I’ve been trying to track calories in/out to manage my weight, but I’m getting such wildly different numbers for my runs that it makes it impossible to know if I’m over- or under-eating. I weigh 119, ran 3 hours today, and wore my Garmin 910xt and hrm. It said 1607 calories, and I uploaded to TP which says 2736. I tried other calculators, and get numbers in between those, most on the higher end. I only recently began using the hrm with my Garmin, prior to using the hrm I was getting much higher numbers from my Garmin. A range of 1000+ calories makes eating a total guess.
I know that Garmin is supposed to have this fabulous hr algorithm, I read DCRainmaker’s review about how it works, but how reliable have people found it? I don’t want to compromise my recovery by undereating.
How far did you run? There are several studies that say the first-order determinants of calorie burn when running are the distance you cover, and your weight.
A starting rule of thumb, according to Runner’s World, is 0.63 net calories per pound per mile (above your base metabolic rate). So if you covered 20 miles (for instance), your net calorie burn would be 1411. They say total calorie burn is 0.75 cal/pound/mile, for 1680.
http://www.runnersworld.com/weight-loss/how-many-calories-are-you-really-burning-0?page=single
The FirstBeat algorithms used in the 910 and other sports watches are also supposed to help estimate the additional benefit of Excess Post-exercise Oxygen consumption… the accuracy of all of these methods is dependent on how close you are to their model, and the only way you can figure that out is to have an actual metabolic test done to figure out how much oxygen you process as you exercise in the first place, and what the various thresholds for aerobic and anaerobic work are.
100 calories per mile. It really does depend on your metabolism, your pace, your weight, etc, but if you figure 100cals per mile, you won’t be that far off, and you won’t over-estimate.
21.3 miles. So, according to the Runner’s World formula, it would be 1901cal gross, 1597 net. The garmin number is close to the net.
I know metabolic testing is ideal, but it isn’t going to happen, I’m not in a position to do so at this time. In the meantime, I have to find something workable.