Sleep, stress, and dehydration can all raise or lower heart rate on any given day, which makes heart rate training less accurate than we’d like.   That’s why co-founder and lead engineer of Stryd Jamie Williamson decided it was time for a change.   With his business partner Li Shang and a team of like-minded “sports nuts”, Jamie set out to create the world’s first wearable power meter for running.   Stryd understands how fast you can run and how long you can run by measuring energy output three dimensionally.   Its unique environmental sensors measure your movements - including forward and back, side to side, and up and down - to determine how fast, how far, and how efficiently you can run across any terrain.   And that’s not even the best part.   It collects this data at lab grade power to give you real-time, actionable target numbers that let you know how efficiently you’re running and make reaching your goals a whole lot simpler.   Listen in as Jamie discusses how Stryd works and why power is quickly replacing heart rate training. Questions Jamie is asked: 2:57 What prompted you to start Stryd and how has the process been so far? 7:39 How did you become interested in producing technology for runners and cyclists to train more efficiently? 9:49 How does Stryd differ from other devices like GPS watches? 13:52 What is ‘power’ as a unit of measurement? 21:07 What are the inherent issues with training by heart rate and how is Stryd more accurate? 26:37 What exactly is ‘critical power’ and how does it relate to lactate threshold and/or VO2 max? 27:49 Can someone simply determine their critical power from a 10k race? 29:25 Are other tests for critical power available on your website? 30:31 How does Stryd help runners with running efficiency, form and injury prevention? 34:19 When you're testing for inefficiencies with Stryd, do you get real-time feedback? 36:25 How compatible is Stryd with other technology? 39:37 Will Stryd ever be able to measure environmental factors such as wind? 41:50 What else is Stryd focusing on right now? Quotes by GUEST: “We have report after report after report of personal bests that people were getting where they were up against the wall and this technology allowed them to identify weaknesses that they could work on.” “Computing real-time pace is extremely difficult...When you’re in a car and you use your GPS, you can actually use it as a speedometer, but that’s just because the signal is so huge. You’re changing large amounts of position over short amounts of time because you’re going fast in a car, and it’s the opposite when running.” “Power is useful because it’s the only independent, objective measure of running performance,. It’s not impacted by any other things.” “You start the race with a full battery - that’s how much energy you have to spend in that race. Given the duration of the race, at the very end you want the battery to be empty. You don’t want it to be negative, you don’t want to leave some stuff on the course where you still have some energy to spare….You want to have nothing left at the end, and power is the way to do that.” “I will say a lot of people do use heart rate as kind of a safety measure. They’ll look at ‘What is my max heart rate that I want to stick to today and I don’t want to go above?’, and they’ll use it in that way to make sure they’re not overdoing it.”   Take a Listen on Your Next Run   Want more awesome interviews and advice? Subscribe to our iTunes channel   Mentioned in this podcast: Stryd website Stryd Facebook community Follow Stryd on Twitter We really hope you’ve enjoyed this episode of Run to the Top. The best way you can show your support of the show is to share this podcast with your family and friends and share it on your Facebook, Twitter, or any other social media channel you use. If more people who know about the podcast and download the episodes, it means I can reach out to and get through to the top running influencers, to bring them on and share t