Garmin accuracy.

For discussions about bikes and equipment.
Psamathe
Posts: 11575
Joined: 10 Jan 2014, 8:56pm

Re: Garmin accuracy.

Postby Psamathe » 16 Apr 2020, 12:17pm

My 1030 has recently started telling my "Estimated Sweat Loss" and the numbers were shocking (particularly as it has temperature sensors, climb rate, my body metrics, etc. available).

The numbers it giver are pretty consistent between 55 and 75 ml per mile.

So today I weighed myself, went for a ride, drinking and eating nothing, got back and immediately weighed myself again and Garmin 1030 said Est. Sweat Loss 1.4L (on a 24 mile ride) but weight loss from before and after weights was only 600 gm.

Ian

User avatar
Mick F
Spambuster
Posts: 50342
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Garmin accuracy.

Postby Mick F » 16 Apr 2020, 2:02pm

I take the calories info with a pinch of salt too. Sweat loss? How does it know how much sweating you've done?

There's no way that a device on the handlebars can know how much energy you put into a ride. The fitter and stronger you are, the less the effort required. Having a HR monitor can help, but I still think it's pure guesswork.
Mick F. Cornwall

Psamathe
Posts: 11575
Joined: 10 Jan 2014, 8:56pm

Re: Garmin accuracy.

Postby Psamathe » 16 Apr 2020, 4:00pm

Mick F wrote:I take the calories info with a pinch of salt too. Sweat loss? How does it know how much sweating you've done?

There's no way that a device on the handlebars can know how much energy you put into a ride. The fitter and stronger you are, the less the effort required. Having a HR monitor can help, but I still think it's pure guesswork.

The calories my device gives (or "estimated calories) seems to generally be around the same as others on here have posted and other online cycling "calorie calculator" web sites give. Of course that does not make it correct but consistent. But as for ascent/descent for a ride, I think the main use of the numbers if for comparison with other rides from the same device (e.g. do a ride of 1000 Cal and another of 1500 Cal so 2nd is 1½ times the first).

I did reflect on Calories used calculated on the device last summer on tour struggling into a strong headwind for 40 miles - Garmin just saw a flat slow ride whereas I was completely exhausted! (but undoubtedly made up for it with a nice following wind for entire ride on some other ride)

Ian

User avatar
Mick F
Spambuster
Posts: 50342
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Garmin accuracy.

Postby Mick F » 16 Apr 2020, 4:12pm

Yes Ian, I'm with you on this.
So long as the info is consistent, it means something, and it eventually evens out.

Sometimes the calorific figure is more than the recommended daily intake for a normal health adult. This is just for a two or three hour ride!
Do a four or five hour ride and it's double what a normal health adult male should eat.

Where do they get these figures from?

Recommended daily intake for a bloke is 2,500Kcals.
I can clear that figure in 50miles ........... so that means to stay stable, I need 5,000Kcals just for that single day!
I don't think I can eat that much.
Mick F. Cornwall

Psamathe
Posts: 11575
Joined: 10 Jan 2014, 8:56pm

Re: Garmin accuracy.

Postby Psamathe » 16 Apr 2020, 4:19pm

Mick F wrote:Yes Ian, I'm with you on this.
So long as the info is consistent, it means something, and it eventually evens out.

Sometimes the calorific figure is more than the recommended daily intake for a normal health adult. This is just for a two or three hour ride!
Do a four or five hour ride and it's double what a normal health adult male should eat.

Where do they get these figures from?

Recommended daily intake for a bloke is 2,500Kcals.
I can clear that figure in 50miles ........... so that means to stay stable, I need 5,000Kcals just for that single day!
I don't think I can eat that much.

Without suggesting it "right" or "wrong" I do find it useful to help push me to eat more, particularly on tour riding longer distances with load most days. Last summer I was away for 2 months/2000 miles and I eat loads and when I got home I'd lost 8 Kg weight! I have heard others say how much they eat when touring (chatting to other cyclists stopping same campsite). But as to numbers, I'm no dietician. But maybe somebody do some maths, large piece of cake, several pints, fry-up for breakfast, etc.

Ian

User avatar
Mick F
Spambuster
Posts: 50342
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Garmin accuracy.

Postby Mick F » 16 Apr 2020, 7:59pm

Cake and a fry-up seems normal to me. :D

We all have different metabolisms.
Some folk are "portly" and some less so, and it's not much to do with input/output.
Mick F. Cornwall