How? Carbs burn at different rates, but the biggest challenge is you can only burn carbs that are stored in your body. At best the watch could take your metrics, make an assumption of the amount of carbs that are stored in your body at the time of your activity and then make another assumption of how many were burned based on your activity.
Try a polar watch like the M2. I did try it and liked it but had to make a choice. The watch will break down carbs, protein and fat after a workout. Pretty cool.
Polar is also making assumptions. This is from their support website:
"It assumes that the availability of glycogen as a source for carbohydrates is limited but that the availability of fat and protein is unlimited. It also assumes that glycogen stores are full at the start of the training session."
I guess if you feel the assumptions are correct, it could be a useful feature, but I personally would be a little wary using the data to make nutritional decisions. Just my worthless two cents. :)
I took a nutrition class when I was working at my university. I think these assumptions are correct. We have unlimited supply of fat. I remember seeing the graph of what nutrients is used depending on your heart rate. I tried the watch for a couple of weeks. It got power from my power meter and would give me a muscle load. But I really did not know what to do with it. Same with the nutrients break down. It was cool to see but doing the same cycling workout generated around the same values. It is a cool watch though. I like their sleep and recovery algorithm. The thing is that I do not want to wear 2 watches. They do not have training effect metric that I use a lot.
Yep. I feel you. But that made me fall in love with indoor cycling on a smart trainer. Something I would not have done if my gym had not close. I could ride outside though but roads are not safe.
the thing is that if you take too much carbs or protein, the unused portion is converted into fat.
carbohydrates is limited but that the availability of fat and protein is unlimited.
Protein is the last of the macro-nutrients to be turned into fuel and then usually only in times of starvation. To all intents and purposes it is not a consideration for energy provision during exercise.
Fat or carb use for energy can be estimated from heart rate during exercise; it's something we have students calculate during exercise physiology classes. Basically at around 70% HRmax you're on 60/40 fat/carb, at 95%HRmax 5/95, and HRmax you're 100% carbs. Knowing your calorie burn you can then estimate how much fat/carbs was consumed during the exercise bout - 1g Fat ~ 9kCal (37kJ), 1g Carb ~ 4kCal (17kJ).
As noted, protein as an energy source can be ignored.
