Totally, a great idea for fitness!
In our statistical model, we actually have a measurement called fitness. It is mapping hours of exercise to how muscular a body will be which is learned from really world data. We are planning to expose this measurement in the future!
Yes! We are working hard on perfect + consistent measurements. Here is a quick overview:http://imgur.com/ndgq2Ci
And this feature will be released in API really soon. Stay tuned!
