Optimizing Performance in the Heat II: Sodium and Sweat
With any topic that involves heat regulation, hydration is part and parcel. On one side of the road, the endurance community has a "fluid plan" where the aim is to prevent dehydration, the dreaded 2%!, while on the other side of the road, "drink to thirst" (of Waterlogged by Tim Noakes ...Hey Tim! BIG fan! Remember me from your one lecture at Wits University where you spoke about your new book "Challenging Beliefs" and signed my copy! See photo at the end of the blog) has also become an equally popular approach.
This blog post explores the relationship between fluid and sodium and offers an introduction to the topic of hydration. It is not intended to be a comprehensive exercise physiology textbook chapter but a starting point that may be further developed in future posts. A Hors d'oeuvre!
But first,
in the previous blog post here. we had the following summary:
The hypothalamus regulates heat and cold responses in the body
The anterior hypothalamus regulates heat response
The posterior hypothalamus regulates cold response
The set point of temperature in the hypothalamus is 37 degrees centigrade
1ml of sweat loss is equivalent to 0.58kcal of energy
Optimal temperatures for road racing are between 10-30 degrees centigrade
Pre-cooling vests have a significant performance-enhancing effect for temperatures above 27 degrees centigrade
Questions we will answer:
1.Fluid Loss and thermoregulation
2.Function, role, concentration of sodium and sweat rates
3.Role of estrogen and progesterone in plasma volume and sodium regulation in Female Athletes
4.Summary
Fluid loss and thermoregulation
In 2007, Sawka and colleagues released a position statement indicating that a 2% body weight loss in fluid could compromise an athlete's performance, emphasizing the importance of drinking to prevent dehydration.
Several years later, Tim Noakes joined the conversation not convinced that maintaining fluid was the answer through his publication Waterlogged (2012), which centered on hyponatremia. Noakes supported a strategy of "drinking to thirst," proposing that athletes should prioritize avoiding hyponatremia rather than fixating on the amount of weight they lose. Hyponatremia is characterized by low levels of sodium in the blood, leading to an increase in the body's water content and subsequent cell swelling. This swelling can give rise to various health issues such as confusion, seizures, and even in some cases coma.
It would seem that somewhere between fluid balance and salt intake is potentially a key idea.
Heat Stress accumulation
Maintaining blood volume is a key determinant of performance. In contrast, maintaining carbohyd