Brady Holmer knows a lot about running and a lot about science: a perfect combo for a conversation on the show. Brady is a lifelong endurance athlete who competed in cross country and track at the collegiate level. He currently works as a science writer and researcher, holding a Master’s degree in human performance. He also recently ran his PR in the marathon: a 2:37. In this episode, Brady and I talk about: The flexibility of heart rate zones and their impact on training adaptations Physiology is constantly fluctuating: zones aren’t static RPE (rating of perceived exertion) is a valuable metric for runners The 80/20 rule of running: 80% lower intensity and 20% higher Benefits and nuance of Zone 2, Zone 3, and Zone 4 Zone 3 training is complicated, but not pointless When to ignore heart rate during runs Maintaining intensity during hot weather Running in summer heat leading to higher heart rates and increased cardiovascular drift Heat acclimation and its benefits for runners (and also cooler weather benefits) Bike intervals for adaptations and injury prevention Finding optimal running paces You know that friend you have who won’t stop talking about Zone 2? Send them this episode now. Links & Resources from the Show: Brady on Twitter/X Brady on Instagram Brady’s Substack VO2 Max Essentials Book Get the free injury prevention email series. Thank you DrinkLMNT! A big thanks to DrinkLMNT for their support of this episode! They make electrolyte drinks for athletes and low-carb folks with no sugar, artificial ingredients, or colors. They are offering a free gift with your purchase at DrinkLMNT. And this does NOT have to be your first purchase. You’ll get a sample pack with every flavor so you can try them all before deciding what you like best.  DrinkLMNT’s products have some of the highest sodium concentrations that you can find. Anybody who runs a lot knows that sodium, as well as other electrolytes like magnesium and potassium, are essential to our performance and how we feel throughout the day. If you’re not familiar, LMNT is my favorite way to hydrate. They make electrolytes for athletes and low-carb folks with no Sugar, artificial ingredients, or colors. I’m now in the habit of giving away boxes of LMNT at group runs around Denver and Boulder and everyone loves this stuff. Boost your performance and your recovery with LMNT. They’re the exclusive hydration partner to Team USA Weightlifting and quite a few professional baseball, hockey, and basketball teams are on regular subscriptions. So check out DrinkLMNT to get a free sampler pack and get your hydration optimized for the upcoming season. Thank you to 2Before! We are supported by 2Before, a powerful sports supplement made from New Zealand Blackcurrants designed to increase endurance, manage inflammation, support immunity, and promote adaptation. 2Before helps to boost performance by increasing blood flow, making it more efficient for the body to pump oxygenated nutrient-rich blood into the muscles.  So, if you want to try to boost your performance and immune system, use code JASON for 30% off 20 packs and multi-serve packs at 2Before.com. Thank you to 2Before for supporting Strength Running! Thank you MOBO Board! Invented by renowned physical therapist Jay Dicharry, MOBO helps you stabilize your stance with an innovative rocker board that’s set up on two fins. The design effectively forces you to drive your big toe into the board to improve your stability. I was pretty arrogant going into my first session on the MOBO Board. How hard can it be to balance, right? Well, I was humbled pretty quickly! Even if you’re a good runner, better balance, stability, and proprioception is going to help you have a more powerful stride and prevent more running injuries. You’ll learn how to improve the efficiency of the kinetic chain from your hip to your big toe. Because as Jay likes to say, it’s not just how strong you are, but how well you use that strength. I was recently at a weekend