The Run Smarter Podcast Re-Run: Understanding Sweat Science, Hydration & Cramping with Andy Blow (Dec, 2021)
Mar 1, 2026
Andy Blow, founder of Precision Hydration and former elite triathlete, specializes in sweat science and individualized hydration. He explores sweat testing, how sodium loss varies between people, and practical ways to measure sweat rate. Conversations cover cramping causes, electrolyte strategies, gut training for gels, and hydration challenges in cold conditions.
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Andy’s Breakthrough Sweat Test Story
- Andy Blow discovered his own performance collapse in hot races was due to extreme sweat sodium loss after a hospital sweat test.
- The test showed he was in the top 5–10% for sodium loss, which let him calculate targeted replacement and stop collapsing in races.
Hydration Advice Has Swung Like A Pendulum
- Hydration advice swung from 'don't drink' to 'drink as much as possible' then to 'drink to thirst', showing pendulum shifts in science and practice.
- Each extreme has harms: underdrinking causes performance collapse; overdrinking risks hyponatremia and even deaths in endurance events.
Measure Sweat Rate With Before And After Weighing
- Do a simple sweat rate test by weighing yourself before and after a training session and accounting for fluid consumed to estimate liters per hour.
- Repeat across conditions to build your sweat-rate range and decide if you need aggressive hydration.