The effect of fluid ingestion on stress hormones during prolonged exercise in the heat

Introduction

Human beings can survive in extreme conditions such as high altitude and extreme cold and heat. These different conditions have various effects in all body functions. Human beings are exposed to a wide range of stimuli that influence homeostasis. During exercise performance in the heat, one of physiological aspects that should be considered is the effect of fluid ingestion in stress hormones. Therefore, alterations in stress hormones are important for performance during prolonged exercise in the heat.

The purpose of this study was to investigate in the effect of fluid ingestion on stress hormones during prolonged exercise in the heat (Temperature 32C, relative humidity 61 3%).

Methods

For this, bicycle ergometer exercise was performed by eight healthy male college students. When water was not ingested, the performed the bicycle ergometer exercise under the conditions 60% VO2max for 120 minutes. When water or carbohydrate-electrolyte fluid was ingested, they performed the exercise at the same intensity and time. Fluid was ingested respectively in different amounts every fifteen minutes. Venous blood samples were drawn at different timepoints- before, during, and after the exercise session.

Results

The results of the study were summarized as follows.

1. The most increase in the level of ACTH was observed when water was not ingested. The least was observed when carbohydrate-electrolyte fluid was ingested.
   
2. The most increase in the level of cortisol was observed when water was not ingested. The least was observed when carbohydrate-electrolyte fluid was ingested.
   
3. The difference in the level of epinephrine among these treatments was not seen.
   
4. The difference in the level of norepinephrine among these treatments was not seen.
   
5. The level of ACTH was increased during exercise in all treatments.
   
6. The level of cortisol was increased during exercise in all treatments.
   
7. The level of epinephrine was increased during exercise in all treatments.
   
8. The level of norepinephrine was increased during exercise in all treatments.

Discussion/ Conclusions

The results of this investigation suggested that the level of stress hormones in the blood was increased more when water was not ingested than when water or carbohydrate-electrolyte fluid was ingested. There was no relationship between fluid ingestion and assessing times. These results suggested that fluid ingestion during prolonged exercise in the heat was required for physiological and biochemical stability and homeostasis of human body.