Exercise - Weights - do I pause? (Fitbit Surge)

[Markie89]

Hit Fitbit users 🙂

I have a question, when at the gym lifting weights with my buddy I select exercise/weights.

Do i pause the workout in between sets when resting?

Just wanted to make my stats on the dashboard as accurate as possible.

Thank you for any replies 🙂

Mark

[Heybales]

If interested in HR stats - like did I have the strength to push the HR just as high as normal - then you can review that later anyway, so no pausing needed.

If interested in decent calorie burn estimate - then doesn't matter, because HR-based calorie burn for non-steady state anaerobic exercise is totally inflated anyway - wrong application of the formula.

Pausing it during the rests would actually inflate it even more.

Should manually log it anyway.

The name on the workout is purely for convenience sake for reviewing later, and to not turn on GPS. It doesn't apply some special calorie burn formula - unless it actually skips doing HR based and is purely at a more correct 3.5 x resting calorie burn per minute.

Might review an activity record you did already. If the calorie burn in your daily 5 min graph is a steady block of calorie burn, and it's about 3.5 x the sleeping calorie burn - then that's what they did.

I'd be curious to know - because it's well known fact for HRM makers that the only valid use of HR-based calorie burn formula is steady-state aerobic exercise. 

The problem is most HRM makers have no idea what you are actually doing, but in this case, by selecting an activity - Fitbit does, and could be smarter about it.

[Colinm39]

@HeybalesExcellent post. I answered a similar post today but I kept out of "steady state" exercise.

I was more interested in the 20% higher calories I get because I believe the Fitbit HR's use a default Vo2Max, and with me, because of my low RHR, that inflates my calories burned on my HR Fitbits by 20% against my Polar which I have set with my correct Vo2max.

Again, well posted because it helps many think outside of the square.

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@Heybales wrote:

If interested in HR stats - like did I have the strength to push the HR just as high as normal - then you can review that later anyway, so no pausing needed.

If interested in decent calorie burn estimate - then doesn't matter, because HR-based calorie burn for non-steady state anaerobic exercise is totally inflated anyway - wrong application of the formula.

Pausing it during the rests would actually inflate it even more.

Should manually log it anyway.

The name on the workout is purely for convenience sake for reviewing later, and to not turn on GPS. It doesn't apply some special calorie burn formula - unless it actually skips doing HR based and is purely at a more correct 3.5 x resting calorie burn per minute.

Might review an activity record you did already. If the calorie burn in your daily 5 min graph is a steady block of calorie burn, and it's about 3.5 x the sleeping calorie burn - then that's what they did.

I'd be curious to know - because it's well known fact for HRM makers that the only valid use of HR-based calorie burn formula is steady-state aerobic exercise. 

The problem is most HRM makers have no idea what you are actually doing, but in this case, by selecting an activity - Fitbit does, and could be smarter about it.

---

[Heybales]

And I've found the Polar models, when set with known HRmax and VO2max - give a calorie burn very close to tested during the VO2max test. So good formula.

I've seen many comment that the Fitbit matched their cheaper Polar that shows no VO2max stat - so I'm guessing Fitbit is using similar formula, which several studies give, even one sponsored by Polar.

But it's the getting of those 2 stats that seems to be the huge bearing on potential accuracy, and we just don't know how Fitbit does it.

Your news tells me that Fitbit is probably reaching a max for level of physical activity.

The other parts of the equation to get good VO2max estimate they can get - restingHR, BMI, amount of exercise weekly. But the formula for that estimate starts losing it at higher levels, and if activity is well above where the chart stops, they miss out. Chart stops at 3 hrs or more of activity weekly, which includes walking, so doing 6 hrs gets no more credit.

I'll mention that the study that Polar at least uses the formula from, and I'm hoping Fitbit saw "fit" (ha!) to use, starts getting worse accuracy for more people for VO2max at about 45 mL/kg/min for men, forgot what it was for women. Bell curve really started flattening and spreading out.

Are you up in that range?

Mine stops at 46, but tested is 57.

http://www.ncbi.nlm.nih.gov/pubmed/16168867

[Colinm39]

@Heybales My issue is that a stress tested Vo2Max on a treadmill when I was 63 was 29 and earlier this year at age 75, the 1 mile Rockport walking test came up with the same result, 29.

If I use the Vo2Max calculator because it uses Resting Heart Rate (RHR) it gives me calories equivalent to using 44 Vo2Max in the  2nd calculator. When I use Vo2Max 29 in this calculator it shows the calorie burn  20% difference.

From that I can only assume Fitbit are using the Vo2Max tables and that is why I get a high calorie burn. That is why I'm using my Fitbit One because those calories are inline with my Polar with my 29 Vo2Max setting.

It does get complicated and for those posting about the high calorie burns on the HR Fitbit models it would be nice to know how Fitbit assess our Vo2Max. A Fitbitter posted yesterday how their HR was high because they were learning to drive.. Result high calories.

Maybe this extract from this link has some bearing and will help others using HR for the calorie efforts.

Extract

HRM Theory

First of all--how do HRMs count calories? First thing is that HRMs do NOT measure caloric expenditure--neither directly nor indirectly. HRMs measure heart rate and that's it. They estimate caloric expenditure during steady-state cardiovascular exercise using the relationship between heart rate and oxygen uptake (or VO2).  

The most commonly accepted method for measuring the calories burned for a particular activity is to measure oxygen uptake (VO2). 

During *steady-state*, aerobic exercise, oxygen is utilized at a relatively consistent rate depending on the intensity of the exercise. There is an observable and reproducible relationship between heart rate and oxygen uptake.When workload intensity increases, heart rate increases and vice versa. 

If we have some individual data--resting heart rate, maximum heart rate, VO2 max, weight--it is possible to make reasonably accurate estimates of caloric expenditure based on the percentage of HRmax or percentage of HRreserve at which someone is working.

For example, we know that 70% of HRmax is equivalent to approx 57% of VO2max. If we know that person's VO2 max is 12 METs and they are working at 70% of HRmax, we can estimate that they are working at (57% x 12 METS) or 6.8 METs. If that person weighs 80 kg, we can estimate that they are burning ~545 Cals/hour (MET value x Body wt in kg). 

The major HRM manufacturers (Polar and Suunto) use much more sophisticated sensing technology and algorithms, but they are still based on the same basic principle--the association of HR to oxygen uptake.  

So, it must be emphasized again: HRMs calorie counts are only accurate when there is a consistent and measurable relationship between heart rate and oxygen uptake.  That means exercises and exercise movements that are aerobic in nature and that are performed at intensities between 40% of VO2 max and the lactate threshold

There are a number of conditions under which heart rate can increase, but without an increase in oxygen uptake:

-Stress, Illness

-Dehydration

-Environment (high heat and humidity)

-Heavy strength training (HR increases because of increased pressure)

-Changes in posture

-Cardiovascular drift during extended aerobic exercise

In other conditions--arm work, overhead work, "anaerobic" or sprint exercise--an HR increase will reflect in increase in VO2, but it is not a consistently measurable and reproducible relationship, therefore the HRM calorie count is not as accurate. 

Note: Certain higher-end HRMs--the Polar RS800 and Suunto T6c use a very sophisticated method of analyzing the R-R interval of heart beat signals. When using this method, it is claimed that they can more accurately estimate caloric expenditure at rest, during anaerobic exercise and even during post-exercise oxygen consumption. Since these models are in the $350-$400 range, I am not including them in this review--if you are interested in more detail, check out www.firstbeattechnologies.com and www.suunto.com