Heart Rate Accuracy During Weight Training and Tabata

[JiujitsuBlue]

Hi, I've just recently started to use my Charge 2 after a year of neglect. I am feeling frustrated and concerned about inaccurate heart rate readings during workouts. For example, when I go on a brisk walk with my dog, I would get strong steady readings of about 115 bmp, burning a good rate of about 5 calories per minute. However when I put in more strenuous work such as tabata workouts and weight training, I am out of breath but heart rate would only register not more than about 100, resulting in low calorie burn. I regularly take the band off to wipe the sweat off, however really frustrated that it is not giving me accurate results. Hoping to get some advise from others who may have experienced this problem and have found good solutions.

[t.parker]

Weight training usually is a challenge for most wrist-based HR monitors because such activity involves lots of wrist movement but not only. The exercise itself may block or reduce blood flow and this is what the watch is actually measuring. This is a very common problem. You may try to improve it by wearing the watch higher so it will not be affected by wrist bending but it doesn't guarantee accuracy. In general, for weight training, I'd rather use a chest strap than wrist HR.

[JiujitsuBlue]

Thank you! I will give it a try and strap it to my chest.

[Heybales]

Since you mention calories burned as one desire of accuracy - the formula used for HR-based calorie burn (all HRM use a formula, there is no direct measurement of calories with HR) is only valid for steady-state aerobic exercise.

Not anaerobic, not intervals.

Lifting and Tabata are both.

So inflated calorie burn is the result of that formula, especially if it had correct HR seen.

Now if you are very active otherwise and the workouts are 15 min a day - in the scheme of things no big deal even if 100% inflated.

But if long sessions of lifting and not very active otherwise - could be a big deal.

Now perhaps you are totally lucking out and the reduced HR seen causes an inflated calories given with formula for it to produce a decent calorie burn.

But it would be better to just manually log those activities as a Workout Record. You can leave the Activity Record there for seeing the HR, distance, and step info, the calorie burn shown will get replaced with your manual entry.

Weights is the entry to pick, use the start/duration time as shown in the Workout Record, and accept the stated calorie burn.

It's not as high as cardio - and that's exactly true.

That entry is for normal lifting of sets 3-5, and reps 5-15, set rests of 2-4 min.

If this is actually machine-type circuit training of 15-20 reps, and rests up to 1 min - that's Circuit training in the database.

If your Tabata is by treadmill, same thing - but select running and put in the time and distance gone, accept the calorie burn.

If by biking as the original Tabata study protocol - eh, tad harder, but if you are given on the machine a Kj figure - that's calories basically, manually log it. If given an avg Watts figure, still very accurate but need to math it out - Watts x 3.6 x hours (or min/60) = calories.

I'll mention too, the formula for calorie burn from HR is also most inflated near the top of aerobic range, right before going anaerobic, and also at the bottom of aerobic range, right above daily activity level - like walking.

You might just compare, since calories matter for weight loss - log a Workout Record for walking session for distance and time and see what the calculated calorie burn is - that is actually more accurate than HR-based estimate is.

I mention that because if you are correctly trying to eat less than you burn by a reasonable amount, but you aren't actually burning as much as reported - you could easily have no or minimal fat loss.

Oh - comment about using a chest strap was not to attempt to put the wrist-based device there - that likely won't work.

Reference was to a true EKG electrical impulse HR-monitor that uses a chest strap instead.

But again from above - for weight lifting for purpose of calorie burn - not needed and would still cause inflated calorie burn estimate.

If purely curious about HR (which isn't increased for the same reason it increases for cardio), then that is the method.

[Jannie6]

I’m very frustrated with my charge 2. The heart rate is so inaccurate. When I walk 2.0 mph my heart rate was showing as 189-199 so I freaked out and stopped. I bought a polar heart rate strap that is very accurate and it was showing 108-109 at the same time the Fitbit was reading 149-199. I knew the Fitbit couldn’t be right 2.0 is so slow so my heart rate shouldn’t / wouldn’t be that fast.

[MoonstoneWolf]

Fitbit inspire 2.  Not sure how they calculate HR but it showed I was walking at a heart rate of 140 bpm for 45 minutes.  Shouldn't I be huffing and puffing or sweaty if that is the case?

[Heybales]

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@MoonstoneWolf wrote:

Fitbit inspire 2.  Not sure how they calculate HR but it showed I was walking at a heart rate of 140 bpm for 45 minutes.  Shouldn't I be huffing and puffing or sweaty if that is the case?

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HR isn't calculated it's being measured - by a little light hopefully reflecting accurately off some veins/arteries to see the beats of the heart as the blood moves, stops, moves.

It could be you don't read well for HR by this method - manually take your HR for 6 sec and x 10 to compare roughly.

If no where near, misread HR, move device on wrist. (most people have issues the other way - they know it's high, but it reads low)

If close - it's accurate.

Sweaty is if your body needs to cool off from the effort - it may not need to depending on temps and ability to cool, that's why it's bad indicator of level of effort.

Huffing & puffing is if your body needs the oxygen and that's why the HR went high - to supply more oxygen.

HR also goes high to aid in cooling, or from stress (that's why it's not always a great indicator of calculated calories burn - now that is by formula).

But yes, generally if HR is going up it's to supply more oxygen, and therefore breathing rate would go up too - but that doesn't require huffing and puffing - just breathing more frequently or deeper.

You may also have a Honda heart, genetically a higher HRmax than average and it can rev high. Compared to diesel heart where max is low and it stays low even with hard effort.

Start by manual reading to confirm accuracy.

[jamiemac9]

You’re going to strap the Fitbit to the chest? How would that work?