Current hydration guidelines are erroneous

… Dehydration does not impair exercise performance in the heat.

I want to thank Rob and Trevor for the kind review they put forth on some of the research I’ve been involved with over the years, as presented in their recent podcast (episode 263). For what its worth, I give them an A+.

Perhaps the most controversial part of the podcast would be towards the end when they shift to discussing the hydration research my team conducted, published in BJSM. I’m wondering what others feel about the industry standard 2% body weight cut-off rule for hydration when it comes to exercising in the heat?

@PaulLaursen, can’t tell you how much that means! Really appreciate your listening and glad you enjoyed the episode. It was a lot of fun recording it! Looking forward to getting you on the show

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Just a note on hydration status during exercise, especially in high temperatures. It’s very interesting to me that time trial performance does not seem to be affected negatively by partial dehydration. I would not have guessed that.

However, I think that looking only at athletic performance (power, speed, etc.) when partially dehydrated is not the full picture. Consistently not taking in enough fluids during hot rides can potentially lead to kidney stone formation, because it can increase the concentration of stone-forming compounds such as uric acid and calcium oxalate. I don’t know if these concentrations increase enough at a 2% dehydration level, or if it you have to be more dehydrated than that. But believe me, you do not want kidney stones. Ask me how I know! See Assessment of the pathogenetic role of physical exercise in renal stone formation - PubMed

Also, I’m wondering what effect dehydration has on mental motivation, and how that would affect performance. So, if a rider is dehydrated will they attack as hard on that last hill or breakaway in the last 15km?

Related: Don’t miss our Exercise in the Heat Pathway as the spring heats up!

Dave Trendler
Fast Talk Labs