It's hot out. As Eugene Morris Jerome said in Neil Simon's Biloxi Blues:
"It's like Africa hot. Tarzan couldn't take this kind of hot."
How can someone tolerate this heat better? The right amount of sodium and water. In a 2012 research study from Scandinavia (when does it ever get that hot in Scandinavia?), water was compared to water and varying amounts of sodium.
Ninety minutes before exercise, participants ingested 10 mL of water/kg body mass either alone or with approximately one or two teaspoons of salt. Participants cycled for 2 hours at low-moderate intensity immediately followed by a time-trial.
After 2 hours of exercise, plasma volume dropped by 10% with 2 tsp of sodium, 12% 1 tsp of sodium 16% without sodium. The drop in plasma volume is likely from sweat loss.
Pre-exercise ingestion of salt plus water maintains higher plasma volume during dehydrating exercise. Sodium and water do not keep the cyclist cooler. However, the sodium smoothie maintains cardiovascular function and improves cycling performance.
To figure out how many milliliters of fluid you need, divide your weight in pounds by 2.2 and multiply by 10. A large 24 oz water bottle is approximately 700ml.
Add 1 tsp of sodium from regular salt
Ingest 90 minutes before exercise.