Swimming, laps, freestyle, fast

[iAmErika]

The MET (Metabolic Equivalent) value for this activity is 10.

A MET - or Metabolic Equivalent - is defined as the ratio of the work metabolic rate to the resting metabolic rate. One MET is defined as 1 kcal/kg/hour and is roughly equivalent to the energy cost of sitting quietly.

The weight I have entered in my profile is 198.9 lbs. When I perform this activity for 10 minutes, I burn approximately 150 kcal.

Therefore swimming, laps, freestyle, fast is 902 kcal in 1:00. 

However, FitBit records my swim activity data as:

SWIM 15:08, Wednesday December 18, 2019
2075m 01:06:36 mins
3'14"/100 m
307 cals

The difference here is approximately 600 kcals!   

I've raised the issue with FitBit Support but they haven't responded.  

I checked my calculations in a dietary application I trust before I published this post.

[Dominique]

Indeed, here is what the Compendium of Physical Activities report for various forms of swimming:

This site refers to "fast swimming" as being 75 yards per minute, which is also what’s found above for "crawl, fast speed" (btw, what’s the difference between "freestyle" and "crawl"? I was under the impression they were the same in practice).

75 yards is about 69 meters, so 75 yards per minute is about 4.1 km/h. You reported 2075 km for about one hour. As a poor swimmer myself, I find it very impressive someone can swim for 1+ hour straight, but it’s "only" half what is considered "fast speed" (according to the MET tables).

Still, 300 calories for 1+ hour of swimming sounds like you were "short-changed". Fitbit would likely give you more than that for one hour of leisurely walking (which would be far less demanding). To me, this just shows how tricky it is to estimate energy expenditure with an activity tracker.

Anyway, if you’re using calories burned reported by Fitbit as a weight management tool (based on your posting to this forum), what really matters are calories reportedly burned over the entire day. Many people find their Fitbit tends to overstate that number. In your case, it could well be the calories underestimated while swimming help make total daily calories closer to reality.

[Glenda]

@iAmErika  I don't think this is very clearly presented.  Maybe @Dominique  can figure out exactly what you mean but more complete sentences would help.  When you say "when I perform THIS activity..... is that sitting quietly or swimming?   2075m  what is the m here?  3'4"  ?  usually 3' would indicate 3 feet and 4" would be 4 inches.  ???    Fitbit support may never respond.

[Dominique]

@Glenda : 3'14"/100 m = 3 minutes 14 seconds average time per 100 meters (she’s likely swimming in an Olympic pool, which is 50 meters long). This is consistent with a total distance of 2075 meters in 01h06m36s. Yes, I know metric units can be confusing for Americans 😀.