From trial and error to precision, this episode unpacks why knowing how salty a sweater you are can unlock better fueling, hydration, and performance.

Episode Description: 

Most runners know when their legs are tired, when their heart rate is higher than they'd like, and when their watch disagrees with reality, but far fewer know what’s actually happening in their sweat. And yet, hidden in those grains of salt is a story about performance, cramping, gut trouble, bonking, and why two athletes with identical race fuel and hydration plans can do the same race with wildly different outcomes.

In this episode of Legwork, Matt and Molly talk with Andy Blow — endurance athlete, sports scientist, and founder of Precision Fuel & Hydration, to explore the messy, fascinating world of electrolytes.

From Andy’s own battles with hypernatremia to the science behind sweat testing, the conversation pulls apart the myths, marketing, and misunderstandings that keep athletes guessing. It’s a journey from personal experiment to practical insight, showing how something as simple as knowing your sweat composition can reshape your entire fueling strategy and help you be a more informed athlete.

Whether your kit dries white after every run or leaves almost nothing behind, this episode helps you understand why it matters and how your electrolyte losses can guide smarter fueling and hydration.

They cover:

• ​Andy’s winding path from triathlon to sports science to founding Precision Fuel & Hydration
• ​Why two athletes can lose tenfold different amounts of sodium — and why that matters
• ​How sweat testing works, what it reveals, and why most athletes only need to do it once
• ​The “t-shirt sizing” analogy for understanding your own sweat salinity
• ​How electrolytes influence fuel absorption, cramps, GI distress, and race-day performance
• ​The philosophy behind separating fuel from hydration — and why combination products aren’t always ideal
• ​Real-world examples of hydration strategies, from short runs to Western States-level heat
• ​What 2:1 vs. 1:0.8 carb ratios actually mean, and when those differences matter
• ​The differences between hypotonic, isotonic, and hypertonic drinks
• ​Why marketing oversimplifies hydration — and how to navigate the noise
• ​Research connecting sweat composition to bone mineral density
• ​Finding a healthy relationship with data, wearables, and metrics
• ​Future innovations in sports nutrition — from packaging to apparel to carrying fuel more comfortably

Whether you're training for your first 10K or trying to solve the mystery of mid-race cramps, this episode helps you understand your physiology — and build a hydration strategy that actually fits.

Chapter List: 

00:00 Introduction to Precision Fuel and Hydration

03:09 Andy's Personal and Professional Career Path

05:41 Andy Blow's Athletic Journey and Founding Story

06:26 The Science Behind Sweat Testing and Electrolyte Needs

09:26 Growth and Evolution of Precision Fuel and Hydration

12:38 The Impact of COVID-19 on Business Strategy

16:11 Philosophy of Separation in Fuel and Hydration Products And the Myth That None of It Matters

20:56 The Role of Electrolytes in Performance

23:53 Insights from Formula 1 Experience

26:51 The Importance of Sweat Testing for Athletes

27:13 Getting Into The Science Of It All, T-Shirt Sizing The Salinity Of Your Sweat And The Case For Seeking Out That Information

37:38 Hydration Strategies for Athletes

42:35 Understanding Carbohydrate Ratios in Fueling

50:13 The Science of Osmolality in Sports Drinks

53:57 Evolving Beliefs in Sports Nutrition

59:01 Andy's Research on Sweat Salinity and Bone Health

01:03:37 The Role of Data in Athletic Performance

01:08:37 Future Innovations in Sports Nutrition and Gear