HRM to lock in (the heart icon will stop blinking when its ready) ....I get pretty consistent results.
