Episode 43: The Science of Sweat | How to Actually Fuel and Hydrate for Endurance with Tash Cooper-Smith

Podcast
Written By Chris Bagg

Sports scientist and triathlete Tash Cooper-Smith from Precision Fuel & Hydration joins The Infirmary to demystify one of endurance sport's most confusing topics: fueling and hydration. Tash breaks down sweat testing, sodium concentration, carbohydrate intake, gut training, and the actual science behind cramping — and why the answer to most athletes' fueling problems is rarely as complicated as they make it. She also shares the story of her own athletic journey, from competitive gymnastics to Kona qualifier in four years, and what that experience taught her about personalizing nutrition for performance.

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Show Notes

If you've ever stood at an aid station mid-race, grabbed whatever was handed to you, and hoped for the best — this episode is for you.

Tash Cooper-Smith is a sports scientist at Precision Fuel & Hydration, the hydration and nutrition company that has been a long-term partner of Campfire Endurance. She holds a Bachelor of Science and a Master's in Sports Nutrition, works with professional and amateur athletes across triathlon, cycling, and ultra running, and is herself a rapid-riser in the sport: four years from her first triathlon to a Kona qualifier slot, with a sub-10 debut Ironman along the way. She also happens to be one of the most practical, no-nonsense voices on fueling you're going to hear.

What this episode covers

The conversation opens with Tash's background — how she moved from competitive gymnastics into triathlon, what her VO2 max looked like as a gymnast versus an endurance athlete (the gap will surprise you), and how working at Precision F&H transformed her own approach to fueling. Her honest account of gut training — including the period where she was plotting run routes near her house in case things went sideways — is equal parts relatable and instructive.

From there, the episode gets into the practical meat of fueling and hydration science. Tash walks through the three things every endurance athlete needs to manage during training and racing: carbohydrates, fluid, and sodium. On carbohydrates, she pushes back on two common extremes — the athlete who thinks a two-hour ride doesn't need fuel, and the athlete trying to match professional intake numbers without the trained gut to support it. The research-backed range of 60 to 90 grams per hour is where most athletes should start, built up gradually and practiced in every session, not just the long ones.

On sodium, Tash explains why Precision F&H's products are formulated at higher concentrations than most competitors — and it starts with the company's founder, Andy Blow, suffering hyponatremia at Kona after drinking water without adequate sodium replacement. The sweat test that followed became the foundation of the company's personalization model. Tash walks through how to interpret your own sweat sodium concentration, what the average looks like across thousands of tested athletes, and how to use that information to dial in your race-day strategy.

The cramping conversation is one of the best in recent Infirmary memory. Tash refuses the easy answer — it's almost never just electrolytes — and instead offers a systematic elimination framework: rule out hydration, then conditioning, then pacing, then caffeine intake. More often than not, she says, the athlete who cramps on the run went too hard on the bike.

The episode closes with a deep dive into heat acclimation: how Precision F&H runs heat sessions in their lab, what physiological adaptations you're actually chasing, and why the maintenance protocol after a heat block is easier than most athletes think.

Tash's closing advice for every endurance athlete: enjoy the small gains instead of fixating on the outcome — and personalize everything, because what works for your training partner may not work for you.

Chris Bagg
Next

Episode 42: Stress + Rest = Growth: A Guided Breathwork Session for Mental Toughness