What are the signs of dehydration during exercise?

During exercise, dehydration can manifest itself through several physiological signs, and the presence of thirst, dry mouth, and fatigue are key indicators of this condition. When the body loses fluids, it triggers the thirst response, which is a vital mechanism to encourage fluid intake and maintain hydration levels. A dry mouth often accompanies thirst, signifying that the body is lacking sufficient water. Fatigue is another common symptom, as dehydration can impact muscle function, energy levels, and overall physical performance.

In contrast, the other choices present signs contrary to what typically happens in a dehydrated state. Increased energy and focus suggest a well-hydrated and energized body, which is not aligned with dehydration. A low heart rate and calmness may imply a relaxed state but do not indicate hydration status, particularly since dehydration usually raises heart rate due to increased cardiovascular strain. Likewise, the presence of clear urine and enhanced performance reflect proper hydration rather than dehydration, as a well-hydrated body typically produces clear urine and supports optimal physical function.