No matter how much I train in the heat, I never develop good heat tolerance. This was true even when I was young, had only 12% body fat, and competed in marathons, triathlons and bicycle road races. Must be the Swedish genes. I suffer when the starting temperature in the desert gets 70 or higher.
With my fused back, I try to limit my fluid on Skyline to 3 liters/quarts. On warmer days, I'll hyperhydrate by pounding down a liter of water right before I leave the museum. That gives me four liters. Stashing water is also great provided some jerk doesn't steal it -- this happened to my friend Gunny Walt back in 2007.
Other than dehydration (losing over 2% of body weight from sweating), the primary cause of muscle cramps is loss of sodium.
I am a salty sweater -- my clothing is covered with white patches after a hot hike. I use a higher sodium sports drink (Gatorade Endurance) but there are other options -- Salt Stick, carrying fast food salt packets (1/4 teaspoon of table salt), carrying table salt (one teasponn provides 2000 mg of sodium), NUUN or using some other electrolyte replacement product that has ample sodium. Be aware that many electrolyte replacement products (e.g. Endurolytes) don't provide enough sodium.
Many of my hiking buddies limit their salt intake due to having a predisposition towards high blood pressure or another medical issue where restricting salt helps. Unfortunately, these same friends are more likely to cramp on hikes. Most sslt that one consumes during a hike will be excreted in sweat and thus not increase blood pressure.
The average amount of sodium lost in two pounds of sweat is ~800 mg, almost one gram or 1/2 teaspoon of table salt. Salty sweaters like me can lose even more sodium, regardless of fitness or heat acclimation. If someone loses 1 pound of sweat per hour on Skyline and takes 6 hours, they can realistically lose 3 grams of sodium or 1 and 1/2 teaspoons of table salt.
Other than dehydration (losing over 2% of body weight from sweating), the primary cause of muscle cramps is loss of sodium.
Miles of smiles,
Ellen
