Originally Posted by
colnago62
It picks the best 20 minute block of time you have done. It doesn’t know if that was assisted or not or other factors. It is a good place to start, however. As I said previously, a rider should find which type of test gives them their best numbers stick with it for most consistent results.
Except the context is getting an accurate estimate of FTP, wherein it's already been noted that a 20-min block is difficult to pace properly in the best of conditions. Garmin's automagical calculation is anything but, and definitely not useful for getting a better estimate than what carbonfiberboy has done, for example. It basically "works" only if one just happens to ride their hardest for just the right length of time. Which for me hasn't happened in over a year, even as I've trained and improved my FTP significantly.