This week, I had the pleasure of working with ultra-runner James Wood as he finalizes his race prep for the Sydney Backyard Ultra next weekend. With a big goal of hitting 160km in 24 hours, we focused on one of the most critical (and often overlooked) aspects of endurance performance: hydration and electrolyte strategy. James has an impressive endurance engine, but in past events, he’s faced a frustrating and painful challenge—severe cramping, especially in the latter stages of races. Despite sticking to popular off-the-shelf electrolytes, the results just weren’t lining up with the demands of his body. That’s where the sweat test came in. Understanding His Physiology During today’s session, we measured James’s individual sweat sodium concentration, which revealed that he loses a significantly higher amount of sodium in his sweat than standard formulas account for. This is a crucial insight, especially in ultra-endurance events where fluid and sodium losses compound over time. With this data in hand, we built a customized hydration strategy tailored to his physiology and racing goals. The New Plan: Precision Fueling with PH 1500 Based on the results, James will be using PH 1500, a high-strength electrolyte drink specifically designed for athletes with higher sodium losses. Unlike generic hydration products, PH 1500 delivers 1,500mg of sodium per litre—giving James a better chance at staying on top of hydration, reducing the risk of cramping, and maintaining performance deep into the race. Together, we mapped out a plan to balance fluid intake, sodium, and fueling throughout each backyard loop to keep his system running smoothly for the full 24 hours. Looking Ahead With his hydration strategy now aligned with his sweat profile, James is heading into the Sydney Backyard Ultra with more confidence and control. No more guesswork—just a solid plan designed to go the distance. Wishing James the best of luck next weekend. Can’t wait to see him hit that 160km mark and run strong, smart, and cramp-free!