The be-all-and-end-all of cycling is POWER and FTP. I like to cycle but no where near enough to warrant buying a power meter for my bike, however I do run enough to get a power meter for my feet, and that's what I've done. I splashed out on a STRYD power meter. It arrived this morning and took about 10 minutes to setup, update and connect to my phone and Garmin Forerunner 735XT, just before heading out for my run today. It's too early to tell if this is any good and if running by power is a good way to train but I'm certainly open to experimenting. Will run with it as an additional bit of info gathering until after Boston and will then start looking into training by power to see how it goes. Who knows, my next PB may be power-based.