Exercise Heat Acclimation With Dehydration Does Not Affect Vascular and Cardiac Volumes or Systemic Hemodynamics...

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Cardiovascular Physiology

Background:

• Heat acclimation (HA) improves exercise performance in heat.
• Permissive dehydration may influence HA adaptations.
• Its independent role on cardiovascular function requires investigation.

Purpose of the Study:

• To investigate the independent role of permissive dehydration during exercise HA on vascular and cardiac volumes, ventricular-arterial coupling, and systemic hemodynamics.
• To determine if HA hydration strategy affects thermal and cardiovascular strain during exercise with acute dehydration post-HA.

Main Methods:

• Seven males underwent two 10-day exercise HA interventions: one maintaining euhydration, the other allowing permissive dehydration.
• Experimental trials before and after HA assessed cardiovascular and hemodynamic responses at rest and during cycling in heat.
• Measurements included rectal temperature, heart rate, blood and left ventricular volumes, and systemic hemodynamics.

Main Results:

• Both HA interventions increased sweat rate and power output but maintained core temperature during exercise.
• Neither HA strategy altered resting or exercising blood volume, ventricular volumes, systemic hemodynamics, or ventricular-arterial coupling.
• Post-HA exercise with acute dehydration showed similar thermal and cardiovascular strain regardless of HA hydration strategy.

Conclusions:

• Permissive dehydration during HR-controlled exercise HA does not alter hematological or cardiovascular responses.
• Maintaining euhydration or allowing permissive dehydration during HA yields similar outcomes for exercise in heat.
• The hydration strategy during HA does not influence subsequent exercise responses under moderate heat stress and dehydration.