Posted June 9, 2011 by
Samer H.
We're making some changes to the Fitness Level, which is as good a time as any to explain a bit about it.
The Fitness Level uses the energy you've expended across all exercises to arrive at an estimate of your overall fitness. It also accounts for your body mass, requiring you to do work in proportion to your weight to maintain a given Fitness Level. While the algorithm is quite a bit more sophisticated, you might think of it as a moving average of your fitness.
To do this, we need to calculate work done per exercise, and it turns out that accurate, specific information about that is scarce. The most commonly cited numbers come from the Compendium of Physical Activitites. However, its values for strength training activities are woefully unspecific. It's also possible to estimate caloric burn by calculating the energy needed to move a weight. This is problematic, too, as the efficiency of energy conversion varies between people, and higher intensity exercise results in signifiant additional caloric consumption due to muscle repair and building.
Our algorithm sifts through all this, and now that we have material usage data we're able to see how it's panning out. When we look at the caloric consumption implied by our data (above), it suggests that strength training results in only 1/4 the consumption per hour that cardio exercise does. Based on the available data, we believe that number should be in the range of 50-60% (and we welcome any references to help refine that estimate). Consequently, we have adjusted the constants used in our algorithm to significantly increase the consumption attributed to strength training.
You will notice this change in two ways. First, you will earn more points for strength training than before; second, if you do a lot of strength training your Fitness Level may increase. Depending on the type and intensity of cardio you do, the opposite may be true for cardio exercises.
Finally, all other things being equal we favor a healthy mix of activities, and in particular between strength and cardio. Going forward, the Fitness Level will slightly reward people who pursue a mixed program, as opposed to only doing one type of activity.
That's probably a bit too technical for most folks, and not nearly technical enough for some. Apologies to the former group if this was boring or opaque, and to the latter group if you have questions or thoughts just let us know. We want the Fitness Level to be a simple, meaningful metric and are more than open to suggestions for improvement.
The Fitness Level uses the energy you've expended across all exercises to arrive at an estimate of your overall fitness. It also accounts for your body mass, requiring you to do work in proportion to your weight to maintain a given Fitness Level. While the algorithm is quite a bit more sophisticated, you might think of it as a moving average of your fitness.
To do this, we need to calculate work done per exercise, and it turns out that accurate, specific information about that is scarce. The most commonly cited numbers come from the Compendium of Physical Activitites. However, its values for strength training activities are woefully unspecific. It's also possible to estimate caloric burn by calculating the energy needed to move a weight. This is problematic, too, as the efficiency of energy conversion varies between people, and higher intensity exercise results in signifiant additional caloric consumption due to muscle repair and building.
Our algorithm sifts through all this, and now that we have material usage data we're able to see how it's panning out. When we look at the caloric consumption implied by our data (above), it suggests that strength training results in only 1/4 the consumption per hour that cardio exercise does. Based on the available data, we believe that number should be in the range of 50-60% (and we welcome any references to help refine that estimate). Consequently, we have adjusted the constants used in our algorithm to significantly increase the consumption attributed to strength training.
You will notice this change in two ways. First, you will earn more points for strength training than before; second, if you do a lot of strength training your Fitness Level may increase. Depending on the type and intensity of cardio you do, the opposite may be true for cardio exercises.
Finally, all other things being equal we favor a healthy mix of activities, and in particular between strength and cardio. Going forward, the Fitness Level will slightly reward people who pursue a mixed program, as opposed to only doing one type of activity.
That's probably a bit too technical for most folks, and not nearly technical enough for some. Apologies to the former group if this was boring or opaque, and to the latter group if you have questions or thoughts just let us know. We want the Fitness Level to be a simple, meaningful metric and are more than open to suggestions for improvement.
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