Should You Run Twice a Day? The Science Behind Running Doubles

Running twice a day sounds serious, but is it actually right for you? This week, Zoë and TJ dig into the full science of doubles: what they are, what they're definitively not, and how to know if you're actually a candidate. Plus, a round of listener-submitted Hot or Nots and a great question about why early morning runs feel so much harder.First up, meet Coach James Nance, a multi-sport specialist who coaches cyclists, runners, and skiers through big goals without burning them out. He's based in Fort Collins and has a knack for athletes navigating injury cycles, overtraining, and RED-S. If any of that sounds like your situation, reach out at [email protected], a deep-dive Hot or Not round featuring listener submissions: inversion tables (the effects last minutes, not months), muscle scraping (the original theory has been pretty much debunked), CBD and THC cream (weak evidence, real anti-doping risk), and Superfeet insoles (a rare instance where the research actually delivers, prefab orthotics perform as well as custom at a fraction of the cost).Before the main topic, TJ answers a listener's question about why Zone 2 feels brutally hard at 5 a.m., and it turns out it's not just you. Core temperature, sleep inertia, cortisol, glycogen state, darkness, and cold all compound to inflate your RPE before you've even hit the first mile. There's real science here, and real solutions.Then: doubles. An elite running a morning threshold session and an afternoon shakeout is doing something fundamentally different than a recreational runner cramming two hard efforts into a day. Zoë and TJ break down the physiology of why doubles work when they work (hint: PGC-1α, mitochondrial biogenesis, and aerobic signaling), who's actually a candidate, the gray zone trap, the ego trap, and why energy availability is non-negotiable if you're going to add volume this way. Bottom line: doubles are a tool, not a trophy.