In the PF&H Labs with Emily Arrell and Dr. Lindsey Hunt

Welcome to episode 357 of the Löw Tide Böyz - A Swimrun Podcast!

What happens when two swimrunners pull on their wetsuits and run for an hour on a treadmill in a heat lab? This week we find out. On our way to ÖTILLÖ, we stop at Precision Fuel & Hydration headquarters for a day and a half of sweat testing. We bring on two of the scientists who ran the show, Emily Arrell and Dr. Lindsey Hunt from the PF&H sports science team. Emily started at Precision as an intern and now advises athletes across triathlon, ultrarunning and swimrun on fuel and hydration. Lindsey holds a PhD in environmental physiology from the University of Sydney and focuses on heat stress, heat training and predicting sweat rates.

The headline result: Chris's lighter suit, mostly swimwear material on the back, bumps his sweat rate about 20% above predicted. Chip's full neoprene suit pushes his close to double. From there we get into why sweat rate and sweat sodium concentration are two separate numbers, how the 2% body mass threshold works, and what happens to heart rate, pace and cramping as you slide past it. Lindsey also makes the case that core temperature, not sweat rate, may be the better thing to watch in a sport that swings between cold water and hot run legs.

We also talk heat acclimation, from multi-block protocols for Kona-bound athletes to a simple layered-up zone two run you can do at home, plus how long those adaptations last. Emily walks through how she adjusts a plan when sweat losses outpace what anyone can realistically drink, why salty sweaters can preload with more sodium, and where the "you don't need electrolytes" internet takes go wrong. We wrap with caffeine timing across an 11-hour race and what the PF&H team learned surveying athletes at the world championships in Nice.

Before the interview, we preview ÖTILLÖ Swimrun Austin, our seventh year in a row at Pace Bend Park. We also give a shout-out to friend of the show Dr. Yael Schonbrun, whose new book Why Don't You Understand Me? is out now. Huge thanks to Emily, Lindsey and the whole crew at Precision Fuel & Hydration for hosting us.

Enjoy!

That's it for this week's show. If you are enjoying the **Löw Tide Böyz**, be sure to subscribe to the show on your favorite podcast player and leave us a five-star rating and review since that's the best way for people to discover the show and the sport of Swimrun. You can find us on **Apple Podcasts**, **Spotify**, and on **YouTube**. Check out our **website** for Swimrun resources including gear guides, tips, how-to videos and so much more. Also make sure to check out our meme page **@thelowtideboyz** on Instagram. If you have any suggestions for the show or questions for us, send us a dm or an email at **lowtideboyz@gmail.com**. Finally, you can support our efforts on **Patreon**...if you feel so inclined.Thanks for listening and see you out there!Chip and Chris