Originally Posted by
bruce19
This interests me just 'cause I like stuff like this. I don't have a power meter but I do post on Garmin, Strava and a site called
FitDay - Free Weight Loss and Diet Journal. In addition, I have in the past used formulas from various on line sites that are associated with places like the Mayo Clinic and other medial organizations. And, I have a couple books on the subject including ones that address training issues for older athletes. All of them take into consideration age, gender, weight, effort (including mph and climbing) and using a variety of them always yields results that are fairly similar. Here's an example for the 50 mi. ride I referenced. This was 50 mi. w/3,000 of elevation at 14.5 mph. As I recall, riding time was around 3:15. And, my personal data would be Male, 70 yrs. old at 190 lbs. Calories burned according to :
Garmin...2995
Strava...2847
FitDay... 2884
This tracks pretty closely with the formulas I've gotten in books and on line. So, compared to using a power meter all of these can be off in a major way?
Yes.
As other posters have noted, the 1708 kj from Strava is a good estimate. The others are likely 69-75% high.
Some authorities use MET Metabolic Equivalent of Task which are supposed to scale with your weight. That's wrong for riders above their ideal weight because on flatter terrain most of your energy is going into overcoming aerodynamic drag which doesn't increase with weight. It's wrong because aerodynamic drag is less than proportional to weight.
The basic METs are also way off for some reason.
Gadgets based on heart rate can also be off by a factor of two.